Buffer creation from HTML image elements w/ opt resize & format conversion (browser only)
Buffer-to-buffer blitting w/ automatic format conversion
Buffer-to-canvas blitting
Buffer-to-buffer blending w/ Porter-Duff operators
Pre/post-multiply alpha
Region / sub-image extraction
Single-channel manipulation / extraction / replacement / conversion
k-means based dominant color extraction (float buffers only)
Accessors for normalized channel value
Image sampling, resizing, pooling
- Filters: nearest neighbor, bilinear, bicubic
- Wrap behaviors: clamp, wrap, repeat
- Pooling: mean/min/max
Invert image
Convolution w/ arbitrary shaped/sized kernels, pooling, striding
Convolution kernel & pooling kernels presets
- Higher order kernel generators (Gaussian, Lanczos)
Image pyramid generation (w/ customizable kernels)
Customizable normal map generation (i.e. X/Y gradients plus static Z component)
XY full pixel & channel-only accessors
12 packed integer and 6 floating point preset formats (see table below)
Declarative custom format & optimized code generation
HTML canvas creation & ImageData utilities

Integer pixel formats

All integer formats use the canvas native ABGR 32bit format as common intermediate for conversions. During conversion to ABGR, channels with sizes smaller than 8 bits will be scaled appropriately to ensure an as full-range and as linear as possible mapping. E.g. a 4 bit channel will be scaled by 255 / 15 = 17.

Format specs can freely control channel layout within current limits:

Channel sizes: 1 - 32 bits.
Storage: 8, 16 or 32 bits per pixel

New formats can be defined via defIntFormat().

Format ID	Bits per pixel	Description
`ALPHA8`	8	8 bit channel (alpha only)
`GRAY8`	8	8 bit single channel (grayscale conv)
`GRAY_ALPHA8`	16	8 bit single channel (grayscale conv), 8 bit alpha
`GRAY16`	16	16 bit single channel (grayscale conv)
`GRAY_ALPHA16`	32	16 bit single channel (grayscale conv), 16 bit alpha
`ARGB4444`	16	4 channels @ 4 bits each
`ARGB1555`	16	5 bits each for RGB, 1 bit alpha
`RGB565`	16	5 bits red, 6 bits green, 5 bits blue
`RGB888`	32 (24 effective)	3 channels @ 8 bits each
`ARGB8888`	32	4 channels @ 8 bits each
`BGR888`	32 (24 effective)	3 channels @ 8 bits each
`ABGR8888`	32	4 channels @ 8 bits each

ALPHA8 is mapped from/to ABGR alpha channel
GRAY8/16, GRAY_ALPHA8/16 compute grayscale/luminance when converting from ABGR and in return produce grayscale ABGR
In all built-in formats supporting it, the alpha channel always occupies the most-significant bits (up to format size)

Floating point pixel formats

Strided floating point format presets for use with floatBuffer(). New formats can be defined via defFloatFormat().

Format ID	Channel count	Description
`FLOAT_GRAY`	1	Single channel / grayscale
`FLOAT_GRAY_ALPHA`	2	Grayscale and alpha channel
`FLOAT_GRAY_RANGE`	1	Grayscale (user defined value range)
`FLOAT_NORMAL`	3	Normal map (signed values)
`FLOAT_RGB`	3	Red, Green, Blue
`FLOAT_RGBA`	4	Red, Green, Blue, Alpha

All color channels are unclamped (but can be clamped via buf.clamp()). For conversion to packed int formats assumed to contain normalized data (i.e. [0..1] interval, with exception of FLOAT_NORMAL which uses [-1..1] range)
Conversion between float formats is currently unsupported

Filtered image sampling and resizing

Available (and optimized) for both integer & floating point formats, image samplers can be created with the following filters & wrap modes:

Filters

"nearest" - nearest neighbor
"linear" - bilinear interpolation
"cubic" - bicubic interpolation

Wrap mode

"clamp" - outside values return 0
"wrap" - infinite tiling
"repeat" - edge pixels are repeated

const src = intBuffer(4, 4, ABGR8888);

// fill w/ random colors
src.forEach((_,i) => 0xff000000 | Math.random() * 0xffffff);

// create bilinear sampler w/ repeated edge pixels
const sampler = defSampler(src, "linear", "repeat");

// sample at fractional positions (even outside image)
sampler(-1.1, 0.5).toString(16)
// 'ff79643a'

// resize image to 1024x256 using bicubic sampling
const img = src.resize(1024, 256, "cubic");

Filter
`"nearest"`
`"linear"`
`"cubic"`

Strided convolution & pooling

Floating point buffers can be processed using arbitrary convolution kernels. The following convolution kernel presets are provided for convenience:

Kernel	Size
`BOX_BLUR3`	3x3
`BOX_BLUR5`	5x5
`GAUSSIAN_BLUR3`	3x3
`GAUSSIAN_BLUR5`	5x5
`GAUSSIAN(n)`	2n+1 x 2n+1
`HIGHPASS3`	3x3
`LANCZOS(a,s)`	as+1 x as+1
`SHARPEN3`	3x3
`SOBEL_X`	3x3
`SOBEL_Y`	3x3
`UNSHARP_MASK5`	5x5

Custom kernels can be defined (and code generated) using an array of coefficients and a given kernel size. See above presets and defKernel() for reference.

