ndarray-pixels v4.0.0
ndarray-pixels
Convert ndarray ↔ image data, on Web and Node.js.
Designed to be used with other ndarray-based packages.
Supported Formats
Platform | JPEG | PNG | Other |
---|---|---|---|
Node.js | ✅ | ✅ | Based on sharp support |
Web | ✅ | ✅ | Based on browser support |
Known Bugs
- Web implementation (Canvas 2D) premultiplies alpha.
Quickstart
npm install --save ndarray-pixels
Web
import { getPixels, savePixels } from 'ndarray-pixels';
const bytesIn = await fetch('./input.png')
.then((res) => res.arrayBuffer())
.then((arrayBuffer) => new Uint8Array(arrayBuffer));
// read
const pixels = await getPixels(bytesIn, 'image/png'); // Uint8Array -> ndarray
// modify
const [width, height] = pixels.shape;
for (let x = 0; x < width; ++x) {
for (let y = 0; y < height; ++y) {
pixels.set(x, y, 0, 255); // R
pixels.set(x, y, 1, 0.0); // G
pixels.set(x, y, 2, 0.0); // B
pixels.set(x, y, 3, 255); // A
}
}
// write
const bytesOut = await savePixels(pixels, 'image/png'); // ndarray -> Uint8Array
Node.js
const fs = require('fs');
const { getPixels, savePixels } = require('ndarray-pixels');
const bufferIn = fs.readFileSync('./input.png');
// read
const pixels = await getPixels(bufferIn, 'image/png'); // Uint8Array -> ndarray
// modify
const [width, height] = pixels.shape;
for (let x = 0; x < width; ++x) {
for (let y = 0; y < height; ++y) {
pixels.set(x, y, 0, 255); // R
pixels.set(x, y, 1, 0.0); // G
pixels.set(x, y, 2, 0.0); // B
pixels.set(x, y, 3, 255); // A
}
}
// write
const bufferOut = await savePixels(pixels, 'image/png'); // ndarray -> Uint8Array
fs.writeFileSync('./output.png', bufferOut);
API
getPixels
▸ getPixels(data
, mimeType
): Promise
\<NdArray
\<Uint8Array
>>
Decodes image data to an ndarray
.
MIME type is optional when given a path or URL, and required when given a Uint8Array.
Accepts image/png
or image/jpeg
in Node.js, and additional formats on browsers with
the necessary support in Canvas 2D.
Parameters
Name | Type | Description |
---|---|---|
data | Uint8Array | |
mimeType | string | image/jpeg , image/png , etc. |
Returns
Promise
\<NdArray
\<Uint8Array
>>
Defined in
savePixels
▸ savePixels(pixels
, mimeType
): Promise
\<Uint8Array
>
Encodes an ndarray
as image data in the given format.
If the source ndarray
was constructed manually with default stride, use
ndarray.transpose(1, 0)
to reshape it and ensure an identical result from getPixels(). For an
ndarray created by getPixels(), this isn't necessary.
Accepts image/png
or image/jpeg
in Node.js, and additional formats on browsers with
the necessary support in Canvas 2D.
Parameters
Name | Type | Description |
---|---|---|
pixels | NdArray \<Uint8Array | Uint8ClampedArray > | ndarray of shape W x H x 4. |
mimeType | string | image/jpeg , image/png , etc. |
Returns
Promise
\<Uint8Array
>
Defined in
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