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561 lines
14 KiB
JavaScript
561 lines
14 KiB
JavaScript
/**
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* This class lets you encode animated GIF files
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* Base class : http://www.java2s.com/Code/Java/2D-Graphics-GUI/AnimatedGifEncoder.htm
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* @author Kevin Weiner (original Java version - kweiner@fmsware.com)
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* @author Thibault Imbert (AS3 version - bytearray.org)
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* @author Kevin Kwok (JavaScript version - https://github.com/antimatter15/jsgif)
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* @version 0.1 AS3 implementation
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*/
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GIFEncoder = function() {
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for (var i = 0, chr = {}; i < 256; i++)
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chr[i] = String.fromCharCode(i);
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function ByteArray() {
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this.bin = [];
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}
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ByteArray.prototype.getData = function() {
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for (var v = '', l = this.bin.length, i = 0; i < l; i++)
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v += chr[this.bin[i]];
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return v;
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};
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ByteArray.prototype.writeByte = function(val) {
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this.bin.push(val);
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};
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ByteArray.prototype.writeUTFBytes = function(string) {
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for (var l = string.length, i = 0; i < l; i++)
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this.writeByte(string.charCodeAt(i));
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};
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ByteArray.prototype.writeBytes = function(array, offset, length) {
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for (var l = length || array.length, i = offset || 0; i < l; i++)
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this.writeByte(array[i]);
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};
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var exports = {};
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var width; // image size
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var height;
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var transparent = null; // transparent color if given
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var transIndex; // transparent index in color table
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var repeat = -1; // no repeat
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var delay = 0; // frame delay (hundredths)
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var started = false; // ready to output frames
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var out;
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var image; // current frame
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var pixels; // BGR byte array from frame
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var indexedPixels; // converted frame indexed to palette
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var colorDepth; // number of bit planes
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var colorTab; // RGB palette
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var usedEntry = []; // active palette entries
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var palSize = 7; // color table size (bits-1)
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var dispose = -1; // disposal code (-1 = use default)
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var closeStream = false; // close stream when finished
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var firstFrame = true;
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var sizeSet = false; // if false, get size from first frame
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var sample = 10; // default sample interval for quantizer
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var comment = "Generated by jsgif (https://github.com/antimatter15/jsgif/)"; // default comment for generated gif
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/**
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* Sets the delay time between each frame, or changes it for subsequent frames
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* (applies to last frame added)
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* int delay time in milliseconds
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* @param ms
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*/
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var setDelay = exports.setDelay = function setDelay(ms) {
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delay = Math.round(ms / 10);
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};
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/**
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* Sets the GIF frame disposal code for the last added frame and any
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*
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* subsequent frames. Default is 0 if no transparent color has been set,
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* otherwise 2.
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* @param code
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* int disposal code.
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*/
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var setDispose = exports.setDispose = function setDispose(code) {
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if (code >= 0) dispose = code;
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};
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/**
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* Sets the number of times the set of GIF frames should be played. Default is
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* 1; 0 means play indefinitely. Must be invoked before the first image is
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* added.
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*
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* @param iter
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* int number of iterations.
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* @return
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*/
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var setRepeat = exports.setRepeat = function setRepeat(iter) {
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if (iter >= 0) repeat = iter;
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};
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/**
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* Sets the transparent color for the last added frame and any subsequent
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* frames. Since all colors are subject to modification in the quantization
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* process, the color in the final palette for each frame closest to the given
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* color becomes the transparent color for that frame. May be set to null to
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* indicate no transparent color.
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* @param
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* Color to be treated as transparent on display.
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*/
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var setTransparent = exports.setTransparent = function setTransparent(c) {
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transparent = c;
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};
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/**
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* Sets the comment for the block comment
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* @param
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* string to be insterted as comment
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*/
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var setComment = exports.setComment = function setComment(c) {
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comment = c;
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};
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/**
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* The addFrame method takes an incoming BitmapData object to create each frames
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* @param
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* BitmapData object to be treated as a GIF's frame
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*/
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var addFrame = exports.addFrame = function addFrame(im, is_imageData) {
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if ((im === null) || !started || out === null) {
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throw new Error("Please call start method before calling addFrame");
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}
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var ok = true;
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try {
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if (!is_imageData) {
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image = im.getImageData(0, 0, im.canvas.width, im.canvas.height).data;
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if (!sizeSet) setSize(im.canvas.width, im.canvas.height);
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} else {
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if(im instanceof ImageData) {
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image = im.data;
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if(!sizeset || width!=im.width || height!=im.height) {
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setSize(im.width,im.height);
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} else {
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}
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} else if(im instanceof Uint8ClampedArray) {
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if(im.length==(width*height*4)) {
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image=im;
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} else {
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console.log("Please set the correct size: ImageData length mismatch");
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ok=false;
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}
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} else {
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console.log("Please provide correct input");
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ok=false;
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}
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}
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getImagePixels(); // convert to correct format if necessary
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analyzePixels(); // build color table & map pixels
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if (firstFrame) {
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writeLSD(); // logical screen descriptior
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writePalette(); // global color table
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if (repeat >= 0) {
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// use NS app extension to indicate reps
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writeNetscapeExt();
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}
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}
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writeGraphicCtrlExt(); // write graphic control extension
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if (comment !== '') {
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writeCommentExt(); // write comment extension
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}
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writeImageDesc(); // image descriptor
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if (!firstFrame) writePalette(); // local color table
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writePixels(); // encode and write pixel data
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firstFrame = false;
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} catch (e) {
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ok = false;
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}
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return ok;
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};
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/**
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* @description: Downloads the encoded gif with the given name
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* No need of any conversion from the stream data (out) to base64
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* Solves the issue of large file sizes when there are more frames
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* and does not involve in creation of any temporary data in the process
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* so no wastage of memory, and speeds up the process of downloading
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* to just calling this function.
