p5.gif.js

// this is a slightly modified version of buzzfeed's SuperGif (https://github.com/buzzfeed/libgif-js)
// which is based on shachaf's jsgif (https://github.com/shachaf/jsgif)
(function(root, factory) {
  if (typeof define === 'function' && define.amd) {
    define([], factory);
  } else if (typeof exports === 'object') {
    module.exports = factory();
  } else {
    root.SuperGif = factory();
  }
}(this, function() {
  // Generic functions
  var bitsToNum = function(ba) {
    return ba.reduce(function(s, n) {
      return s * 2 + n;
    }, 0);
  };

  var byteToBitArr = function(bite) {
    var a = [];
    for (var i = 7; i >= 0; i--) {
      a.push(!!(bite & (1 << i)));
    }
    return a;
  };

  // Stream
  /**
   * @constructor
   */
  // Make compiler happy.
  var Stream = function(data) {
    this.data = data;
    this.len = this.data.length;
    this.pos = 0;

    this.readByte = function() {
      if (this.pos >= this.data.length) {
        throw new Error('Attempted to read past end of stream.');
      }
      if (data instanceof Uint8Array)
        return data[this.pos++];
      else
        return data.charCodeAt(this.pos++) & 0xFF;
    };

    this.readBytes = function(n) {
      var bytes = [];
      for (var i = 0; i < n; i++) {
        bytes.push(this.readByte());
      }
      return bytes;
    };

    this.read = function(n) {
      var s = '';
      for (var i = 0; i < n; i++) {
        s += String.fromCharCode(this.readByte());
      }
      return s;
    };

    this.readUnsigned = function() { // Little-endian.
      var a = this.readBytes(2);
      return (a[1] << 8) + a[0];
    };
  };

  var lzwDecode = function(minCodeSize, data) {
    // TODO: Now that the GIF parser is a bit different, maybe this should get an array of bytes instead of a String?
    var pos = 0; // Maybe this streaming thing should be merged with the Stream?
    var readCode = function(size) {
      var code = 0;
      for (var i = 0; i < size; i++) {
        if (data.charCodeAt(pos >> 3) & (1 << (pos & 7))) {
          code |= 1 << i;
        }
        pos++;
      }
      return code;
    };

    var output = [];

    var clearCode = 1 << minCodeSize;
    var eoiCode = clearCode + 1;

    var codeSize = minCodeSize + 1;

    var dict = [];

    var clear = function() {
      dict = [];
      codeSize = minCodeSize + 1;
      for (var i = 0; i < clearCode; i++) {
        dict[i] = [i];
      }
      dict[clearCode] = [];
      dict[eoiCode] = null;

    };

    var code;
    var last;

    while (true) {
      last = code;
      code = readCode(codeSize);

      if (code === clearCode) {
        clear();
        continue;
      }
      if (code === eoiCode) break;

      if (code < dict.length) {
        if (last !== clearCode) {
          dict.push(dict[last].concat(dict[code][0]));
        }
      } else {
        if (code !== dict.length) throw new Error('Invalid LZW code.');
        dict.push(dict[last].concat(dict[last][0]));
      }
      output.push.apply(output, dict[code]);

      if (dict.length === (1 << codeSize) && codeSize < 12) {
        // If we're at the last code and codeSize is 12, the next code will be a clearCode, and it'll be 12 bits long.
        codeSize++;
      }
    }

    // I don't know if this is technically an error, but some GIFs do it.
    //if (Math.ceil(pos / 8) !== data.length) throw new Error('Extraneous LZW bytes.');
    return output;
  };


  // The actual parsing; returns an object with properties.
  var parseGIF = function(st, handler) {
    handler || (handler = {});

    // LZW (GIF-specific)
    var parseCT = function(entries) { // Each entry is 3 bytes, for RGB.
      var ct = [];
      for (var i = 0; i < entries; i++) {
        ct.push(st.readBytes(3));
      }
      return ct;
    };

    var readSubBlocks = function() {
      var size, data;
      data = '';
      do {
        size = st.readByte();
        data += st.read(size);
      } while (size !== 0);
      return data;
    };

    var parseHeader = function() {
      var hdr = {};
      hdr.sig = st.read(3);
      hdr.ver = st.read(3);
      if (hdr.sig !== 'GIF') throw new Error('Not a GIF file.'); // XXX: This should probably be handled more nicely.
      hdr.width = st.readUnsigned();
      hdr.height = st.readUnsigned();

