javaScript实现基于Cesium，解析GFS数据实现的Windy粒子效果+源码+项目文档+demo（毕业设计&课程设计）

[](https://travis-ci.com/lukeapage/pngjs) [](https://ci.appveyor.com/project/lukeapage/pngjs/branch/master) [](https://codecov.io/gh/lukeapage/pngjs) [](http://badge.fury.io/js/pngjs) # pngjs Simple PNG encoder/decoder for Node.js with no dependencies. Based on the original [pngjs](https://github.com/niegowski/node-pngjs) with the follow enhancements. - Support for reading 1,2,4 & 16 bit files - Support for reading interlace files - Support for reading `tTRNS` transparent colours - Support for writing colortype 0 (grayscale), colortype 2 (RGB), colortype 4 (grayscale alpha) and colortype 6 (RGBA) - Sync interface as well as async - API compatible with pngjs and node-pngjs Known lack of support for: - Extended PNG e.g. Animation - Writing in colortype 3 (indexed color) # Table of Contents - [Requirements](#requirements) - [Comparison Table](#comparison-table) - [Tests](#tests) - [Installation](#installation) - [Browser](#browser) - [Example](#example) - [Async API](#async-api) - [Sync API](#sync-api) - [Changelog](#changelog) # Comparison Table | Name | Forked From | Sync | Async | 16 Bit | 1/2/4 Bit | Interlace | Gamma | Encodes | Tested | | ------------- | ----------- | ---- | ----- | ------ | --------- | --------- | ------ | ------- | ------ | | pngjs | | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | | node-png | pngjs | No | Yes | No | No | No | Hidden | Yes | Manual | | png-coder | pngjs | No | Yes | Yes | No | No | Hidden | Yes | Manual | | pngparse | | No | Yes | No | Yes | No | No | No | Yes | | pngparse-sync | pngparse | Yes | No | No | Yes | No | No | No | Yes | | png-async | | No | Yes | No | No | No | No | Yes | Yes | | png-js | | No | Yes | No | No | No | No | No | No | Native C++ node decoders: - png - png-sync (sync version of above) - pixel-png - png-img # Tests Tested using [PNG Suite](http://www.schaik.com/pngsuite/). We read every file into pngjs, output it in standard 8bit colour, synchronously and asynchronously, then compare the original with the newly saved images. To run the tests, fetch the repo (tests are not distributed via npm) and install with `npm i`, run `npm test`. The only thing not converted is gamma correction - this is because multiple vendors will do gamma correction differently, so the tests will have different results on different browsers. # Installation ``` $ npm install pngjs --save ``` # Browser The package has been build with a [Browserify](browserify.org) version (`npm run browserify`) and you can use the browser version by including in your code: ``` import { PNG } from 'pngjs/browser'; ``` # 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 `examples` folder. # Async API 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. ## Class: PNG `PNG` is readable and writable `Stream`. ### Options - `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 deflate (default: 9) - `deflateStrategy` - compression strategy for deflate (default: 3) - `deflateFactory` - deflate stream factory (default: `zlib.createDeflate`) - `filterType` - png filtering method for scanlines (default: -1 => auto, accepts array of numbers 0-4) - `colorType` - the output colorType - see constants. 0 = grayscale, no alpha, 2 = color, no alpha, 4 = grayscale & alpha, 6 = color & alpha. Default currently 6, but in the future may calculate best mode. - `inputColorType` - the input colorType - see constants. Default is 6 (RGBA) - `bitDepth` - the bitDepth of the output, 8 or 16 bits. Input data is expected to have this bit depth. 16 bit data is expected in the system endianness (Default: 8) - `inputHasAlpha` - whether the input bitmap has 4 bytes per pixel (rgb and alpha) or 3 (rgb - no alpha). - `bgColor` - an object containing red, green, and blue values between 0 and 255 that is used when packing a PNG if alpha is not to be included (default: 255,255,255) ### Event "metadata" `function(metadata) { }` Image's header has been parsed, metadata contains this information: - `width` image size in pixels - `height` image size in pixels - `palette` image is paletted - `color` image is not grayscale - `alpha` image contains alpha channel - `interlace` image is interlaced ### Event: "parsed" `function(data) { }` Input image has been completely parsed, `data` is complete and ready for modification. ### Event: "error" `function(error) { }` ### png.parse(data, [callback]) Parses PNG file data. Can be `String` or `Buffer`. Alternatively you can stream data to instance of PNG. Optional `callback` is once called on `error` or `parsed`. The callback gets two arguments `(err, data)`. Returns `this` for method chaining. #### Example ```js new PNG({ filterType: 4 }).parse(imageData, function (error, data) { console.log(error, data); }); ``` ### png.pack() Starts converting data to PNG file Stream. Returns `this` for method chaining. ### png.bitblt(dst, sx, sy, w, h, dx, dy) Helper for image manipulation, copies a rectangle of pixels from current (i.e. the source) image (`sx`, `sy`, `w`, `h`) to `dst` image (at `dx`, `dy`). Returns `this` for method chaining. For example, the following code copies the top-left 100x50 px of `in.png` into dst and writes it to `out.png`: ```js var dst = new PNG({ width: 100, height: 50 }); fs.createReadStream("in.png") .pipe(new PNG()) .on("parsed", function () { this.bitblt(dst, 0, 0, 100, 50, 0, 0); dst.pack().pipe(fs.createWriteStream("out.png")); }); ``` ### Property: adjustGamma() Helper that takes data and adjusts it to be gamma corrected. Note that it is not 100% reliable with transparent colours because that requires knowing the background colour the bitmap is rendered on to. In tests against PNG suite it compared 100% with chrome on all 8 bit and below images. On IE there were some differences. The following example reads a file, adjusts the gamma (which sets the gamma to 0) and writes it out again, effectively removing any gamma correction from the image. ```js fs.createReadStream("in.png") .pipe(new PNG()) .on("parsed", function () { this.adjustGamma(); this.pack().pipe(fs.createWriteStream("out.png")); }); ``` ### Property: width Width of image in pixels ### Property: height Height of image in pixels ### Property: da