png-js - npm Package Compare versions

Comparing version 0.1.1 to 1.0.0

package.json

 {
-  "name": "png-js",
-  "description": "A PNG decoder in CoffeeScript",
-  "version": "0.1.1",
-  "author": {
-      "name": "Devon Govett",
-      "email": "[e-mail]",
-      "url": "http://badassjs.com/"
-  },
-  "repository": {
-      "type": "git",
-      "url": "https://github.com/devongovett/png.js.git"
-  },
-  "bugs": "http://github.com/devongovett/png.js/issues",
-  "devDependencies": {
-      "coffee-script": ">=1.0.1"
-  },
-  "scripts": {
-      "prepublish": "coffee -c png-node.coffee"
-  },
-  "main": "png-node.js",
-  "engine": [ "node >= v0.6.0" ]
-}
+    "name": "png-js",
+    "description": "A PNG decoder in JavaScript",
+    "version": "1.0.0",
+    "author": {
+        "name": "Devon Govett",
+        "email": "[e-mail]",
+        "url": "http://badassjs.com/"
+    },
+    "repository": {
+        "type": "git",
+        "url": "https://github.com/devongovett/png.js.git"
+    },
+    "bugs": "http://github.com/devongovett/png.js/issues",
+    "devDependencies": {
+        "jest": "^24.1.0",
+        "prettier": "^1.16.4"
+    },
+    "scripts": {
+        "test": "jest",
+        "prettier": "prettier test/**/*.js png-node.js png.js --write"
+    },
+    "main": "png-node.js",
+    "engine": [
+        "node >= v0.6.0"
+    ],
+    "jest": {
+        "setupFiles": [
+            "<rootDir>/test/patch-canvas.js",
+            "<rootDir>/zlib.js",
+            "<rootDir>/png.js"
+        ]
+    }
+}

png-node.js

@@ -1,231 +0,280 @@
-// Generated by CoffeeScript 1.4.0
-
 /*
-# MIT LICENSE
-# Copyright (c) 2011 Devon Govett
-# 
-# Permission is hereby granted, free of charge, to any person obtaining a copy of this 
-# software and associated documentation files (the "Software"), to deal in the Software 
-# without restriction, including without limitation the rights to use, copy, modify, merge, 
-# publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons 
-# to whom the Software is furnished to do so, subject to the following conditions:
-# 
-# The above copyright notice and this permission notice shall be included in all copies or 
-# substantial portions of the Software.
-# 
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
-# BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
-# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-*/
+ * MIT LICENSE
+ * Copyright (c) 2011 Devon Govett
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this
+ * software and associated documentation files (the "Software"), to deal in the Software
+ * without restriction, including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+ * to whom the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+ * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
 
+const fs = require('fs');
+const zlib = require('zlib');
 
-(function() {
-  var PNG, fs, zlib;
+module.exports = class PNG {
+  static decode(path, fn) {
+    return fs.readFile(path, function(err, file) {
+      const png = new PNG(file);
+      return png.decode(pixels => fn(pixels));
+    });
+  }
 
-  fs = require('fs');
+  static load(path) {
+    const file = fs.readFileSync(path);
+    return new PNG(file);
+  }
 
-  zlib = require('zlib');
+  constructor(data) {
+    let i;
+    this.data = data;
+    this.pos = 8; // Skip the default header
 
-  module.exports = PNG = (function() {
+    this.palette = [];
+    this.imgData = [];
+    this.transparency = {};
+    this.text = {};
 
-    PNG.decode = function(path, fn) {
-      return fs.readFile(path, function(err, file) {
-        var png;
-        png = new PNG(file);
-        return png.decode(function(pixels) {
-          return fn(pixels);
-        });
-      });
-    };
+    while (true) {
+      const chunkSize = this.readUInt32();
+      let section = '';
+      for (i = 0; i < 4; i++) {
+        section += String.fromCharCode(this.data[this.pos++]);
+      }
 
-    PNG.load = function(path) {
-      var file;
-      file = fs.readFileSync(path);
-      return new PNG(file);
-    };
+      switch (section) {
+        case 'IHDR':
+          // we can grab  interesting values from here (like width, height, etc)
+          this.width = this.readUInt32();
+          this.height = this.readUInt32();
+          this.bits = this.data[this.pos++];
+          this.colorType = this.data[this.pos++];
+          this.compressionMethod = this.data[this.pos++];
+          this.filterMethod = this.data[this.pos++];
+          this.interlaceMethod = this.data[this.pos++];
+          break;
 