      var bits = byteToBitArr(st.readByte());
      hdr.gctFlag = bits.shift();
      hdr.colorRes = bitsToNum(bits.splice(0, 3));
      hdr.sorted = bits.shift();
      hdr.gctSize = bitsToNum(bits.splice(0, 3));

      hdr.bgColor = st.readByte();
      hdr.pixelAspectRatio = st.readByte(); // if not 0, aspectRatio = (pixelAspectRatio + 15) / 64
      if (hdr.gctFlag) {
        hdr.gct = parseCT(1 << (hdr.gctSize + 1));
      }
      handler.hdr && handler.hdr(hdr);
    };

    var parseExt = function(block) {
      var parseGCExt = function(block) {
        var blockSize = st.readByte(); // Always 4
        var bits = byteToBitArr(st.readByte());
        block.reserved = bits.splice(0, 3); // Reserved; should be 000.
        block.disposalMethod = bitsToNum(bits.splice(0, 3));
        block.userInput = bits.shift();
        block.transparencyGiven = bits.shift();

        block.delayTime = st.readUnsigned();

        block.transparencyIndex = st.readByte();

        block.terminator = st.readByte();

        handler.gce && handler.gce(block);
      };

      var parseComExt = function(block) {
        block.comment = readSubBlocks();
        handler.com && handler.com(block);
      };

      var parsePTExt = function(block) {
        // No one *ever* uses this. If you use it, deal with parsing it yourself.
        var blockSize = st.readByte(); // Always 12
        block.ptHeader = st.readBytes(12);
        block.ptData = readSubBlocks();
        handler.pte && handler.pte(block);
      };

      var parseAppExt = function(block) {
        var parseNetscapeExt = function(block) {
          var blockSize = st.readByte(); // Always 3
          block.unknown = st.readByte(); // ??? Always 1? What is this?
          block.iterations = st.readUnsigned();
          block.terminator = st.readByte();
          handler.app && handler.app.NETSCAPE && handler.app.NETSCAPE(block);
        };

        var parseUnknownAppExt = function(block) {
          block.appData = readSubBlocks();
          // FIXME: This won't work if a handler wants to match on any identifier.
          handler.app && handler.app[block.identifier] && handler.app[block.identifier](block);
        };

        var blockSize = st.readByte(); // Always 11
        block.identifier = st.read(8);
        block.authCode = st.read(3);
        switch (block.identifier) {
          case 'NETSCAPE':
            parseNetscapeExt(block);
            break;
          default:
            parseUnknownAppExt(block);
            break;
        }
      };

      var parseUnknownExt = function(block) {
        block.data = readSubBlocks();
        handler.unknown && handler.unknown(block);
      };

      block.label = st.readByte();
      switch (block.label) {
        case 0xF9:
          block.extType = 'gce';
          parseGCExt(block);
          break;
        case 0xFE:
          block.extType = 'com';
          parseComExt(block);
          break;
        case 0x01:
          block.extType = 'pte';
          parsePTExt(block);
          break;
        case 0xFF:
          block.extType = 'app';
          parseAppExt(block);
          break;
        default:
          block.extType = 'unknown';
          parseUnknownExt(block);
          break;
      }
    };

    var parseImg = function(img) {
      var deinterlace = function(pixels, width) {
        // Of course this defeats the purpose of interlacing. And it's *probably*
        // the least efficient way it's ever been implemented. But nevertheless...
        var newPixels = new Array(pixels.length);
        var rows = pixels.length / width;
        var cpRow = function(toRow, fromRow) {
          var fromPixels = pixels.slice(fromRow * width, (fromRow + 1) * width);
          newPixels.splice.apply(newPixels, [toRow * width, width].concat(fromPixels));
        };

        // See appendix E.
        var offsets = [0, 4, 2, 1];
        var steps = [8, 8, 4, 2];

        var fromRow = 0;
        for (var pass = 0; pass < 4; pass++) {
          for (var toRow = offsets[pass]; toRow < rows; toRow += steps[pass]) {
            cpRow(toRow, fromRow);
            fromRow++;
          }
        }

        return newPixels;
      };

      img.leftPos = st.readUnsigned();
      img.topPos = st.readUnsigned();
      img.width = st.readUnsigned();
      img.height = st.readUnsigned();

      var bits = byteToBitArr(st.readByte());
      img.lctFlag = bits.shift();
      img.interlaced = bits.shift();
      img.sorted = bits.shift();
      img.reserved = bits.splice(0, 2);
      img.lctSize = bitsToNum(bits.splice(0, 3));

      if (img.lctFlag) {
        img.lct = parseCT(1 << (img.lctSize + 1));
      }

      img.lzwMinCodeSize = st.readByte();