Furthermore, convolution supports striding (i.e. only processing & keeping every nth pixel column/row, aka downscaling) and pixel pooling (e.g. for ML applications). Available pooling kernel presets (kernel sizes must be configured independently):

Kernel	Description
`POOL_MEAN`	Moving average
`POOL_MAX`	Local maximum
`POOL_MIN`	Local minimum
`POOL_NEAREST`	Nearest neighbor
`POOL_THRESHOLD(bias)`	Adaptive threshold

Convolution can be applied to single, multiple or all channels of a FloatBuffer. See convolveChannel() and convolveImage().

See ConvolveOpts for config options.

// convolutions are only available for float buffers (for now)
src = floatBuffer(read("test.ppm"), FLOAT_RGB);

// apply horizontal Sobel kernel preset to all channels
// downscale image by factor 2 (must be integer)
// scale kernel result values by factor 4
convolveImage(src, { kernel: SOBEL_X, stride: 2, scale: 4 });

Normal map generation

Normal maps can be created via normalMap(). This function uses an adjustable convolution kernel size to control gradient smoothness & details. Result X/Y gradients can also be scaled (uniform or anisotropic) and the Z component can be customized to (default: 1.0). The resulting image is in FLOAT_NORMAL format, using signed channel values. This channel format is auto-translating these into unsigned values when the image is converted into an integer format.

Step	Scale = 1	Scale = 2	Scale = 4	Scale = 8
0
1
2
3

import { floatBuffer, normalMap, FLOAT_GRAY, RGB888 } from "@thi.ng/pixel";
import { asPPM, read } from "@thi.ng/pixel-io-netpbm";

// read source image into a single channel floating point buffer
const src = floatBuffer(read(readFileSync("noise.pgm")), FLOAT_GRAY);

// create normal map (w/ default options)
const nmap = normalMap(src, { step: 0, scale: 1 });

// pixel lookup (vectors are stored _un_normalized)
nmap.getAt(10, 10);
// Float32Array(3) [ -0.019607841968536377, -0.04313725233078003, 1 ]

// save as 24bit PBM, conversion to RGB int format first
writeFileSync("noise-normal.ppm", asPPM(nmap.as(RGB888)));

Dominant color extraction

The dominantColors() function applies k-means clustering to extract the dominant colors from the given image. The clustering can be configured. The function returns an array of { color, area } objects (sorted by descending area), where color is a cluster's dominant color (in the format of the source image) and area the normalized cluster size (number of selected pixels over total number of pixels in the image).

Also see the dominant colors example project & online tool based on this function. Furthermore, the thi.ng/color-palettes package provides 200+ curated color themes extracted from images using this function...

Picture credit: /u/kristophershinn

// read test PPM image and convert into float RGB format
const img = floatBuffer(read(readFileSync(`test.ppm`)), FLOAT_RGB);

// extract 5 dominant color clusters
const clusters = dominantColors(img, 5);

console.log(clusters);
// [
//   {
//     color: [ 0.4000000059604645, 0.30980393290519714, 0.21176470816135406 ],
//     area: 0.3141084558823529
//   },
//   {
//     color: [ 0.21960784494876862, 0.19607843458652496, 0.1411764770746231 ],
//     area: 0.2780330882352941
//   },
//   {
//     color: [ 0.4156862795352936, 0.4745098054409027, 0.5647059082984924 ],
//     area: 0.16620710784313725
//   },
//   {
//     color: [ 0.6666666865348816, 0.7568627595901489, 0.9254902005195618 ],
//     area: 0.12385110294117647
//   },
//   {
//     color: [ 0.7176470756530762, 0.4745098054409027, 0.12941177189350128 ],
//     area: 0.11780024509803921
//   }
// ]

Status

STABLE - used in production

Search or submit any issues for this package

Support packages

@thi.ng/pixel-dither - Extensible image dithering w/ various algorithm presets
@thi.ng/pixel-io-geotiff - GeoTIFF reader support for @thi.ng/pixel
@thi.ng/pixel-io-netpbm - Multi-format NetPBM reader & writer support for @thi.ng/pixel
@thi.ng/pixel-io-pfm - Portable FloatMap image format support for @thi.ng/pixel

