imagejs

ImageJS

Read, manipulate and write Images

Due to a lack of pure JavaScript Image manipulation libraries available, I decided to implement one.

This is an early release supporting only jpeg files and only the simplest resize algorithm but there will be more to come.

Installation

npm install imagejs

New Features!

• Enhanced Resize
  • New Resize Algorithm: Bicubic Interpolation

Coming Soon

• Bicubic Interpolation
• Crop
• Pad

Contents

• Interface
  • Creating Bitmaps
  • Manipulating Bitmaps
    • Set Pixel
  • Reading Images
  • Writing Images
• Release History

Interface

var ImageJS = require("imagejs");

Creating Bitmaps

// Create a blank bitmap 320x200
var blankBitmap = new ImageJS.Bitmap({width: 320, height: 200});

// Copy a bitmap
var copy = new ImageJS.Bitmap(otherBitmap);

// Create a bitmap and attach to supplied data structure
var attachedBitmap = new ImageJS.Bitmap({
    width: 100,
    height: 100,
    data: new Buffer(4 * 100 * 100)
});

// Create an empty (null) bitmap, ready for reading from file or stream
var nullBitmap = new ImageJS.Bitmap();

Manipulating Bitmaps

// Set a pixel
// where: 0 <= x < width, 0 <= y < height, 0 <= a,r,g,b < 256
bitmap.setPixel(x,y, a,r,g,b);

// Create a new bitmap that is a negative of the original
var negative = bitmap.negative();

// Create a new bitmap resized from an original

// resize to 64x64 icon sized bitmap using nearest neighbor algorithm & stretch to fit
var thumbnail = bitmap.resize({
    width: 64, height: 64,
    algorithm: "nearestNeighbor"
});

// resize to 100x150 bitmap using bilinear interpolation and cropping to fit, gravity center
var thumbnail = bitmap.resize({
    width: 100, height: 150,
    algorithm: "bilinearInterpolation",
    fit: "crop",
    gravity: {x:0.5, y:0.5} // center - note: this is the default
});

// resize to 300x200 bitmap using bicubic interpolation and padding to fit, pad color solid red
var thumbnail = bitmap.resize({
    width: 300, height: 200,
    algorithm: "bicubicInterpolation",
    fit: "pad",
    padColor: {r:255, g:0, b:0, a:255}
});

Supported Resize Algorithms

• nearestNeighbor
• bilinearInterpolation
• bicubicInterpolation

Reading Images

// read from a file
var bitmap = new Bitmap();
bitmap.readFile(filename)
    .then(function() {
        // bitmap is ready
    });

// read JPG data from stream
var stream = createReadStream();
var bitmap = new Bitmap();
bitmap.read(stream, { type: ImageJS.ImageType.JPG })
    .then(function() {
        // bitmap is ready
    });

Writing Images

// write to a jpg file, quality 75 (default is 90)
return bitmap.writeFile("image.jpg", { quality:75 })
    .then(function() {
        // bitmap has been saved
    });

// write PNG Image to a stream
var stream = createWriteStream();
return bitmap.write(stream, {type: ImageJS.ImageType.PNG})
    .then(function() {
        // bitmap has been written and stream ended
    });

Release History

Version	Changes
0.0.1	Initial Version
0.0.2	Enhanced Resize New Resize Algorithm: Bilinear Interpolation Stretch, Crop or Pad to Fit PNG Image files supported
0.0.3	Enhanced Resize New Resize Algorithm: Bicubic Interpolation