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gif-encoder

GIFEncoder from jsgif

Dieses Skript sollte nicht direkt installiert werden. Es handelt sich hier um eine Bibliothek für andere Skripte, welche über folgenden Befehl in den Metadaten eines Skriptes eingebunden wird // @require https://update.greasyfork.org/scripts/428487/1028787/gif-encoder.js 

/**
 * This class lets you encode animated GIF files
 * Base class :  http://www.java2s.com/Code/Java/2D-Graphics-GUI/AnimatedGifEncoder.htm
 * @author Kevin Weiner (original Java version - [email protected])
 * @author Thibault Imbert (AS3 version - bytearray.org)
 * @author Kevin Kwok (JavaScript version - https://github.com/antimatter15/jsgif)
 * @version 0.1 AS3 implementation
 */

GIFEncoder = function() {

	for (var i = 0, chr = {}; i < 256; i++)
		chr[i] = String.fromCharCode(i);

	function ByteArray() {
		this.bin = [];
	}

	ByteArray.prototype.getData = function() {
		for (var v = '', l = this.bin.length, i = 0; i < l; i++)
			v += chr[this.bin[i]];
		return v;
	};

	ByteArray.prototype.writeByte = function(val) {
		this.bin.push(val);
	};

	ByteArray.prototype.writeUTFBytes = function(string) {
		for (var l = string.length, i = 0; i < l; i++)
			this.writeByte(string.charCodeAt(i));
	};

	ByteArray.prototype.writeBytes = function(array, offset, length) {
		for (var l = length || array.length, i = offset || 0; i < l; i++)
			this.writeByte(array[i]);
	};

	var exports = {};
	var width; // image size
	var height;
	var transparent = null; // transparent color if given
	var transIndex; // transparent index in color table
	var repeat = -1; // no repeat
	var delay = 0; // frame delay (hundredths)
	var started = false; // ready to output frames
	var out;
	var image; // current frame
	var pixels; // BGR byte array from frame
	var indexedPixels; // converted frame indexed to palette
	var colorDepth; // number of bit planes
	var colorTab; // RGB palette
	var usedEntry = []; // active palette entries
	var palSize = 7; // color table size (bits-1)
	var dispose = -1; // disposal code (-1 = use default)
	var closeStream = false; // close stream when finished
	var firstFrame = true;
	var sizeSet = false; // if false, get size from first frame
	var sample = 10; // default sample interval for quantizer
	var comment = "Generated by jsgif (https://github.com/antimatter15/jsgif/)"; // default comment for generated gif

	/**
	 * Sets the delay time between each frame, or changes it for subsequent frames
	 * (applies to last frame added)
	 * int delay time in milliseconds
	 * @param ms
	 */

	var setDelay = exports.setDelay = function setDelay(ms) {
		delay = Math.round(ms / 10);
	};

	/**
	 * Sets the GIF frame disposal code for the last added frame and any
	 *
	 * subsequent frames. Default is 0 if no transparent color has been set,
	 * otherwise 2.
	 * @param code
	 * int disposal code.
	 */

	var setDispose = exports.setDispose = function setDispose(code) {
		if (code >= 0) dispose = code;
	};

	/**
	 * Sets the number of times the set of GIF frames should be played. Default is
	 * 1; 0 means play indefinitely. Must be invoked before the first image is
	 * added.
	 *
	 * @param iter
	 * int number of iterations.
	 * @return
	 */

	var setRepeat = exports.setRepeat = function setRepeat(iter) {
		if (iter >= 0) repeat = iter;
	};

	/**
	 * Sets the transparent color for the last added frame and any subsequent
	 * frames. Since all colors are subject to modification in the quantization
	 * process, the color in the final palette for each frame closest to the given
	 * color becomes the transparent color for that frame. May be set to null to
	 * indicate no transparent color.
	 * @param
	 * Color to be treated as transparent on display.
	 */

	var setTransparent = exports.setTransparent = function setTransparent(c) {
		transparent = c;
	};