-    function PNG(data) {
-      var chunkSize, colors, i, index, key, section, short, text, _i, _j, _ref;
-      this.data = data;
-      this.pos = 8;
-      this.palette = [];
-      this.imgData = [];
-      this.transparency = {};
-      this.text = {};
-      while (true) {
-        chunkSize = this.readUInt32();
-        section = ((function() {
-          var _i, _results;
-          _results = [];
-          for (i = _i = 0; _i < 4; i = ++_i) {
-            _results.push(String.fromCharCode(this.data[this.pos++]));
+        case 'PLTE':
+          this.palette = this.read(chunkSize);
+          break;
+
+        case 'IDAT':
+          for (i = 0; i < chunkSize; i++) {
+            this.imgData.push(this.data[this.pos++]);
           }
-          return _results;
-        }).call(this)).join('');
-        switch (section) {
-          case 'IHDR':
-            this.width = this.readUInt32();
-            this.height = this.readUInt32();
-            this.bits = this.data[this.pos++];
-            this.colorType = this.data[this.pos++];
-            this.compressionMethod = this.data[this.pos++];
-            this.filterMethod = this.data[this.pos++];
-            this.interlaceMethod = this.data[this.pos++];
-            break;
-          case 'PLTE':
-            this.palette = this.read(chunkSize);
-            break;
-          case 'IDAT':
-            for (i = _i = 0; _i < chunkSize; i = _i += 1) {
-              this.imgData.push(this.data[this.pos++]);
-            }
-            break;
-          case 'tRNS':
-            this.transparency = {};
-            switch (this.colorType) {
-              case 3:
-                this.transparency.indexed = this.read(chunkSize);
-                short = 255 - this.transparency.indexed.length;
-                if (short > 0) {
-                  for (i = _j = 0; 0 <= short ? _j < short : _j > short; i = 0 <= short ? ++_j : --_j) {
-                    this.transparency.indexed.push(255);
-                  }
+          break;
+
+        case 'tRNS':
+          // This chunk can only occur once and it must occur after the
+          // PLTE chunk and before the IDAT chunk.
+          this.transparency = {};
+          switch (this.colorType) {
+            case 3:
+              // Indexed color, RGB. Each byte in this chunk is an alpha for
+              // the palette index in the PLTE ("palette") chunk up until the
+              // last non-opaque entry. Set up an array, stretching over all
+              // palette entries which will be 0 (opaque) or 1 (transparent).
+              this.transparency.indexed = this.read(chunkSize);
+              var short = 255 - this.transparency.indexed.length;
+              if (short > 0) {
+                for (i = 0; i < short; i++) {
+                  this.transparency.indexed.push(255);
                 }
-                break;
-              case 0:
-                this.transparency.grayscale = this.read(chunkSize)[0];
-                break;
-              case 2:
-                this.transparency.rgb = this.read(chunkSize);
-            }
-            break;
-          case 'tEXt':
-            text = this.read(chunkSize);
-            index = text.indexOf(0);
-            key = String.fromCharCode.apply(String, text.slice(0, index));
-            this.text[key] = String.fromCharCode.apply(String, text.slice(index + 1));
-            break;
-          case 'IEND':
-            this.colors = (function() {
-              switch (this.colorType) {
-                case 0:
-                case 3:
-                case 4:
-                  return 1;
-                case 2:
-                case 6:
-                  return 3;
               }
-            }).call(this);
-            this.hasAlphaChannel = (_ref = this.colorType) === 4 || _ref === 6;
-            colors = this.colors + (this.hasAlphaChannel ? 1 : 0);
-            this.pixelBitlength = this.bits * colors;
-            this.colorSpace = (function() {
-              switch (this.colors) {
-                case 1:
-                  return 'DeviceGray';
-                case 3:
-                  return 'DeviceRGB';
-              }
-            }).call(this);
-            this.imgData = new Buffer(this.imgData);
-            return;
-          default:
-            this.pos += chunkSize;
-        }
-        this.pos += 4;
-        if (this.pos > this.data.length) {
-          throw new Error("Incomplete or corrupt PNG file");
-        }
+              break;
+            case 0:
+              // Greyscale. Corresponding to entries in the PLTE chunk.
+              // Grey is two bytes, range 0 .. (2 ^ bit-depth) - 1
+              this.transparency.grayscale = this.read(chunkSize)[0];
+              break;
+            case 2:
+              // True color with proper alpha channel.
+              this.transparency.rgb = this.read(chunkSize);
+              break;
+          }
+          break;
+
+        case 'tEXt':
+          var text = this.read(chunkSize);
+          var index = text.indexOf(0);
+          var key = String.fromCharCode.apply(String, text.slice(0, index));
+          this.text[key] = String.fromCharCode.apply(
+            String,
+            text.slice(index + 1)
+          );
+          break;
+
+        case 'IEND':
+          // we've got everything we need!
+          switch (this.colorType) {
+            case 0:
+            case 3:
+            case 4:
+              this.colors = 1;
+              break;
+            case 2:
+            case 6:
+              this.colors = 3;
+              break;
+          }
+
+          this.hasAlphaChannel = [4, 6].includes(this.colorType);
+          var colors = this.colors + (this.hasAlphaChannel ? 1 : 0);
+          this.pixelBitlength = this.bits * colors;
+
+          switch (this.colors) {
+            case 1:
+              this.colorSpace = 'DeviceGray';
+              break;
+            case 3:
+              this.colorSpace = 'DeviceRGB';
+              break;
+          }
+
+          this.imgData = new Buffer(this.imgData);
+          return;
+          break;
+
+        default:
+          // unknown (or unimportant) section, skip it
+          this.pos += chunkSize;
       }
-      return;
+
+      this.pos += 4; // Skip the CRC
+
+      if (this.pos > this.data.length) {
+        throw new Error('Incomplete or corrupt PNG file');
+      }
     }
+  }
 
-    PNG.prototype.read = function(bytes) {
-      var i, _i, _results;
-      _results = [];
-      for (i = _i = 0; 0 <= bytes ? _i < bytes : _i > bytes; i = 0 <= bytes ? ++_i : --_i) {
-        _results.push(this.data[this.pos++]);
+  read(bytes) {
+    const result = new Array(bytes);
+    for (let i = 0; i < bytes; i++) {
+      result[i] = this.data[this.pos++];
+    }
+    return result;
+  }
+
+  readUInt32() {
+    const b1 = this.data[this.pos++] << 24;
+    const b2 = this.data[this.pos++] << 16;
+    const b3 = this.data[this.pos++] << 8;
+    const b4 = this.data[this.pos++];
+    return b1 | b2 | b3 | b4;
+  }
+
+  readUInt16() {
+    const b1 = this.data[this.pos++] << 8;
+    const b2 = this.data[this.pos++];
+    return b1 | b2;
+  }
+
+  decodePixels(fn) {
+    return zlib.inflate(this.imgData, (err, data) => {
+      if (err) {
+        throw err;
       }
-      return _results;
-    };
 
-    PNG.prototype.readUInt32 = function() {
-      var b1, b2, b3, b4;
-      b1 = this.data[this.pos++] << 24;
-      b2 = this.data[this.pos++] << 16;
-      b3 = this.data[this.pos++] << 8;
-      b4 = this.data[this.pos++];
-      return b1 | b2 | b3 | b4;
-    };
+      const { width, height } = this;
+      const pixelBytes = this.pixelBitlength / 8;
 
-    PNG.prototype.readUInt16 = function() {
-      var b1, b2;
-      b1 = this.data[this.pos++] << 8;
-      b2 = this.data[this.pos++];
-      return b1 | b2;
-    };
+      const pixels = new Buffer(width * height * pixelBytes);
+      const { length } = data;
+      let pos = 0;
 