      var lzwData = readSubBlocks();

      img.pixels = lzwDecode(img.lzwMinCodeSize, lzwData);

      if (img.interlaced) { // Move
        img.pixels = deinterlace(img.pixels, img.width);
      }

      handler.img && handler.img(img);
    };

    var parseBlock = function() {
      var block = {};
      block.sentinel = st.readByte();

      switch (String.fromCharCode(block.sentinel)) { // For ease of matching
        case '!':
          block.type = 'ext';
          parseExt(block);
          break;
        case ',':
          block.type = 'img';
          parseImg(block);
          break;
        case ';':
          block.type = 'eof';
          handler.eof && handler.eof(block);
          break;
        default:
          throw new Error('Unknown block: 0x' + block.sentinel.toString(16)); // TODO: Pad this with a 0.
      }

      if (block.type !== 'eof') setTimeout(parseBlock, 0);
    };

    var parse = function() {
      parseHeader();
      setTimeout(parseBlock, 0);
    };

    parse();
  };

  var SuperGif = function(opts) {
    var options = {
      //viewport position
      vp_l: 0,
      vp_t: 0,
      vp_w: null,
      vp_h: null,
      //canvas sizes
      c_w: null,
      c_h: null,
      auto_play: true
    };
    for (var i in opts) {
      options[i] = opts[i];
    }
    if (options.vp_w && options.vp_h) options.is_vp = true;

    var stream;
    var hdr;

    var loadError = null;
    var loading = false;

    var transparency = null;
    var delay = null;
    var disposalMethod = null;
    var disposalRestoreFromIdx = null;
    var lastDisposalMethod = null;
    var frame = null;
    var lastImg = null;

    var playing = true;
    var forward = true;

    var ctx_scaled = false;

    var frames = [];
    var frameOffsets = []; // elements have .x and .y properties

    var gif = document.createElement('img');
    gif.src = options.gif;

    var onEndListener = (options.hasOwnProperty('on_end') ? options.on_end : null);
    var loopDelay = (options.hasOwnProperty('loop_delay') ? options.loop_delay : 0);
    var overrideLoopMode = (options.hasOwnProperty('loop_mode') ? options.loop_mode : 'auto');
    var drawWhileLoading = false;

    var clear = function() {
      transparency = null;
      delay = null;
      lastDisposalMethod = disposalMethod;
      disposalMethod = null;
      frame = null;
    };

    // XXX: There's probably a better way to handle catching exceptions when
    // callbacks are involved.
    var doParse = function() {
      try {
        parseGIF(stream, handler);
      } catch (err) {
        doLoadError('parse');
      }
    };

    var setSizes = function(w, h) {
      pGraphics.resize(w, h);
      pGraphics.width = w;
      pGraphics.height = h;
    };

    var setFrameOffset = function(frame, offset) {
      if (!frameOffsets[frame]) {
        frameOffsets[frame] = offset;
        return;
      }
      if (typeof offset.x !== 'undefined') {
        frameOffsets[frame].x = offset.x;
      }
      if (typeof offset.y !== 'undefined') {
        frameOffsets[frame].y = offset.y;
      }
    };

    var doLoadError = function(originOfError) {
      loadError = originOfError;
      frames = [];
    };

    var doHdr = function(_hdr) {
      hdr = _hdr;
      setSizes(hdr.width, hdr.height);
    };

    var doGCE = function(gce) {
      pushFrame();
      clear();
      transparency = gce.transparencyGiven ? gce.transparencyIndex : null;
      delay = gce.delayTime;
      disposalMethod = gce.disposalMethod;
      // We don't have much to do with the rest of GCE.
    };

    var pushFrame = function() {
      if (!frame) return;
      frames.push({
        data: frame.getImageData(0, 0, hdr.width, hdr.height),
        delay: delay
      });
      frameOffsets.push({
        x: 0,
        y: 0
      });
    };

    var doImg = function(img) {
      if (!frame) frame = tmpCanvas.getContext('2d');

      var currIdx = frames.length;

      //ct = color table, gct = global color table
      var ct = img.lctFlag ? img.lct : hdr.gct; // TODO: What if neither exists?

      /*
      Disposal method indicates the way in which the graphic is to
      be treated after being displayed.

      Values :    0 - No disposal specified. The decoder is
                      not required to take any action.
                  1 - Do not dispose. The graphic is to be left
                      in place.
                  2 - Restore to background color. The area used by the
                      graphic must be restored to the background color.
                  3 - Restore to previous. The decoder is required to
                      restore the area overwritten by the graphic with
                      what was there prior to rendering the graphic.