	/**
	 * Sets the comment for the block comment
	 * @param
	 * string to be insterted as comment
	 */

	var setComment = exports.setComment = function setComment(c) {
		comment = c;
	};



	/**
	 * The addFrame method takes an incoming BitmapData object to create each frames
	 * @param
	 * BitmapData object to be treated as a GIF's frame
	 */

	var addFrame = exports.addFrame = function addFrame(im, is_imageData) {

		if ((im === null) || !started || out === null) {
			throw new Error("Please call start method before calling addFrame");
		}

		var ok = true;

		try {
			if (!is_imageData) {
				image = im.getImageData(0, 0, im.canvas.width, im.canvas.height).data;
				if (!sizeSet) setSize(im.canvas.width, im.canvas.height);
			} else {
				if(im instanceof ImageData) {
					image = im.data;
					if(!sizeset || width!=im.width || height!=im.height) {
						setSize(im.width,im.height);
					} else {
						
					}
				} else if(im instanceof Uint8ClampedArray) {
					if(im.length==(width*height*4)) {
						image=im;
					} else {
						console.log("Please set the correct size: ImageData length mismatch");
						ok=false;
					}
				} else {
					console.log("Please provide correct input");
					ok=false;
				}
			}
			getImagePixels(); // convert to correct format if necessary
			analyzePixels(); // build color table & map pixels

			if (firstFrame) {
				writeLSD(); // logical screen descriptior
				writePalette(); // global color table
				if (repeat >= 0) {
					// use NS app extension to indicate reps
					writeNetscapeExt();
				}
			}

			writeGraphicCtrlExt(); // write graphic control extension
			if (comment !== '') {
				writeCommentExt(); // write comment extension
			}
			writeImageDesc(); // image descriptor
			if (!firstFrame) writePalette(); // local color table
			writePixels(); // encode and write pixel data
			firstFrame = false;
		} catch (e) {
			ok = false;
		}

		return ok;
	};
	
	/**
	* @description: Downloads the encoded gif with the given name
	* No need of any conversion from the stream data (out) to base64
	* Solves the issue of large file sizes when there are more frames
	* and does not involve in creation of any temporary data in the process
	* so no wastage of memory, and speeds up the process of downloading
	* to just calling this function.
	* @parameter {String} filename filename used for downloading the gif
	*/
	
	var download = exports.download = function download(filename) {
		if(out===null || closeStream==false) {
			console.log("Please call start method and add frames and call finish method before calling download"); 
		} else {
			filename= filename !== undefined ? ( filename.endsWith(".gif")? filename: filename+".gif" ): "download.gif";
			var templink = document.createElement("a");
			templink.download=filename;
			templink.href= URL.createObjectURL(new Blob([new Uint8Array(out.bin)], {type : "image/gif" } ));
			templink.click();
		}
	}

	/**
	 * Adds final trailer to the GIF stream, if you don't call the finish method
	 * the GIF stream will not be valid.
	 */

	var finish = exports.finish = function finish() {

		if (!started) return false;

		var ok = true;
		started = false;

		try {
			out.writeByte(0x3b); // gif trailer
			closeStream=true;
		} catch (e) {
			ok = false;
		}

		return ok;
	};

	/**
	 * Resets some members so that a new stream can be started.
	 * This method is actually called by the start method
	 */

	var reset = function reset() {

		// reset for subsequent use
		transIndex = 0;
		image = null;
		pixels = null;
		indexedPixels = null;
		colorTab = null;
		closeStream = false;
		firstFrame = true;
	};

	/**
	 * * Sets frame rate in frames per second. Equivalent to
	 * <code>setDelay(1000/fps)</code>.
	 * @param fps
	 * float frame rate (frames per second)
	 */

	var setFrameRate = exports.setFrameRate = function setFrameRate(fps) {
		if (fps != 0xf) delay = Math.round(100 / fps);
	};