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* @parameter {String} filename filename used for downloading the gif
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*/
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var download = exports.download = function download(filename) {
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if(out===null || closeStream==false) {
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console.log("Please call start method and add frames and call finish method before calling download");
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} else {
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filename= filename !== undefined ? ( filename.endsWith(".gif")? filename: filename+".gif" ): "download.gif";
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var templink = document.createElement("a");
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templink.download=filename;
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templink.href= URL.createObjectURL(new Blob([new Uint8Array(out.bin)], {type : "image/gif" } ));
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templink.click();
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}
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}
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/**
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* Adds final trailer to the GIF stream, if you don't call the finish method
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* the GIF stream will not be valid.
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*/
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var finish = exports.finish = function finish() {
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if (!started) return false;
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var ok = true;
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started = false;
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try {
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out.writeByte(0x3b); // gif trailer
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closeStream=true;
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} catch (e) {
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ok = false;
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}
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return ok;
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};
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/**
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* Resets some members so that a new stream can be started.
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* This method is actually called by the start method
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*/
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var reset = function reset() {
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// reset for subsequent use
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transIndex = 0;
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image = null;
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pixels = null;
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indexedPixels = null;
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colorTab = null;
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closeStream = false;
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firstFrame = true;
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};
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/**
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* * Sets frame rate in frames per second. Equivalent to
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* <code>setDelay(1000/fps)</code>.
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* @param fps
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* float frame rate (frames per second)
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*/
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var setFrameRate = exports.setFrameRate = function setFrameRate(fps) {
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if (fps != 0xf) delay = Math.round(100 / fps);
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};
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/**
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* Sets quality of color quantization (conversion of images to the maximum 256
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* colors allowed by the GIF specification). Lower values (minimum = 1)
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* produce better colors, but slow processing significantly. 10 is the
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* default, and produces good color mapping at reasonable speeds. Values
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* greater than 20 do not yield significant improvements in speed.
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* @param quality
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* int greater than 0.
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* @return
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*/
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var setQuality = exports.setQuality = function setQuality(quality) {
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if (quality < 1) quality = 1;
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sample = quality;
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};
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/**
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* Sets the GIF frame size. The default size is the size of the first frame
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* added if this method is not invoked.
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* @param w
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* int frame width.
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* @param h
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* int frame width.
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*/
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var setSize = exports.setSize = function setSize(w, h) {
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if (started && !firstFrame) return;
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width = w;
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height = h;
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if (width < 1) width = 320;
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if (height < 1) height = 240;
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sizeSet = true;
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};
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/**
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* Initiates GIF file creation on the given stream.
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* @param os
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* OutputStream on which GIF images are written.
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* @return false if initial write failed.
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*/
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var start = exports.start = function start() {
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reset();
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var ok = true;
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closeStream = false;
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out = new ByteArray();
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try {
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out.writeUTFBytes("GIF89a"); // header
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} catch (e) {
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ok = false;
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}
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return started = ok;
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};
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var cont = exports.cont = function cont() {
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reset();
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var ok = true;
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closeStream = false;
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out = new ByteArray();
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return started = ok;
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};
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/**
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* Analyzes image colors and creates color map.