-    PNG.prototype.decodePixels = function(fn) {
-      var _this = this;
-      return zlib.inflate(this.imgData, function(err, data) {
-        var byte, c, col, i, left, length, p, pa, paeth, pb, pc, pixelBytes, pixels, pos, row, scanlineLength, upper, upperLeft, _i, _j, _k, _l, _m;
-        if (err) {
-          throw err;
-        }
-        pixelBytes = _this.pixelBitlength / 8;
-        scanlineLength = pixelBytes * _this.width;
-        pixels = new Buffer(scanlineLength * _this.height);
-        length = data.length;
-        row = 0;
-        pos = 0;
-        c = 0;
-        while (pos < length) {
+      function pass(x0, y0, dx, dy, singlePass = false) {
+        const w = Math.ceil((width - x0) / dx);
+        const h = Math.ceil((height - y0) / dy);
+        const scanlineLength = pixelBytes * w;
+        const buffer = singlePass ? pixels : new Buffer(scanlineLength * h);
+        let row = 0;
+        let c = 0;
+        while (row < h && pos < length) {
+          var byte, col, i, left, upper;
           switch (data[pos++]) {
-            case 0:
-              for (i = _i = 0; _i < scanlineLength; i = _i += 1) {
-                pixels[c++] = data[pos++];
+            case 0: // None
+              for (i = 0; i < scanlineLength; i++) {
+                buffer[c++] = data[pos++];
               }
               break;
-            case 1:
-              for (i = _j = 0; _j < scanlineLength; i = _j += 1) {
+
+            case 1: // Sub
+              for (i = 0; i < scanlineLength; i++) {
                 byte = data[pos++];
-                left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
-                pixels[c++] = (byte + left) % 256;
+                left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
+                buffer[c++] = (byte + left) % 256;
               }
               break;
-            case 2:
-              for (i = _k = 0; _k < scanlineLength; i = _k += 1) {
+
+            case 2: // Up
+              for (i = 0; i < scanlineLength; i++) {
                 byte = data[pos++];
                 col = (i - (i % pixelBytes)) / pixelBytes;
-                upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
-                pixels[c++] = (upper + byte) % 256;
+                upper =
+                  row &&
+                  buffer[
+                    (row - 1) * scanlineLength +
+                      col * pixelBytes +
+                      (i % pixelBytes)
+                  ];
+                buffer[c++] = (upper + byte) % 256;
               }
               break;
-            case 3:
-              for (i = _l = 0; _l < scanlineLength; i = _l += 1) {
+
+            case 3: // Average
+              for (i = 0; i < scanlineLength; i++) {
                 byte = data[pos++];
                 col = (i - (i % pixelBytes)) / pixelBytes;
-                left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
-                upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
-                pixels[c++] = (byte + Math.floor((left + upper) / 2)) % 256;
+                left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
+                upper =
+                  row &&
+                  buffer[
+                    (row - 1) * scanlineLength +
+                      col * pixelBytes +
+                      (i % pixelBytes)
+                  ];
+                buffer[c++] = (byte + Math.floor((left + upper) / 2)) % 256;
               }
               break;
-            case 4:
-              for (i = _m = 0; _m < scanlineLength; i = _m += 1) {
+
+            case 4: // Paeth
+              for (i = 0; i < scanlineLength; i++) {
+                var paeth, upperLeft;
                 byte = data[pos++];
                 col = (i - (i % pixelBytes)) / pixelBytes;
-                left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
+                left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
+
                 if (row === 0) {
                   upper = upperLeft = 0;
                 } else {
-                  upper = pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
-                  upperLeft = col && pixels[(row - 1) * scanlineLength + (col - 1) * pixelBytes + (i % pixelBytes)];
+                  upper =
+                    buffer[
+                      (row - 1) * scanlineLength +
+                        col * pixelBytes +
+                        (i % pixelBytes)
+                    ];
+                  upperLeft =
+                    col &&
+                    buffer[
+                      (row - 1) * scanlineLength +
+                        (col - 1) * pixelBytes +
+                        (i % pixelBytes)
+                    ];
                 }
-                p = left + upper - upperLeft;
-                pa = Math.abs(p - left);
-                pb = Math.abs(p - upper);
-                pc = Math.abs(p - upperLeft);
+
+                const p = left + upper - upperLeft;
+                const pa = Math.abs(p - left);
+                const pb = Math.abs(p - upper);
+                const pc = Math.abs(p - upperLeft);
+
                 if (pa <= pb && pa <= pc) {
@@ -238,81 +287,117 @@ paeth = left;
                 }
-                pixels[c++] = (byte + paeth) % 256;
+
+                buffer[c++] = (byte + paeth) % 256;
               }
               break;
+
             default:
-              throw new Error("Invalid filter algorithm: " + data[pos - 1]);
+              throw new Error(`Invalid filter algorithm: ${data[pos - 1]}`);
           }
+
+          if (!singlePass) {
+            let pixelsPos = ((y0 + row * dy) * width + x0) * pixelBytes;
+            let bufferPos = row * scanlineLength;
+            for (i = 0; i < w; i++) {
+              for (let j = 0; j < pixelBytes; j++)
+                pixels[pixelsPos++] = buffer[bufferPos++];
+              pixelsPos += (dx - 1) * pixelBytes;
+            }
+          }
+
           row++;
         }
-        return fn(pixels);
-      });
-    };
-
-    PNG.prototype.decodePalette = function() {
-      var c, i, length, palette, pos, ret, transparency, _i, _ref, _ref1;
-      palette = this.palette;
-      transparency = this.transparency.indexed || [];
-      ret = new Buffer(transparency.length + palette.length);
-      pos = 0;
-      length = palette.length;
-      c = 0;
-      for (i = _i = 0, _ref = palette.length; _i < _ref; i = _i += 3) {
-        ret[pos++] = palette[i];
-        ret[pos++] = palette[i + 1];
-        ret[pos++] = palette[i + 2];
-        ret[pos++] = (_ref1 = transparency[c++]) != null ? _ref1 : 255;
       }
-      return ret;
-    };
 
