(function () {
  var ns = $.namespace('pskl.utils');
  var colorCache = {};
  ns.FrameUtils = {
    merge : function (frames) {
      var merged = null;
      if (frames.length) {
        merged = frames[0].clone();
        var w = merged.getWidth(), h = merged.getHeight();
        for (var i = 1 ; i < frames.length ; i++) {
          pskl.utils.FrameUtils.mergeFrames_(merged, frames[i]);
        }
      }
      return merged;
    },

    mergeFrames_ : function (frameA, frameB) {
      frameB.forEachPixel(function (p, col, row) {
        if (p != Constants.TRANSPARENT_COLOR) {
          frameA.setPixel(col, row, p);
        }
      });
    },

    /**
     * Alpha compositing using porter duff algorithm :
     * http://en.wikipedia.org/wiki/Alpha_compositing
     * http://keithp.com/~keithp/porterduff/p253-porter.pdf
     * @param  {String} strColor1 color over
     * @param  {String} strColor2 color under
     * @return {String} the composite color
     */
    mergePixels : function (strColor1, strColor2, globalOpacity1) {
      var col1 = pskl.utils.FrameUtils.toRgba(strColor1);
      var col2 = pskl.utils.FrameUtils.toRgba(strColor2);
      if (typeof globalOpacity1 == 'number') {
        col1 = JSON.parse(JSON.stringify(col1));
        col1.a = globalOpacity1 * col1.a;
      }
      var a = col1.a + col2.a * (1 - col1.a);

      var r = ((col1.r * col1.a + col2.r * col2.a * (1 - col1.a)) / a)|0;
      var g = ((col1.g * col1.a + col2.g * col2.a * (1 - col1.a)) / a)|0;
      var b = ((col1.b * col1.a + col2.b * col2.a * (1 - col1.a)) / a)|0;

      return 'rgba('+r+','+g+','+b+','+a+')';
    },

    /**
     * Convert a color defined as a string (hex, rgba, rgb, 'TRANSPARENT') to an Object with r,g,b,a properties.
     * r, g and b are integers between 0 and 255, a is a float between 0 and 1
     * @param  {String} c color as a string
     * @return {Object} {r:Number,g:Number,b:Number,a:Number}
     */
    toRgba : function (c) {
      if (colorCache[c]) {
        return colorCache[c];
      }
      var color, matches;
      if (c === 'TRANSPARENT') {
        color = {
          r : 0,
          g : 0,
          b : 0,
          a : 0
        };
      } else if (c.indexOf('rgba(') != -1) {
        matches = /rgba\((\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*,\s*(1|0\.\d+)\s*\)/.exec(c);
        color = {
          r : parseInt(matches[1],10),
          g : parseInt(matches[2],10),
          b : parseInt(matches[3],10),
          a : parseFloat(matches[4])
        };
      } else if (c.indexOf('rgb(') != -1) {
        matches = /rgb\((\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\)/.exec(c);
        color = {
          r : parseInt(matches[1],10),
          g : parseInt(matches[2],10),
          b : parseInt(matches[3],10),
          a : 1
        };
      } else {
        matches = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(c);
        color = {
          r : parseInt(matches[1], 16),
          g : parseInt(matches[2], 16),
          b : parseInt(matches[3], 16),
          a : 1
        };
      }
      colorCache[c] = color;
      return color;
    },

    /*
     * Create a pskl.model.Frame from an Image object.
     * Transparent pixels will either be converted to completely opaque or completely transparent pixels.
     * @param  {Image} image source image
     * @return {pskl.model.Frame} corresponding frame
     */
    createFromImage : function (image) {
      var w = image.width,
        h = image.height;
      var canvas = pskl.CanvasUtils.createCanvas(w, h);
      var context = canvas.getContext('2d');

      context.drawImage(image, 0,0,w,h,0,0,w,h);
      var imgData = context.getImageData(0,0,w,h).data;
      // Draw the zoomed-up pixels to a different canvas context
      var frame = [];
      for (var x=0;x<image.width;++x){
        frame[x] = [];
        for (var y=0;y<image.height;++y){
          // Find the starting index in the one-dimensional image data
          var i = (y*image.width + x)*4;
          var r = imgData[i  ];
          var g = imgData[i+1];
          var b = imgData[i+2];
          var a = imgData[i+3];
          if (a < 125) {
            frame[x][y] = "TRANSPARENT";
          } else {
            frame[x][y] = this.rgbToHex(r,g,b);
          }
        }
      }
      return frame;
    },

    /**
     * Convert a rgb(Number, Number, Number) color to hexadecimal representation
     * @param  {Number} r red value, between 0 and 255
     * @param  {Number} g green value, between 0 and 255
     * @param  {Number} b blue value, between 0 and 255
     * @return {String} hex representation of the color '#ABCDEF'
     */
    rgbToHex : function (r, g, b) {
      return "#" + this.componentToHex(r) + this.componentToHex(g) + this.componentToHex(b);
    },

    /**
     * Convert a color component (as a Number between 0 and 255) to its string hexa representation
     * @param  {Number} c component value, between 0 and 255
     * @return {String} eg. '0A'
     */
    componentToHex : function (c) {
      var hex = c.toString(16);
      return hex.length == 1 ? "0" + hex : hex;
    }
  };
})();