gifwriter.worker.js

importScripts("GifWriter-0.1.0.js");

(function () {
  "use strict";

  var GifWriter = vividcode.image.GifWriter;
  var IndexedColorImage = vividcode.image.IndexedColorImage;
  var MedianCutColorReducer = vividcode.image.MedianCutColorReducer;

  this.onmessage = function (evt) {
    var msg = evt.data;

    var imageDataList = msg.imageDataList;
    var paletteSize = msg.paletteSize;
    var delayTimeInMS = msg.delayTimeInMS;

    var indexedColorImages = imageDataList.map(function (e) {
      return convertImgDataToIndexedColorImage(e, paletteSize);
    });

    var push = [].push;
    var os = {
        buffer: [],
        writeByte: function (b) { this.buffer.push(b) },
        writeBytes: function (bb) { push.apply(this.buffer, bb) },
    };
    var gifWriter = new GifWriter(os);
    gifWriter.writeHeader();
    gifWriter.writeLogicalScreenInfo({ width: msg.width, height: msg.height });
    gifWriter.writeLoopControlInfo(0);
    indexedColorImages.forEach(function (img) {
        gifWriter.writeTableBasedImageWithGraphicControl(img, { delayTimeInMS: delayTimeInMS });
    });
    gifWriter.writeTrailer();

    this.postMessage({ bytes: new Uint8Array(os.buffer) });
  };

  function convertImgDataToIndexedColorImage(imgData, paletteSize) {
    var reducer = new MedianCutColorReducer(imgData, paletteSize);
    var paletteData = reducer.process();
    var dat = Array.prototype.slice.call(imgData.data);
    var indexedColorImageData = [];
    for (var idx = 0, len = dat.length; idx < len; idx += 4) {
      var d = dat.slice(idx, idx+4); // r,g,b,a
      indexedColorImageData.push(reducer.map(d[0],d[1],d[2]));
    }
    return new IndexedColorImage({ width: imgData.width, height: imgData.height }, indexedColorImageData, paletteData);
  }
}).call(this);