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https://github.com/arian/pngjs
Pure JavaScript PNG decoder
https://github.com/arian/pngjs
Last synced: 14 days ago
JSON representation
Pure JavaScript PNG decoder
- Host: GitHub
- URL: https://github.com/arian/pngjs
- Owner: arian
- License: mit
- Created: 2012-07-09T00:36:51.000Z (over 12 years ago)
- Default Branch: master
- Last Pushed: 2021-02-13T09:00:26.000Z (over 3 years ago)
- Last Synced: 2024-10-15T04:07:12.610Z (30 days ago)
- Language: JavaScript
- Homepage:
- Size: 595 KB
- Stars: 180
- Watchers: 3
- Forks: 57
- Open Issues: 13
-
Metadata Files:
- Readme: README.md
- License: LICENSE.md
Awesome Lists containing this project
README
PNG.js
======
PNG.js is a PNG decoder fully written in JavaScript. It works in Node.js as
well as in (modern) browsers.
Usage
-----
``` js
var PNGReader = require('png.js');
var reader = new PNGReader(bytes);
reader.parse(function(err, png){
if (err) throw err;
console.log(png);
});
```
Or with options:
``` js
reader.parse({
data: false
}, function(err, png){
if (err) throw err;
console.log(png);
});
```
Currently the only option is:
- `data` (*boolean*) - should it read the pixel data, or only the image information.
### PNG object
The PNG object is passed in the callback. It contains all the data extracted
from the image.
``` js
// most importantly
png.getWidth();
png.getHeight();
png.getPixel(x, y); // [red, blue, green, alpha]
png.getRGBA8Array(); // [r1, g1, b1, a1, r2, b2, g2, a2, ... ] - Same as canvas.getImageData
// but also
png.getBitDepth();
png.getColorType();
png.getCompressionMethod();
png.getFilterMethod();
png.getInterlaceMethod();
png.getPalette();
```
Using PNGReader in Node.js
--------------------------
PNGReader accepts an `Buffer` object, returned by `fs.readFile`, for example:
``` js
fs.readFile('test.png', function(err, buffer){
var reader = new PNGReader(buffer);
reader.parse(function(err, png){
if (err) throw err;
console.log(png);
});
});
```
Using PNGReader in the Browser
------------------------------
PNGReader accepts a byte string, array of bytes or an ArrayBuffer.
For example using FileReader with file input fields:
```js
var reader = new FileReader();
reader.onload = function(event){
var reader = new PNGReader(event.target.result);
reader.parse(function(err, png){
if (err) throw err;
console.log(png);
});
};
fileInputElement.onchange = function(){
reader.readAsArrayBuffer(fileInputElement.files[0]);
// or, but less optimal
reader.readAsBinaryString(fileInputElement.files[0]);
};
```
Or instead of using input elements, XHR can also be used:
```js
var xhr = new XMLHttpRequest();
xhr.open('GET', 'image.png', true);
xhr.responseType = 'arraybuffer';
xhr.onload = function(e){
if (this.status == 200){
var reader = new PNGReader(this.response);
reader.parse(function(err, png){
if (err) throw err;
console.log(png);
});
}
};
xhr.send();
```
Building Browser Version
------------------------
PNG.js uses CommonJS modules which can be used in browsers after building it
with [browserify](http://browserify.org/):
browserify ./PNGReader.js -s PNGReader