@thi.ng/color - Array-based color types, CSS parsing, conversions, transformations, declarative theme generation, gradients, presets
@thi.ng/porter-duff - Porter-Duff operators for packed ints & float-array alpha compositing
@thi.ng/rasterize - 2D shape drawing & rasterization
@thi.ng/shader-ast - DSL to define shader code in TypeScript and cross-compile to GLSL, JS and other targets
@thi.ng/webgl - WebGL & GLSL abstraction layer

Installation

yarn add @thi.ng/pixel

ES module import:

<script type="module" src="https://cdn.skypack.dev/@thi.ng/pixel"></script>

Skypack documentation

For Node.js REPL:

const pixel = await import("@thi.ng/pixel");

Package sizes (brotli'd, pre-treeshake): ESM: 9.44 KB

Dependencies

Usage examples

Several projects in this repo's /examples directory are using this package:

Description	Live demo	Source
Interactive image processing (adaptive threshold)	Demo	Source
ASCII art raymarching with thi.ng/shader-ast & thi.ng/text-canvas	Demo	Source
Color palette generation via dominant color extraction from uploaded images	Demo	Source
2.5D hidden line visualization of digital elevation files (DEM)	Demo	Source
Barnsley fern IFS fractal renderer	Demo	Source
Pixel buffer manipulations	Demo	Source
Showcase of various dithering algorithms	Demo	Source
Randomized 4-point 2D color gradient image generator	Demo	Source
Image dithering and remapping using indexed palettes	Demo	Source
Normal map creation/conversion basics	Demo	Source
Interactive pixel sorting tool using thi.ng/color & thi.ng/pixel	Demo	Source
Port-Duff image compositing / alpha blending	Demo	Source
Steering behavior drawing with alpha-blended shapes	Demo	Source
Responsive image gallery with tag-based Jaccard similarity ranking	Demo	Source
2D scenegraph & image map based geometry manipulation	Demo	Source
WebGL & Canvas2D textured tunnel shader	Demo	Source
Fork-join worker-based raymarch renderer (JS/CPU only)	Demo	Source
Textmode image warping w/ 16bit color output	Demo	Source
Multi-layer vectorization & dithering of bitmap images	Demo	Source
Visual comparison of biased vs. unbiased normal vectors projected on the surface of a sphere	Demo	Source
Minimal multi-pass / GPGPU example	Demo	Source

API

Generated API docs

import * as pix from "@thi.ng/pixel";
import { SRC_OVER_I } from "@thi.ng/porter-duff";

import IMG from "../assets/haystack.jpg";
import LOGO from "../assets/logo-64.png";

Promise
    .all([IMG, LOGO].map(pix.imagePromise))
    .then(([img, logo]) => {

        // init 16 bit packed RGB pixel buffer from image (resized to 256x256)
        const buf = intBufferFromImage(img, pix.RGB565, 256, 256);

        // create grayscale buffer for logo and use Porter-Duff operator to
        // composite with main image. Since the logo has transparency, we need
        // to premultiply alpha first...
        pix.intBufferFromImage(logo, pix.GRAY_ALPHA88)
            .premultiply()
            .blend(SRC_OVER_I, buf, {
                dx: 10,
                dy: 10
            });

        // extract sub-image
        const region = buf.getRegion(32, 96, 128, 64);
        // copy region back at new position
        region.blit(buf, { dx: 96, dy: 32 });

        // or alternatively blit buf into itself
        // buf.blit(buf, { dx: 96, dy: 32, sx: 32, sy: 96, w: 128, h: 64 });

        // create html canvas
        // (returns obj of canvas & 2d context)
        const ctx = pix.canvas2d(buf.width, buf.height * 3, document.body);

        // write pixel buffer to canvas
        buf.blitCanvas(ctx.canvas);

        // manipulate single color channel (here red)
        const id = 0;
        // obtain channel & invert
        const ch = buf.getChannel(id).invert();
        // create dot pattern
        for (let y = 0; y < ch.height; y += 2) {
            for (let x = (y >> 1) & 1; x < ch.width; x += 2) {
                ch.setAt(x, y, 0xff);
            }
        }
        // replace original channel
        buf.setChannel(id, ch);

        // write pixel buffer to new position
        buf.blitCanvas(ctx.canvas, { y: buf.height });

        // create & write grayscale version
        buf.as(GRAY8).blitCanvas(ctx.canvas, { y: buf.height * 2 });
});

TODO see examples & source comments for now

Authors

Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-pixel,
  title = "@thi.ng/pixel",
  author = "Karsten Schmidt",
  note = "https://thi.ng/pixel",
  year = 2019
}

License

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Package last updated on 09 Nov 2023

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@thi.ng/pixel

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