About
========
Simple PNG encoder/decoder for Node.js with no native dependencies.
Installation
===============
``
$ npm install pngjs
Example
==========
`js
var fs = require('fs'),
PNG = require('pngjs').PNG;
fs.createReadStream('in.png')
.pipe(new PNG({
filterType: 4
}))
.on('parsed', function() {
for (var y = 0; y < this.height; y++) {
for (var x = 0; x < this.width; x++) {
var idx = (this.width * y + x) << 2;
// invert color
this.data[idx] = 255 - this.data[idx];
this.data[idx+1] = 255 - this.data[idx+1];
this.data[idx+2] = 255 - this.data[idx+2];
// and reduce opacity
this.data[idx+3] = this.data[idx+3] >> 1;
}
}
this.pack().pipe(fs.createWriteStream('out.png'));
});
`
For more examples see folder.
Documentation
================
As input any color type is accepted (grayscale, rgb, palette, grayscale with alpha, rgb with alpha) but 8 bit per sample (channel) is the only supported bit depth. Interlaced mode is not supported.
- gamma,
- tRNS - transparency (but only for paletted image)
Class: PNG
PNG is readable and writable Stream.
$3
- width - use this with height if you want to create png from scratch
- height - as above
- checkCRC - whether parser should be strict about checksums in source stream (default: true)
- deflateChunkSize - chunk size used for deflating data chunks, this should be power of 2 and must not be less than 256 and more than 32*1024 (default: 32 kB)
- deflateLevel - compression level for delate (default: 9)
- deflateStrategy - compression strategy for delate (default: 3)
- filterType - png filtering method for scanlines (default: -1 => auto, accepts array of numbers 0-4)
$3
function(metadata) { }
Image's header has been parsed, metadata contains this information:
- image size in pixels
- height image size in pixels
- palette image is paletted
- color image is not grayscale
- alpha image contains alpha channel
$3
function(data) { }
Input image has been completly parsed, is complete and ready for modification.
$3
function(error) { }
$3
Parses PNG file data. Alternatively you can stream data to instance of PNG.Optional
is once called on error or parsed. The callback gets
two arguments (err, data).Returns
this for method chaining.
$3
Starts converting data to PNG file Stream.Returns
this for method chaining.
$3
Helper for image manipulation, copies rectangle of pixels from current image (sx, sy, w, h) to dst image (at dx, dy).Returns
this` for method chaining.Changelog
============
License
=========
(The MIT License)
Copyright (c) 2012 Kuba Niegowski
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.