	/**
	 * Sets quality of color quantization (conversion of images to the maximum 256
	 * colors allowed by the GIF specification). Lower values (minimum = 1)
	 * produce better colors, but slow processing significantly. 10 is the
	 * default, and produces good color mapping at reasonable speeds. Values
	 * greater than 20 do not yield significant improvements in speed.
	 * @param quality
	 * int greater than 0.
	 * @return
	 */

	var setQuality = exports.setQuality = function setQuality(quality) {
		if (quality < 1) quality = 1;
		sample = quality;
	};

	/**
	 * Sets the GIF frame size. The default size is the size of the first frame
	 * added if this method is not invoked.
	 * @param w
	 * int frame width.
	 * @param h
	 * int frame width.
	 */

	var setSize = exports.setSize = function setSize(w, h) {

		if (started && !firstFrame) return;
		width = w;
		height = h;
		if (width < 1) width = 320;
		if (height < 1) height = 240;
		sizeSet = true;
	};

	/**
	 * Initiates GIF file creation on the given stream.
	 * @param os
	 * OutputStream on which GIF images are written.
	 * @return false if initial write failed.
	 */

	var start = exports.start = function start() {

		reset();
		var ok = true;
		closeStream = false;
		out = new ByteArray();
		try {
			out.writeUTFBytes("GIF89a"); // header
		} catch (e) {
			ok = false;
		}

		return started = ok;
	};

	var cont = exports.cont = function cont() {

		reset();
		var ok = true;
		closeStream = false;
		out = new ByteArray();

		return started = ok;
	};

	/**
	 * Analyzes image colors and creates color map.
	 */

	var analyzePixels = function analyzePixels() {

		var len = pixels.length;
		var nPix = len / 3;
		indexedPixels = [];
		var nq = new NeuQuant(pixels, len, sample);

		// initialize quantizer
		colorTab = nq.process(); // create reduced palette

		// map image pixels to new palette
		var k = 0;
		for (var j = 0; j < nPix; j++) {
			var index = nq.map(pixels[k++] & 0xff, pixels[k++] & 0xff, pixels[k++] & 0xff);
			usedEntry[index] = true;
			indexedPixels[j] = index;
		}

		pixels = null;
		colorDepth = 8;
		palSize = 7;

		// get closest match to transparent color if specified
		if (transparent !== null) {
			transIndex = findClosest(transparent);
		}
	};

	/**
	 * Returns index of palette color closest to c
	 */

	var findClosest = function findClosest(c) {

		if (colorTab === null) return -1;
		var r = (c & 0xFF0000) >> 16;
		var g = (c & 0x00FF00) >> 8;
		var b = (c & 0x0000FF);
		var minpos = 0;
		var dmin = 256 * 256 * 256;
		var len = colorTab.length;

		for (var i = 0; i < len;) {
			var dr = r - (colorTab[i++] & 0xff);
			var dg = g - (colorTab[i++] & 0xff);
			var db = b - (colorTab[i] & 0xff);
			var d = dr * dr + dg * dg + db * db;
			var index = i / 3;
			if (usedEntry[index] && (d < dmin)) {
				dmin = d;
				minpos = index;
			}
			i++;
		}
		return minpos;
	};

	/**
	 * Extracts image pixels into byte array "pixels
	 */

	var getImagePixels = function getImagePixels() {
		var w = width;
		var h = height;
		pixels = [];
		var data = image;
		var count = 0;

		for (var i = 0; i < h; i++) {

			for (var j = 0; j < w; j++) {

				var b = (i * w * 4) + j * 4;
				pixels[count++] = data[b];
				pixels[count++] = data[b + 1];
				pixels[count++] = data[b + 2];

			}

		}
	};