-    PNG.prototype.copyToImageData = function(imageData, pixels) {
-      var alpha, colors, data, i, input, j, k, length, palette, v, _ref;
-      colors = this.colors;
-      palette = null;
-      alpha = this.hasAlphaChannel;
-      if (this.palette.length) {
-        palette = (_ref = this._decodedPalette) != null ? _ref : this._decodedPalette = this.decodePalette();
-        colors = 4;
-        alpha = true;
-      }
-      data = (imageData != null ? imageData.data : void 0) || imageData;
-      length = data.length;
-      input = palette || pixels;
-      i = j = 0;
-      if (colors === 1) {
-        while (i < length) {
-          k = palette ? pixels[i / 4] * 4 : j;
-          v = input[k++];
-          data[i++] = v;
-          data[i++] = v;
-          data[i++] = v;
-          data[i++] = alpha ? input[k++] : 255;
-          j = k;
-        }
+      if (this.interlaceMethod === 1) {
+        /*
+          1 6 4 6 2 6 4 6
+          7 7 7 7 7 7 7 7
+          5 6 5 6 5 6 5 6
+          7 7 7 7 7 7 7 7
+          3 6 4 6 3 6 4 6
+          7 7 7 7 7 7 7 7
+          5 6 5 6 5 6 5 6
+          7 7 7 7 7 7 7 7
+        */
+        pass(0, 0, 8, 8); // 1
+        pass(4, 0, 8, 8); // 2
+        pass(0, 4, 4, 8); // 3
+        pass(2, 0, 4, 4); // 4
+        pass(0, 2, 2, 4); // 5
+        pass(1, 0, 2, 2); // 6
+        pass(0, 1, 1, 2); // 7
       } else {
-        while (i < length) {
-          k = palette ? pixels[i / 4] * 4 : j;
-          data[i++] = input[k++];
-          data[i++] = input[k++];
-          data[i++] = input[k++];
-          data[i++] = alpha ? input[k++] : 255;
-          j = k;
-        }
+        pass(0, 0, 1, 1, true);
       }
-    };
 
-    PNG.prototype.decode = function(fn) {
-      var ret,
-        _this = this;
-      ret = new Buffer(this.width * this.height * 4);
-      return this.decodePixels(function(pixels) {
-        _this.copyToImageData(ret, pixels);
-        return fn(ret);
-      });
-    };
+      return fn(pixels);
+    });
+  }
 
-    return PNG;
+  decodePalette() {
+    const { palette } = this;
+    const { length } = palette;
+    const transparency = this.transparency.indexed || [];
+    const ret = new Buffer(transparency.length + length);
+    let pos = 0;
+    let c = 0;
 
-  })();
+    for (let i = 0; i < length; i += 3) {
+      var left;
+      ret[pos++] = palette[i];
+      ret[pos++] = palette[i + 1];
+      ret[pos++] = palette[i + 2];
+      ret[pos++] = (left = transparency[c++]) != null ? left : 255;
+    }
 
-}).call(this);
+    return ret;
+  }
+
+  copyToImageData(imageData, pixels) {
+    let j, k;
+    let { colors } = this;
+    let palette = null;
+    let alpha = this.hasAlphaChannel;
+
+    if (this.palette.length) {
+      palette =
+        this._decodedPalette || (this._decodedPalette = this.decodePalette());
+      colors = 4;
+      alpha = true;
+    }
+
+    const data = imageData.data || imageData;
+    const { length } = data;
+    const input = palette || pixels;
+    let i = (j = 0);
+
+    if (colors === 1) {
+      while (i < length) {
+        k = palette ? pixels[i / 4] * 4 : j;
+        const v = input[k++];
+        data[i++] = v;
+        data[i++] = v;
+        data[i++] = v;
+        data[i++] = alpha ? input[k++] : 255;
+        j = k;
+      }
+    } else {
+      while (i < length) {
+        k = palette ? pixels[i / 4] * 4 : j;
+        data[i++] = input[k++];
+        data[i++] = input[k++];
+        data[i++] = input[k++];
+        data[i++] = alpha ? input[k++] : 255;
+        j = k;
+      }
+    }
+  }
+
+  decode(fn) {
+    const ret = new Buffer(this.width * this.height * 4);
+    return this.decodePixels(pixels => {
+      this.copyToImageData(ret, pixels);
+      return fn(ret);
+    });
+  }
+};

png.js

@@ -1,65 +0,66 @@
-// Generated by CoffeeScript 1.4.0
-
 /*
-# MIT LICENSE
-# Copyright (c) 2011 Devon Govett
-# 
-# Permission is hereby granted, free of charge, to any person obtaining a copy of this 
-# software and associated documentation files (the "Software"), to deal in the Software 
-# without restriction, including without limitation the rights to use, copy, modify, merge, 
-# publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons 
-# to whom the Software is furnished to do so, subject to the following conditions:
-# 
-# The above copyright notice and this permission notice shall be included in all copies or 
-# substantial portions of the Software.
-# 
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
-# BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
-# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
-# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-*/
+ * MIT LICENSE
+ * Copyright (c) 2011 Devon Govett
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this
+ * software and associated documentation files (the "Software"), to deal in the Software
+ * without restriction, including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+ * to whom the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+ * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
 
+window.PNG = (function() {
+  let APNG_DISPOSE_OP_NONE = 0;
+  let APNG_DISPOSE_OP_BACKGROUND = 1;
+  let APNG_DISPOSE_OP_PREVIOUS = 2;
+  let APNG_BLEND_OP_SOURCE = 0;
+  let APNG_BLEND_OP_OVER = 1;
+  let scratchCanvas = document.createElement('canvas');
+  let scratchCtx = scratchCanvas.getContext('2d');
+  let makeImage = function(imageData) {
+    scratchCtx.width = imageData.width;
+    scratchCtx.height = imageData.height;
+    scratchCtx.clearRect(0, 0, imageData.width, imageData.height);
+    scratchCtx.putImageData(imageData, 0, 0);
 
-(function() {
-  var PNG;
+    const img = new Image();
+    img.src = scratchCanvas.toDataURL();
+    return img;
+  };
 
-  PNG = (function() {
-    var APNG_BLEND_OP_OVER, APNG_BLEND_OP_SOURCE, APNG_DISPOSE_OP_BACKGROUND, APNG_DISPOSE_OP_NONE, APNG_DISPOSE_OP_PREVIOUS, makeImage, scratchCanvas, scratchCtx;
-
-    PNG.load = function(url, canvas, callback) {
-      var xhr,
-        _this = this;
+  class PNG {
+    static load(url, canvas, callback) {
       if (typeof canvas === 'function') {
         callback = canvas;
       }
-      xhr = new XMLHttpRequest;
-      xhr.open("GET", url, true);
-      xhr.responseType = "arraybuffer";
-      xhr.onload = function() {
-        var data, png;
-        data = new Uint8Array(xhr.response || xhr.mozResponseArrayBuffer);
-        png = new PNG(data);
-        if (typeof (canvas != null ? canvas.getContext : void 0) === 'function') {
+
+      const xhr = new XMLHttpRequest();
+      xhr.open('GET', url, true);
+      xhr.responseType = 'arraybuffer';
+      xhr.onload = () => {
+        const data = new Uint8Array(xhr.response || xhr.mozResponseArrayBuffer);
+        const png = new PNG(data);
+        if (typeof (canvas && canvas.getContext) === 'function') {
           png.render(canvas);
         }
-        return typeof callback === "function" ? callback(png) : void 0;
+        return typeof callback === 'function' ? callback(png) : undefined;
       };
+
       return xhr.send(null);
-    };
+    }
 
