mirror of
https://github.com/danbulant/pngjs
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156 lines
4.4 KiB
Markdown
156 lines
4.4 KiB
Markdown
About
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========
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Simple PNG encoder/decoder for Node.js with no native dependencies.
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Installation
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===============
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```
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$ npm install pngjs
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```
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Example
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==========
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```js
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var fs = require('fs'),
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PNG = require('pngjs').PNG;
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fs.createReadStream('in.png')
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.pipe(new PNG({
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filterType: 4
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}))
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.on('parsed', function() {
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for (var y = 0; y < this.height; y++) {
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for (var x = 0; x < this.width; x++) {
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var idx = (this.width * y + x) << 2;
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// invert color
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this.data[idx] = 255 - this.data[idx];
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this.data[idx+1] = 255 - this.data[idx+1];
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this.data[idx+2] = 255 - this.data[idx+2];
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// and reduce opacity
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this.data[idx+3] = this.data[idx+3] >> 1;
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}
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}
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this.pack().pipe(fs.createWriteStream('out.png'));
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});
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```
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For more examples see `examples` folder.
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Documentation
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================
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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.
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### Supported ancillary chunks
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- `gAMA` - gamma,
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- `tRNS` - transparency (but only for paletted image)
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## Class: PNG
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`PNG` is readable and writable `Stream`.
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### Options
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- `width` - use this with `height` if you want to create png from scratch
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- `height` - as above
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- `checkCRC` - whether parser should be strict about checksums in source stream (default: `true`)
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- `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)
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- `deflateLevel` - compression level for delate (default: 9)
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- `filterType` - png filtering method for scanlines (default: -1 => auto)
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### Event "metadata"
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`function(metadata) { }`
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Image's header has been parsed, metadata contains this information:
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- `width` image size in pixels
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- `height` image size in pixels
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- `palette` image is paletted
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- `color` image is not grayscale
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- `alpha` image contains alpha channel
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### Event: "parsed"
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`function(data) { }`
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Input image has been completly parsed, `data` is complete and ready for modification.
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### Event: "error"
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`function(error) { }`
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### png.parse(data, [callback])
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Parses PNG file data. Alternatively you can stream data to instance of PNG.
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Optional `callback` is once called on `error` or `parsed`. The callback gets
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two arguments `(err, data)`.
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Returns `this` for method chaining.
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### png.pack()
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Starts converting data to PNG file Stream.
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Returns `this` for method chaining.
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### png.bitblt(dst, sx, sy, w, h, dx, dy)
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Helper for image manipulation, copies rectangle of pixels from current image (`sx`, `sy`, `w`, `h`) to `dst` image (at `dx`, `dy`).
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Returns `this` for method chaining.
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### Property: width
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Width of image in pixels
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### Property: height
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Height of image in pixels
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### Property: data
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Buffer of image pixel data. Every pixel consists 4 bytes: R, G, B, A (opacity).
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### Property: gamma
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Gamma of image (0 if not specified)
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Changelog
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============
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### 0.3.0-alpha - 23 Aug 2012
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- Processing data as Streams, not complete Buffers of data
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### 0.2.0-alpha - 21 Aug 2012
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- Input added palette, grayscale, no alpha support
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- Better scanline filter selection
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### 0.1.0-alpha - 19 Aug 2012
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- First version
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License
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=========
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(The MIT License)
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Copyright (c) 2012 Kuba Niegowski
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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