                      Importantly, "previous" means the frame state
                      after the last disposal of method 0, 1, or 2.
      */
      if (currIdx > 0) {
        if (lastDisposalMethod === 3) {
          // Restore to previous
          // If we disposed every frame including first frame up to this point, then we have
          // no composited frame to restore to. In this case, restore to background instead.
          if (disposalRestoreFromIdx !== null) {
            frame.putImageData(frames[disposalRestoreFromIdx].data, 0, 0);
          } else {
            frame.clearRect(lastImg.leftPos, lastImg.topPos, lastImg.width, lastImg.height);
          }
        } else {
          disposalRestoreFromIdx = currIdx - 1;
        }

        if (lastDisposalMethod === 2) {
          // Restore to background color
          // Browser implementations historically restore to transparent; we do the same.
          // http://www.wizards-toolkit.org/discourse-server/viewtopic.php?f=1&t=21172#p86079
          frame.clearRect(lastImg.leftPos, lastImg.topPos, lastImg.width, lastImg.height);
        }
      }
      // else, Undefined/Do not dispose.
      // frame contains final pixel data from the last frame; do nothing

      //Get existing pixels for img region after applying disposal method
      var imgData = frame.getImageData(img.leftPos, img.topPos, img.width, img.height);

      //apply color table colors
      var cdd = imgData.data;
      img.pixels.forEach(function(pixel, i) {
        // imgData.data === [R,G,B,A,R,G,B,A,...]
        if (pixel !== transparency) {
          cdd[i * 4 + 0] = ct[pixel][0];
          cdd[i * 4 + 1] = ct[pixel][1];
          cdd[i * 4 + 2] = ct[pixel][2];
          cdd[i * 4 + 3] = 255; // Opaque.
        }
      });
      imgData.data.set(cdd);

      frame.putImageData(imgData, img.leftPos, img.topPos);

      if (!ctx_scaled) {
        ctx_scaled = true;
      }

      lastImg = img;
    };

    var player = (function() {
      var i = -1;
      var iterationCount = 0;

      var showingInfo = false;
      var pinned = false;

      /**
       * Gets the index of the frame "up next".
       * @returns {number}
       */
      var getNextFrameNo = function() {
        var delta = (forward ? 1 : -1);
        return (i + delta + frames.length) % frames.length;
      };

      var stepFrame = function(amount) { // XXX: Name is confusing.
        i = i + amount;

        putFrame();
      };

      var completeLoop = function() {
        if (onEndListener !== null)
          onEndListener(gif);
        iterationCount++;
      };

      var step = (function() {
        var stepping = false;

        var doStep = function() {
          stepping = playing;
          if (!stepping) return;

          stepFrame(1);
          var delay = frames[i].delay * 10;
          if (!delay) delay = 100; // FIXME: Should this even default at all? What should it be?

          var nextFrameNo = getNextFrameNo();
          if (nextFrameNo === 0) {
            delay += loopDelay;
            setTimeout(completeLoop, delay - 1);
          }

          if ((overrideLoopMode !== false || nextFrameNo !== 0 || iterationCount < 0))
            setTimeout(doStep, delay);

        };

        return function() {
          if (!stepping) setTimeout(doStep, 0);
        };
      }());

      var putFrame = function() {
        var offset;
        i = parseInt(i, 10);

        if (i > frames.length - 1) {
          i = 0;
        }

        if (i < 0) {
          i = 0;
        }

        offset = frameOffsets[i];

        tmpCanvas.getContext("2d").putImageData(frames[i].data, offset.x, offset.y);
      };

      var play = function() {
        playing = true;
        step();
      };

      var pause = function() {
        playing = false;
      };



      return {
        init: function() {
          if (loadError) return;

          if (options.auto_play) {
            step();
          } else {
            i = 0;
            putFrame();
          }
        },
        step: step,
        play: play,
        pause: pause,
        playing: playing,
        move_relative: stepFrame,
        current_frame: function() {
          return i;
        },
        length: function() {
          return frames.length;
        },
        move_to: function(frame_idx) {
          i = frame_idx;
          putFrame();
        },
        get_frames: function() {
          return frames;
        },
        buffer: function() {
          return pGraphics;
        },
        get_playing: function() {
          return playing;
        },
      };
    }());