-    APNG_DISPOSE_OP_NONE = 0;
+    constructor(data1) {
+      let i;
+      this.data = data1;
+      this.pos = 8; // Skip the default header
 
-    APNG_DISPOSE_OP_BACKGROUND = 1;
-
-    APNG_DISPOSE_OP_PREVIOUS = 2;
-
-    APNG_BLEND_OP_SOURCE = 0;
-
-    APNG_BLEND_OP_OVER = 1;
-
-    function PNG(data) {
-      var chunkSize, colors, delayDen, delayNum, frame, i, index, key, section, short, text, _i, _j, _ref;
-      this.data = data;
-      this.pos = 8;
       this.palette = [];
@@ -70,15 +71,15 @@ this.imgData = [];
       this.text = {};
-      frame = null;
+      let frame = null;
+
       while (true) {
-        chunkSize = this.readUInt32();
-        section = ((function() {
-          var _i, _results;
-          _results = [];
-          for (i = _i = 0; _i < 4; i = ++_i) {
-            _results.push(String.fromCharCode(this.data[this.pos++]));
-          }
-          return _results;
-        }).call(this)).join('');
+        var data;
+        let chunkSize = this.readUInt32();
+        let section = '';
+        for (i = 0; i < 4; i++) {
+          section += String.fromCharCode(this.data[this.pos++]);
+        }
+
         switch (section) {
           case 'IHDR':
+            // we can grab  interesting values from here (like width, height, etc)
             this.width = this.readUInt32();
@@ -92,3 +93,5 @@ this.height = this.readUInt32();
             break;
+
           case 'acTL':
+            // we have an animated PNG
             this.animation = {
@@ -100,5 +103,7 @@ numFrames: this.readUInt32(),
             break;
+
           case 'PLTE':
             this.palette = this.read(chunkSize);
             break;
+
           case 'fcTL':
@@ -108,3 +113,4 @@ if (frame) {
             }
-            this.pos += 4;
+
+            this.pos += 4; // skip sequence number
             frame = {
@@ -116,5 +122,7 @@ width: this.readUInt32(),
             };
-            delayNum = this.readUInt16();
-            delayDen = this.readUInt16() || 100;
-            frame.delay = 1000 * delayNum / delayDen;
+
+            var delayNum = this.readUInt16();
+            var delayDen = this.readUInt16() || 100;
+            frame.delay = (1000 * delayNum) / delayDen;
+
             frame.disposeOp = this.data[this.pos++];
@@ -124,21 +132,30 @@ frame.blendOp = this.data[this.pos++];
             break;
+
           case 'IDAT':
           case 'fdAT':
             if (section === 'fdAT') {
-              this.pos += 4;
+              this.pos += 4; // skip sequence number
               chunkSize -= 4;
             }
-            data = (frame != null ? frame.data : void 0) || this.imgData;
-            for (i = _i = 0; 0 <= chunkSize ? _i < chunkSize : _i > chunkSize; i = 0 <= chunkSize ? ++_i : --_i) {
+
+            data = (frame && frame.data) || this.imgData;
+            for (i = 0; i < chunkSize; i++) {
               data.push(this.data[this.pos++]);
             }
             break;
+
           case 'tRNS':
+            // This chunk can only occur once and it must occur after the
+            // PLTE chunk and before the IDAT chunk.
             this.transparency = {};
             switch (this.colorType) {
               case 3:
+                // Indexed color, RGB. Each byte in this chunk is an alpha for
+                // the palette index in the PLTE ("palette") chunk up until the
+                // last non-opaque entry. Set up an array, stretching over all
+                // palette entries which will be 0 (opaque) or 1 (transparent).
                 this.transparency.indexed = this.read(chunkSize);
-                short = 255 - this.transparency.indexed.length;
+                var short = 255 - this.transparency.indexed.length;
                 if (short > 0) {
-                  for (i = _j = 0; 0 <= short ? _j < short : _j > short; i = 0 <= short ? ++_j : --_j) {
+                  for (i = 0; i < short; i++) {
                     this.transparency.indexed.push(255);
@@ -149,14 +166,23 @@ }
               case 0:
+                // Greyscale. Corresponding to entries in the PLTE chunk.
+                // Grey is two bytes, range 0 .. (2 ^ bit-depth) - 1
                 this.transparency.grayscale = this.read(chunkSize)[0];
                 break;
               case 2:
+                // True color with proper alpha channel.
                 this.transparency.rgb = this.read(chunkSize);
+                break;
             }
             break;
+
           case 'tEXt':
-            text = this.read(chunkSize);
-            index = text.indexOf(0);
-            key = String.fromCharCode.apply(String, text.slice(0, index));
-            this.text[key] = String.fromCharCode.apply(String, text.slice(index + 1));
+            var text = this.read(chunkSize);
+            var index = text.indexOf(0);
+            var key = String.fromCharCode.apply(String, text.slice(0, index));
+            this.text[key] = String.fromCharCode.apply(
+              String,
+              text.slice(index + 1)
+            );
             break;
+
           case 'IEND':
@@ -166,64 +192,69 @@ if (frame) {
             }
-            this.colors = (function() {
-              switch (this.colorType) {
-                case 0:
-                case 3:
-                case 4:
-                  return 1;
-                case 2:
-                case 6:
-                  return 3;
-              }
-            }).call(this);
-            this.hasAlphaChannel = (_ref = this.colorType) === 4 || _ref === 6;
-            colors = this.colors + (this.hasAlphaChannel ? 1 : 0);
+
+            // we've got everything we need!
+            switch (this.colorType) {
+              case 0:
+              case 3:
+              case 4:
+                this.colors = 1;
+                break;
+              case 2:
+              case 6:
+                this.colors = 3;
+                break;
+            }
+
+            this.hasAlphaChannel = [4, 6].includes(this.colorType);
+            var colors = this.colors + (this.hasAlphaChannel ? 1 : 0);
             this.pixelBitlength = this.bits * colors;
-            this.colorSpace = (function() {
-              switch (this.colors) {
-                case 1:
-                  return 'DeviceGray';
-                case 3:
-                  return 'DeviceRGB';
-              }
-            }).call(this);
+
+            switch (this.colors) {
+              case 1:
+                this.colorSpace = 'DeviceGray';
+                break;
+              case 3:
+                this.colorSpace = 'DeviceRGB';
+                break;
+            }
+
             this.imgData = new Uint8Array(this.imgData);
             return;
+            break;
+
           default:
+            // unknown (or unimportant) section, skip it
             this.pos += chunkSize;
         }
-        this.pos += 4;
+
+        this.pos += 4; // Skip the CRC
+
         if (this.pos > this.data.length) {
-          throw new Error("Incomplete or corrupt PNG file");
+          throw new Error('Incomplete or corrupt PNG file');
         }
       }
-      return;
     }
 