	/**
	 * Writes Graphic Control Extension
	 */

	var writeGraphicCtrlExt = function writeGraphicCtrlExt() {
		out.writeByte(0x21); // extension introducer
		out.writeByte(0xf9); // GCE label
		out.writeByte(4); // data block size
		var transp;
		var disp;
		if (transparent === null) {
			transp = 0;
			disp = 0; // dispose = no action
		} else {
			transp = 1;
			disp = 2; // force clear if using transparent color
		}
		if (dispose >= 0) {
			disp = dispose & 7; // user override
		}
		disp <<= 2;
		// packed fields
		out.writeByte(0 | // 1:3 reserved
			disp | // 4:6 disposal
			0 | // 7 user input - 0 = none
			transp); // 8 transparency flag

		WriteShort(delay); // delay x 1/100 sec
		out.writeByte(transIndex); // transparent color index
		out.writeByte(0); // block terminator
	};

	/**
	 * Writes Comment Extention
	 */

	var writeCommentExt = function writeCommentExt() {
		out.writeByte(0x21); // extension introducer
		out.writeByte(0xfe); // comment label
		out.writeByte(comment.length); // Block Size (s)
		out.writeUTFBytes(comment);
		out.writeByte(0); // block terminator
	};


	/**
	 * Writes Image Descriptor
	 */

	var writeImageDesc = function writeImageDesc() {

		out.writeByte(0x2c); // image separator
		WriteShort(0); // image position x,y = 0,0
		WriteShort(0);
		WriteShort(width); // image size
		WriteShort(height);

		// packed fields
		if (firstFrame) {
			// no LCT - GCT is used for first (or only) frame
			out.writeByte(0);
		} else {
			// specify normal LCT
			out.writeByte(0x80 | // 1 local color table 1=yes
				0 | // 2 interlace - 0=no
				0 | // 3 sorted - 0=no
				0 | // 4-5 reserved
				palSize); // 6-8 size of color table
		}
	};

	/**
	 * Writes Logical Screen Descriptor
	 */

	var writeLSD = function writeLSD() {

		// logical screen size
		WriteShort(width);
		WriteShort(height);
		// packed fields
		out.writeByte((0x80 | // 1 : global color table flag = 1 (gct used)
			0x70 | // 2-4 : color resolution = 7
			0x00 | // 5 : gct sort flag = 0
			palSize)); // 6-8 : gct size

		out.writeByte(0); // background color index
		out.writeByte(0); // pixel aspect ratio - assume 1:1
	};

	/**
	 * Writes Netscape application extension to define repeat count.
	 */

	var writeNetscapeExt = function writeNetscapeExt() {
		out.writeByte(0x21); // extension introducer
		out.writeByte(0xff); // app extension label
		out.writeByte(11); // block size
		out.writeUTFBytes("NETSCAPE" + "2.0"); // app id + auth code
		out.writeByte(3); // sub-block size
		out.writeByte(1); // loop sub-block id
		WriteShort(repeat); // loop count (extra iterations, 0=repeat forever)
		out.writeByte(0); // block terminator
	};

	/**
	 * Writes color table
	 */

	var writePalette = function writePalette() {
		out.writeBytes(colorTab);
		var n = (3 * 256) - colorTab.length;
		for (var i = 0; i < n; i++) out.writeByte(0);
	};

	var WriteShort = function WriteShort(pValue) {
		out.writeByte(pValue & 0xFF);
		out.writeByte((pValue >> 8) & 0xFF);
	};

	/**
	 * Encodes and writes pixel data
	 */

	var writePixels = function writePixels() {
		var myencoder = new LZWEncoder(width, height, indexedPixels, colorDepth);
		myencoder.encode(out);
	};

	/**
	 * Retrieves the GIF stream
	 */

	var stream = exports.stream = function stream() {
		return out;
	};

	var setProperties = exports.setProperties = function setProperties(has_start, is_first) {
		started = has_start;
		firstFrame = is_first;
	};

	return exports;

};