    var doNothing = function() {};
    /**
     * @param{boolean=} draw Whether to draw progress bar or not; this is not idempotent because of translucency.
     *                       Note that this means that the text will be unsynchronized with the progress bar on non-frames;
     *                       but those are typically so small (GCE etc.) that it doesn't really matter. TODO: Do this properly.
     */
    var withProgress = function(fn, draw) {
      return function(block) {
        fn(block);
      };
    };


    var handler = {
      hdr: withProgress(doHdr),
      gce: withProgress(doGCE),
      com: withProgress(doNothing),
      // I guess that's all for now.
      app: {
        // TODO: Is there much point in actually supporting iterations?
        NETSCAPE: withProgress(doNothing)
      },
      img: withProgress(doImg, true),
      eof: function(block) {
        pushFrame();
        player.init();
        loading = false;
        console.log('ok');
        if (load_callback) {
          load_callback(gif);
        }

      }
    };

    var init = function() {
      pGraphics = options.p5inst.createImage(0, 0);
      tmpCanvas = pGraphics.canvas;

      initialized = true;
    };

    var get_canvas_scale = function() {
      var scale;
      if (options.max_width && hdr && hdr.width > options.max_width) {
        scale = options.max_width / hdr.width;
      } else {
        scale = 1;
      }
      return scale;
    };

    var tmpCanvas, pGraphics;
    var initialized = false;
    var load_callback = false;

    var load_setup = function(callback) {
      if (loading) return false;
      if (callback) load_callback = callback;
      else load_callback = false;

      loading = true;
      frames = [];
      clear();
      disposalRestoreFromIdx = null;
      lastDisposalMethod = null;
      frame = null;
      lastImg = null;

      return true;
    };

    return {
      // play controls
      play: player.play,
      pause: player.pause,
      move_relative: player.move_relative,
      move_to: player.move_to,

      // getters for instance vars
      get_playing: player.get_playing,
      get_canvas: function() {
        return canvas;
      },
      get_canvas_scale: function() {
        return get_canvas_scale();
      },
      get_loading: function() {
        return loading;
      },
      get_auto_play: function() {
        return options.auto_play;
      },
      get_length: function() {
        return player.length();
      },
      get_current_frame: function() {
        return player.current_frame();
      },
      get_frames: function() {
        return player.get_frames();
      },
      buffer: function() {
        return player.buffer();
      },
      load_url: function(src, callback) {
        if (!load_setup(callback)) return;
        var h = new XMLHttpRequest();
        h.overrideMimeType('text/plain; charset=x-user-defined');
        h.onloadstart = function() {
          // Wait until connection is opened to replace the gif element with a canvas to avoid a blank img
          if (!initialized) init();
        };
        h.onload = function(e) {
          stream = new Stream(h.responseText);
          setTimeout(doParse, 0);
        };
        h.onerror = function() {
          doLoadError('xhr');
        };
        h.open('GET', src, true);
        h.send();
      },
      load: function(callback) {
        this.load_url(gif.src, callback);
      },
      load_raw: function(arr, callback) {
        if (!load_setup(callback)) return;
        if (!initialized) init();
        stream = new Stream(arr);
        setTimeout(doParse, 0);
      },
      set_frame_offset: setFrameOffset
    };
  };

  return SuperGif;
}));


(function() {

p5.prototype.loadGif = function(url, cb) {
  var gif = new SuperGif({
    gif: url,
    p5inst: this
  });

  gif.load(cb);

  var p5graphic = gif.buffer();

  p5graphic.play = gif.play;
  p5graphic.pause = gif.pause;
  p5graphic.playing = gif.get_playing;
  p5graphic.frames = gif.get_frames;
  p5graphic.totalFrames = gif.get_length;

  p5graphic.loaded = function() {
    return !gif.get_loading();
  };

  p5graphic.frame = function(num) {
    if (typeof num === 'number') {
      gif.move_to(num);
    } else {
      return gif.get_current_frame();
    }
  };

  return p5graphic;
};

p5.prototype.loadRawGif = function(data, cb) {
  var gif = new SuperGif({
    gif: '',
    p5inst: this
  });

  gif.load_raw(data, cb);

  var p5graphic = gif.buffer();
  p5graphic.play = gif.play;
  p5graphic.pause = gif.pause;
  p5graphic.playing = gif.get_playing;
  p5graphic.frames = gif.get_frames;
  p5graphic.totalFrames = gif.get_length;

  p5graphic.loaded = function() {
    return !gif.get_loading();
  };

  p5graphic.frame = function(num) {
    if (typeof num === 'number') {
      gif.move_to(num);
    } else {
      return gif.get_current_frame();
    }
  };

  return p5graphic;
};

})();