-    PNG.prototype.read = function(bytes) {
-      var i, _i, _results;
-      _results = [];
-      for (i = _i = 0; 0 <= bytes ? _i < bytes : _i > bytes; i = 0 <= bytes ? ++_i : --_i) {
-        _results.push(this.data[this.pos++]);
+    read(bytes) {
+      const result = new Array(bytes);
+      for (let i = 0; i < bytes; i++) {
+        result[i] = this.data[this.pos++];
       }
-      return _results;
-    };
+      return result;
+    }
 
-    PNG.prototype.readUInt32 = function() {
-      var b1, b2, b3, b4;
-      b1 = this.data[this.pos++] << 24;
-      b2 = this.data[this.pos++] << 16;
-      b3 = this.data[this.pos++] << 8;
-      b4 = this.data[this.pos++];
+    readUInt32() {
+      const b1 = this.data[this.pos++] << 24;
+      const b2 = this.data[this.pos++] << 16;
+      const b3 = this.data[this.pos++] << 8;
+      const b4 = this.data[this.pos++];
       return b1 | b2 | b3 | b4;
-    };
+    }
 
-    PNG.prototype.readUInt16 = function() {
-      var b1, b2;
-      b1 = this.data[this.pos++] << 8;
-      b2 = this.data[this.pos++];
+    readUInt16() {
+      const b1 = this.data[this.pos++] << 8;
+      const b2 = this.data[this.pos++];
       return b1 | b2;
-    };
+    }
 
-    PNG.prototype.decodePixels = function(data) {
-      var byte, c, col, i, left, length, p, pa, paeth, pb, pc, pixelBytes, pixels, pos, row, scanlineLength, upper, upperLeft, _i, _j, _k, _l, _m;
+    decodePixels(data) {
       if (data == null) {
@@ -235,110 +266,194 @@ data = this.imgData;
       }
+
       data = new FlateStream(data);
       data = data.getBytes();
-      pixelBytes = this.pixelBitlength / 8;
-      scanlineLength = pixelBytes * this.width;
-      pixels = new Uint8Array(scanlineLength * this.height);
-      length = data.length;
-      row = 0;
-      pos = 0;
-      c = 0;
-      while (pos < length) {
-        switch (data[pos++]) {
-          case 0:
-            for (i = _i = 0; _i < scanlineLength; i = _i += 1) {
-              pixels[c++] = data[pos++];
-            }
-            break;
-          case 1:
-            for (i = _j = 0; _j < scanlineLength; i = _j += 1) {
-              byte = data[pos++];
-              left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
-              pixels[c++] = (byte + left) % 256;
-            }
-            break;
-          case 2:
-            for (i = _k = 0; _k < scanlineLength; i = _k += 1) {
-              byte = data[pos++];
-              col = (i - (i % pixelBytes)) / pixelBytes;
-              upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
-              pixels[c++] = (upper + byte) % 256;
-            }
-            break;
-          case 3:
-            for (i = _l = 0; _l < scanlineLength; i = _l += 1) {
-              byte = data[pos++];
-              col = (i - (i % pixelBytes)) / pixelBytes;
-              left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
-              upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
-              pixels[c++] = (byte + Math.floor((left + upper) / 2)) % 256;
-            }
-            break;
-          case 4:
-            for (i = _m = 0; _m < scanlineLength; i = _m += 1) {
-              byte = data[pos++];
-              col = (i - (i % pixelBytes)) / pixelBytes;
-              left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
-              if (row === 0) {
-                upper = upperLeft = 0;
-              } else {
-                upper = pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
-                upperLeft = col && pixels[(row - 1) * scanlineLength + (col - 1) * pixelBytes + (i % pixelBytes)];
+
+      const { width, height } = this;
+      const pixelBytes = this.pixelBitlength / 8;
+
+      const pixels = new Uint8Array(width * height * pixelBytes);
+      const { length } = data;
+      let pos = 0;
+
+      function pass(x0, y0, dx, dy, singlePass = false) {
+        const w = Math.ceil((width - x0) / dx);
+        const h = Math.ceil((height - y0) / dy);
+        const scanlineLength = pixelBytes * w;
+        const buffer = singlePass ? pixels : new Uint8Array(scanlineLength * h);
+        let row = 0;
+        let c = 0;
+        while (row < h && pos < length) {
+          var byte, col, i, left, upper;
+          switch (data[pos++]) {
+            case 0: // None
+              for (i = 0; i < scanlineLength; i++) {
+                buffer[c++] = data[pos++];
               }
-              p = left + upper - upperLeft;
-              pa = Math.abs(p - left);
-              pb = Math.abs(p - upper);
-              pc = Math.abs(p - upperLeft);
-              if (pa <= pb && pa <= pc) {
-                paeth = left;
-              } else if (pb <= pc) {
-                paeth = upper;
-              } else {
-                paeth = upperLeft;
+              break;
+
+            case 1: // Sub
+              for (i = 0; i < scanlineLength; i++) {
+                byte = data[pos++];
+                left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
+                buffer[c++] = (byte + left) % 256;
               }
-              pixels[c++] = (byte + paeth) % 256;
+              break;
+
+            case 2: // Up
+              for (i = 0; i < scanlineLength; i++) {
+                byte = data[pos++];
+                col = (i - (i % pixelBytes)) / pixelBytes;
+                upper =
+                  row &&
+                  buffer[
+                    (row - 1) * scanlineLength +
+                      col * pixelBytes +
+                      (i % pixelBytes)
+                  ];
+                buffer[c++] = (upper + byte) % 256;
+              }
+              break;
+
+            case 3: // Average
+              for (i = 0; i < scanlineLength; i++) {
+                byte = data[pos++];
+                col = (i - (i % pixelBytes)) / pixelBytes;
+                left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
+                upper =
+                  row &&
+                  buffer[
+                    (row - 1) * scanlineLength +
+                      col * pixelBytes +
+                      (i % pixelBytes)
+                  ];
+                buffer[c++] = (byte + Math.floor((left + upper) / 2)) % 256;
+              }
+              break;
+
+            case 4: // Paeth
+              for (i = 0; i < scanlineLength; i++) {
+                var paeth, upperLeft;
+                byte = data[pos++];
+                col = (i - (i % pixelBytes)) / pixelBytes;
+                left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
+
+                if (row === 0) {
+                  upper = upperLeft = 0;
+                } else {
+                  upper =
+                    buffer[
+                      (row - 1) * scanlineLength +
+                        col * pixelBytes +
+                        (i % pixelBytes)
+                    ];
+                  upperLeft =
+                    col &&
+                    buffer[
+                      (row - 1) * scanlineLength +
+                        (col - 1) * pixelBytes +
+                        (i % pixelBytes)
+                    ];
+                }
+
+                const p = left + upper - upperLeft;
+                const pa = Math.abs(p - left);
+                const pb = Math.abs(p - upper);
+                const pc = Math.abs(p - upperLeft);
+
+                if (pa <= pb && pa <= pc) {
+                  paeth = left;
+                } else if (pb <= pc) {
+                  paeth = upper;
+                } else {
+                  paeth = upperLeft;
+                }
+
+                buffer[c++] = (byte + paeth) % 256;
+              }
+              break;
+
+            default:
+              throw new Error(`Invalid filter algorithm: ${data[pos - 1]}`);
+          }
+
+          if (!singlePass) {
+            let pixelsPos = ((y0 + row * dy) * width + x0) * pixelBytes;
+            let bufferPos = row * scanlineLength;
+            for (i = 0; i < w; i++) {
+              for (let j = 0; j < pixelBytes; j++)
+                pixels[pixelsPos++] = buffer[bufferPos++];
+              pixelsPos += (dx - 1) * pixelBytes;
             }
-            break;
-          default:
-            throw new Error("Invalid filter algorithm: " + data[pos - 1]);
+          }
+
+          row++;
         }
-        row++;
       }
+
+      if (this.interlaceMethod === 1) {
+        /*
+          1 6 4 6 2 6 4 6
+          7 7 7 7 7 7 7 7
+          5 6 5 6 5 6 5 6
+          7 7 7 7 7 7 7 7
+          3 6 4 6 3 6 4 6
+          7 7 7 7 7 7 7 7
+          5 6 5 6 5 6 5 6
+          7 7 7 7 7 7 7 7
+        */
+        pass(0, 0, 8, 8); // 1
+        pass(4, 0, 8, 8); // 2
+        pass(0, 4, 4, 8); // 3
+        pass(2, 0, 4, 4); // 4
+        pass(0, 2, 2, 4); // 5
+        pass(1, 0, 2, 2); // 6
+        pass(0, 1, 1, 2); // 7
+      } else {
+        pass(0, 0, 1, 1, true);
+      }
+
       return pixels;
-    };
+    }
 