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*/
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var analyzePixels = function analyzePixels() {
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var len = pixels.length;
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var nPix = len / 3;
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indexedPixels = [];
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var nq = new NeuQuant(pixels, len, sample);
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// initialize quantizer
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colorTab = nq.process(); // create reduced palette
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// map image pixels to new palette
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var k = 0;
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for (var j = 0; j < nPix; j++) {
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var index = nq.map(pixels[k++] & 0xff, pixels[k++] & 0xff, pixels[k++] & 0xff);
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usedEntry[index] = true;
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indexedPixels[j] = index;
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}
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pixels = null;
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colorDepth = 8;
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palSize = 7;
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// get closest match to transparent color if specified
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if (transparent !== null) {
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transIndex = findClosest(transparent);
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}
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};
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/**
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* Returns index of palette color closest to c
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*/
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var findClosest = function findClosest(c) {
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if (colorTab === null) return -1;
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var r = (c & 0xFF0000) >> 16;
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var g = (c & 0x00FF00) >> 8;
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var b = (c & 0x0000FF);
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var minpos = 0;
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var dmin = 256 * 256 * 256;
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var len = colorTab.length;
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for (var i = 0; i < len;) {
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var dr = r - (colorTab[i++] & 0xff);
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var dg = g - (colorTab[i++] & 0xff);
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var db = b - (colorTab[i] & 0xff);
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var d = dr * dr + dg * dg + db * db;
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var index = i / 3;
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if (usedEntry[index] && (d < dmin)) {
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dmin = d;
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minpos = index;
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}
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i++;
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}
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return minpos;
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};
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/**
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* Extracts image pixels into byte array "pixels
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*/
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var getImagePixels = function getImagePixels() {
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var w = width;
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var h = height;
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pixels = [];
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var data = image;
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var count = 0;
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for (var i = 0; i < h; i++) {
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for (var j = 0; j < w; j++) {
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var b = (i * w * 4) + j * 4;
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pixels[count++] = data[b];
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pixels[count++] = data[b + 1];
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pixels[count++] = data[b + 2];
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}
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}
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};
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/**
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* Writes Graphic Control Extension
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*/
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var writeGraphicCtrlExt = function writeGraphicCtrlExt() {
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out.writeByte(0x21); // extension introducer
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out.writeByte(0xf9); // GCE label
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out.writeByte(4); // data block size
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var transp;
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var disp;
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if (transparent === null) {
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transp = 0;
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disp = 0; // dispose = no action
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} else {
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transp = 1;
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disp = 2; // force clear if using transparent color
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}
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if (dispose >= 0) {
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disp = dispose & 7; // user override
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}
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disp <<= 2;
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// packed fields
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out.writeByte(0 | // 1:3 reserved
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disp | // 4:6 disposal
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0 | // 7 user input - 0 = none
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transp); // 8 transparency flag
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WriteShort(delay); // delay x 1/100 sec
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out.writeByte(transIndex); // transparent color index
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out.writeByte(0); // block terminator
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};
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/**
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* Writes Comment Extention
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*/
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var writeCommentExt = function writeCommentExt() {
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out.writeByte(0x21); // extension introducer
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out.writeByte(0xfe); // comment label
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out.writeByte(comment.length); // Block Size (s)
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out.writeUTFBytes(comment);
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out.writeByte(0); // block terminator
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};
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/**
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* Writes Image Descriptor
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*/
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var writeImageDesc = function writeImageDesc() {
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out.writeByte(0x2c); // image separator
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WriteShort(0); // image position x,y = 0,0
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WriteShort(0);
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WriteShort(width); // image size
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WriteShort(height);
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// packed fields
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if (firstFrame) {
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// no LCT - GCT is used for first (or only) frame
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out.writeByte(0);
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} else {
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// specify normal LCT
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out.writeByte(0x80 | // 1 local color table 1=yes
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0 | // 2 interlace - 0=no
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0 | // 3 sorted - 0=no
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0 | // 4-5 reserved
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palSize); // 6-8 size of color table
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}
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};
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/**
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* Writes Logical Screen Descriptor
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*/
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var writeLSD = function writeLSD() {
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// logical screen size
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WriteShort(width);
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WriteShort(height);
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// packed fields
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out.writeByte((0x80 | // 1 : global color table flag = 1 (gct used)
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0x70 | // 2-4 : color resolution = 7
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0x00 | // 5 : gct sort flag = 0
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palSize)); // 6-8 : gct size
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out.writeByte(0); // background color index
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out.writeByte(0); // pixel aspect ratio - assume 1:1
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};
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/**
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* Writes Netscape application extension to define repeat count.
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*/
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var writeNetscapeExt = function writeNetscapeExt() {
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out.writeByte(0x21); // extension introducer
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out.writeByte(0xff); // app extension label
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out.writeByte(11); // block size
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out.writeUTFBytes("NETSCAPE" + "2.0"); // app id + auth code
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out.writeByte(3); // sub-block size
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out.writeByte(1); // loop sub-block id
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WriteShort(repeat); // loop count (extra iterations, 0=repeat forever)
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out.writeByte(0); // block terminator
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};
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/**
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* Writes color table
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*/
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var writePalette = function writePalette() {
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out.writeBytes(colorTab);
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var n = (3 * 256) - colorTab.length;
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for (var i = 0; i < n; i++) out.writeByte(0);
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};
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var WriteShort = function WriteShort(pValue) {
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out.writeByte(pValue & 0xFF);
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out.writeByte((pValue >> 8) & 0xFF);
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};
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/**
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* Encodes and writes pixel data
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*/
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var writePixels = function writePixels() {
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var myencoder = new LZWEncoder(width, height, indexedPixels, colorDepth);
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myencoder.encode(out);
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};
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/**
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* Retrieves the GIF stream
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*/
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var stream = exports.stream = function stream() {
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return out;
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};
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var setProperties = exports.setProperties = function setProperties(has_start, is_first) {
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started = has_start;
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firstFrame = is_first;
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};
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return exports;
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};
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