@thi.ng/pixel-convolve
v1.1.23TypeScript
Extensible bitmap image convolution, kernel presets, normal map & image pyramid generation
155/weekUpdated 2 days agoApache-2.0Unpacked: 47.1 KB
Published by Karsten Schmidt
npm install @thi.ng/pixel-convolve!@thi.ng/pixel-convolve
!npm downloads
> [!NOTE]
> This is one of 214 standalone projects, maintained as part
> of the @thi.ng/umbrella monorepo
> and anti-framework.
>
> 🚀 Please help me to work full-time on these projects by sponsoring me on
> GitHub. Thank you! ❤️
- About
- Strided convolution & pooling
- Normal map generation
- Status
- Installation
- Dependencies
- Usage examples
- API
- Authors
- License
About
Extensible bitmap image convolution, kernel presets, normal map & image pyramid generation. This is a support package for @thi.ng/pixel.
This package contains functionality which was previously part of and has been
extracted from the @thi.ng/pixel package.
- Convolution w/ arbitrary shaped/sized kernels, pooling, striding
- Convolution kernel & pooling kernels presets
- Higher order kernel generators (Gaussian, Lanczos)
- Image pooling filters (min/max, mean, adaptive threshold, custom)
- Image pyramid generation (w/ customizable kernels)
- Customizable normal map generation (i.e. X/Y gradients plus static Z component)
$3
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 |
| EDGE3 | 3x3 |
| EDGE5 | 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 anddefKernel() 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 aFloatBuffer. SeeconvolveChannel()
andconvolveImage().
See
ConvolveOpts
for config options.
``js tangle:export/readme-convolve.ts
import { floatBufferFromImage, FLOAT_RGB, imageFromURL } from "@thi.ng/pixel";
import { convolveImage, SOBEL_X } from "@thi.ng/pixel-convolve";
// convolutions are only available for float buffers (for now)
const src = floatBufferFromImage(await imageFromURL("test.jpg"), 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
const dest = convolveImage(src, { kernel: SOBEL_X, stride: 2, scale: 4 });
`
$3
Normal maps can be created via normalMap(). This function uses an adjustableFLOAT_NORMAL
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 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 |  |  |  |  |
`ts tangle:export/readme-normalmap.ts
import { ARGB8888, FLOAT_GRAY, floatBufferFromImage, imageFromURL } from "@thi.ng/pixel";
import { normalMap } from "@thi.ng/pixel-convolve";
// read source image into a single channel floating point buffer
const src = floatBufferFromImage(await imageFromURL("noise.png"), FLOAT_GRAY);
// create normal map (w/ default options)
// this results in a new float pixel buffer with FLOAT_RGB format
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 ]
// convert to 32bit packed int format
const nmapARGB = nmap.as(ARGB8888);
`
Status
STABLE - used in production
Search or submit any issues for this package
Installation
`bash`
yarn add @thi.ng/pixel-convolve
ESM import:
`ts`
import * as pc from "@thi.ng/pixel-convolve";
Browser ESM import:
`html`
For Node.js REPL:
`js`
const pc = await import("@thi.ng/pixel-convolve");
Package sizes (brotli'd, pre-treeshake): ESM: 2.29 KB
Dependencies
- @thi.ng/api
- @thi.ng/checks
- @thi.ng/errors
- @thi.ng/math
- @thi.ng/pixel
Note: @thi.ng/api is in _most_ cases a type-only import (not used at runtime)
Usage examples
Three projects in this repo's
/examples
directory are using this package:
| Screenshot | Description | Live demo | Source |
|:--------------------------------------------------------------------------------------------------------------------------|:----------------------------------------------------------------|:---------------------------------------------------------|:--------------------------------------------------------------------------------------|
| 
| Interactive image processing (adaptive threshold) | Demo | Source |
| 
| 2.5D hidden line visualization of digital elevation files (DEM) | Demo | Source |
| 
| Normal map creation/conversion basics | Demo | Source |
API
Authors
If this project contributes to an academic publication, please cite it as:
`bibtex``
@misc{thing-pixel-convolve,
title = "@thi.ng/pixel-convolve",
author = "Karsten Schmidt",
note = "https://thi.ng/pixel-convolve",
year = 2021
}
License
© 2021 - 2026 Karsten Schmidt // Apache License 2.0