-    PNG.prototype.decodePalette = function() {
-      var c, i, length, palette, pos, ret, transparency, _i, _ref, _ref1;
-      palette = this.palette;
-      transparency = this.transparency.indexed || [];
-      ret = new Uint8Array((transparency.length || 0) + palette.length);
-      pos = 0;
-      length = palette.length;
-      c = 0;
-      for (i = _i = 0, _ref = palette.length; _i < _ref; i = _i += 3) {
+    decodePalette() {
+      const { palette } = this;
+      const { length } = palette;
+      const transparency = this.transparency.indexed || [];
+      const ret = new Uint8Array((transparency.length || 0) + length);
+      let pos = 0;
+      let c = 0;
+
+      for (let i = 0; i < length; i += 3) {
+        var left;
         ret[pos++] = palette[i];
         ret[pos++] = palette[i + 1];
         ret[pos++] = palette[i + 2];
-        ret[pos++] = (_ref1 = transparency[c++]) != null ? _ref1 : 255;
+        ret[pos++] = (left = transparency[c++]) != null ? left : 255;
       }
+
       return ret;
-    };
+    }
 
-    PNG.prototype.copyToImageData = function(imageData, pixels) {
-      var alpha, colors, data, i, input, j, k, length, palette, v, _ref;
-      colors = this.colors;
-      palette = null;
-      alpha = this.hasAlphaChannel;
+    copyToImageData(imageData, pixels) {
+      let j, k;
+      let { colors } = this;
+      let palette = null;
+      let alpha = this.hasAlphaChannel;
+
       if (this.palette.length) {
-        palette = (_ref = this._decodedPalette) != null ? _ref : this._decodedPalette = this.decodePalette();
+        palette =
+          this._decodedPalette || (this._decodedPalette = this.decodePalette());
         colors = 4;
         alpha = true;
       }
-      data = imageData.data;
-      length = data.length;
-      input = palette || pixels;
-      i = j = 0;
+
+      const data = imageData.data || imageData;
+      const { length } = data;
+      const input = palette || pixels;
+      let i = (j = 0);
+
       if (colors === 1) {
         while (i < length) {
           k = palette ? pixels[i / 4] * 4 : j;
-          v = input[k++];
+          const v = input[k++];
           data[i++] = v;
@@ -360,93 +475,85 @@ data[i++] = v;
       }
-    };
+    }
 
-    PNG.prototype.decode = function() {
-      var ret;
-      ret = new Uint8Array(this.width * this.height * 4);
+    decode() {
+      const ret = new Uint8Array(this.width * this.height * 4);
       this.copyToImageData(ret, this.decodePixels());
       return ret;
-    };
+    }
 
-    scratchCanvas = document.createElement('canvas');
-
-    scratchCtx = scratchCanvas.getContext('2d');
-
-    makeImage = function(imageData) {
-      var img;
-      scratchCtx.width = imageData.width;
-      scratchCtx.height = imageData.height;
-      scratchCtx.clearRect(0, 0, imageData.width, imageData.height);
-      scratchCtx.putImageData(imageData, 0, 0);
-      img = new Image;
-      img.src = scratchCanvas.toDataURL();
-      return img;
-    };
-
-    PNG.prototype.decodeFrames = function(ctx) {
-      var frame, i, imageData, pixels, _i, _len, _ref, _results;
+    decodeFrames(ctx) {
       if (!this.animation) {
         return;
       }
-      _ref = this.animation.frames;
-      _results = [];
-      for (i = _i = 0, _len = _ref.length; _i < _len; i = ++_i) {
-        frame = _ref[i];
-        imageData = ctx.createImageData(frame.width, frame.height);
-        pixels = this.decodePixels(new Uint8Array(frame.data));
+
+      for (let i = 0; i < this.animation.frames.length; i++) {
+        const frame = this.animation.frames[i];
+        const imageData = ctx.createImageData(frame.width, frame.height);
+        const pixels = this.decodePixels(new Uint8Array(frame.data));
+
         this.copyToImageData(imageData, pixels);
         frame.imageData = imageData;
-        _results.push(frame.image = makeImage(imageData));
+        frame.image = makeImage(imageData);
       }
-      return _results;
-    };
+    }
 
-    PNG.prototype.renderFrame = function(ctx, number) {
-      var frame, frames, prev;
-      frames = this.animation.frames;
-      frame = frames[number];
-      prev = frames[number - 1];
+    renderFrame(ctx, number) {
+      const { frames } = this.animation;
+      const frame = frames[number];
+      const prev = frames[number - 1];
+
+      // if we're on the first frame, clear the canvas
       if (number === 0) {
         ctx.clearRect(0, 0, this.width, this.height);
       }
-      if ((prev != null ? prev.disposeOp : void 0) === APNG_DISPOSE_OP_BACKGROUND) {
+
+      // check the previous frame's dispose operation
+      if ((prev && prev.disposeOp) === APNG_DISPOSE_OP_BACKGROUND) {
         ctx.clearRect(prev.xOffset, prev.yOffset, prev.width, prev.height);
-      } else if ((prev != null ? prev.disposeOp : void 0) === APNG_DISPOSE_OP_PREVIOUS) {
+      } else if ((prev && prev.disposeOp) === APNG_DISPOSE_OP_PREVIOUS) {
         ctx.putImageData(prev.imageData, prev.xOffset, prev.yOffset);
       }
+
+      // APNG_BLEND_OP_SOURCE overwrites the previous data
       if (frame.blendOp === APNG_BLEND_OP_SOURCE) {
         ctx.clearRect(frame.xOffset, frame.yOffset, frame.width, frame.height);
       }
+
+      // draw the current frame
       return ctx.drawImage(frame.image, frame.xOffset, frame.yOffset);
-    };
+    }
 
-    PNG.prototype.animate = function(ctx) {
-      var doFrame, frameNumber, frames, numFrames, numPlays, _ref,
-        _this = this;
-      frameNumber = 0;
-      _ref = this.animation, numFrames = _ref.numFrames, frames = _ref.frames, numPlays = _ref.numPlays;
-      return (doFrame = function() {
-        var f, frame;
-        f = frameNumber++ % numFrames;
-        frame = frames[f];
-        _this.renderFrame(ctx, f);
+    animate(ctx) {
+      let frameNumber = 0;
+      const { numFrames, frames, numPlays } = this.animation;
+
+      const doFrame = () => {
+        const f = frameNumber++ % numFrames;
+        const frame = frames[f];
+        this.renderFrame(ctx, f);
+
         if (numFrames > 1 && frameNumber / numFrames < numPlays) {
-          return _this.animation._timeout = setTimeout(doFrame, frame.delay);
+          this.animation._timeout = setTimeout(doFrame, frame.delay);
         }
-      })();
-    };
+      };
 
-    PNG.prototype.stopAnimation = function() {
-      var _ref;
-      return clearTimeout((_ref = this.animation) != null ? _ref._timeout : void 0);
-    };
+      doFrame();
+    }
 
-    PNG.prototype.render = function(canvas) {
-      var ctx, data;
+    stopAnimation() {
+      return clearTimeout(this.animation && this.animation._timeout);
+    }
+
+    render(canvas) {
+      // if this canvas was displaying another image before,
+      // stop the animation on it
       if (canvas._png) {
         canvas._png.stopAnimation();
       }
+
       canvas._png = this;
       canvas.width = this.width;
       canvas.height = this.height;
-      ctx = canvas.getContext("2d");
+      const ctx = canvas.getContext('2d');
+
       if (this.animation) {
@@ -456,14 +563,9 @@ this.decodeFrames(ctx);
       } else {
-        data = ctx.createImageData(this.width, this.height);
+        const data = ctx.createImageData(this.width, this.height);
         this.copyToImageData(data, this.decodePixels());
         return ctx.putImageData(data, 0, 0);
       }
-    };
-
-    return PNG;
-
-  })();
-
-  window.PNG = PNG;
-
-}).call(this);
+    }
+  }
+  return PNG;
+})();

README.md

@@ -27,3 +27,3 @@ png.js
     PNG.decode('some.png', function(pixels) {
-        // pixels is a 1d array of decoded pixel data
+        // pixels is a 1d array (in rgba order) of decoded pixel data
     });
@@ -34,2 +34,2 @@
 yourself which passes your callback the decoded pixels as a buffer.  If you already have a buffer you want the pixels
-copied to, call `copyToImageData` with your buffer and the decoded pixels as returned from `decodePixels`.
+copied to, call `copyToImageData` with your buffer and the decoded pixels as returned from `decodePixels`.

zlib.js

@@ -33,3 +33,3 @@ /*
 
-var DecodeStream = (function() {
+window.DecodeStream = (function() {
   function constructor() {
@@ -125,3 +125,3 @@ this.pos = 0;
 
-var FlateStream = (function() {
+window.FlateStream = (function() {
   var codeLenCodeMap = new Uint32Array([
@@ -128,0 +128,0 @@ 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15

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increased by58.25%

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