/*
   * Pixastic Lib - Histogram - v0.1.0
   * Copyright (c) 2008 Jacob Seidelin, jseidelin@nihilogic.dk, http://blog.nihilogic.dk/
   * MIT License [http://www.opensource.org/licenses/mit-license.php]
   */
  
  Pixastic.Actions.histogram = {
          process : function(params) {
  
                  var average = !!(params.options.average);
                  var paint = !!(params.options.paint);
                  var color = params.options.color || "rgba(255,255,255,0.5)";
                  var values = [];
                  if (typeof params.options.returnValue != "object") {
                          params.options.returnValue = {values:[]};
                  }
                  var returnValue = params.options.returnValue;
                  if (typeof returnValue.values != "array") {
                          returnValue.values = [];
                  }
                  values = returnValue.values;
  
                  if (Pixastic.Client.hasCanvasImageData()) {
                          var data = Pixastic.prepareData(params);
                          params.useData = false;
  
                          for (var i=0;i<256;i++) {
                                  values[i] = 0;
                          }
  
                          var rect = params.options.rect;
                          var w = rect.width;
                          var h = rect.height;
                          var w4 = w*4;
                          var y = h;
                          do {
                                  var offsetY = (y-1)*w4;
                                  var x = w;
                                  do {
                                          var offset = offsetY + (x*4-4);
                                          var brightness = average ? 
                                                  Math.round((data[offset]+data[offset+1]+data[offset+2])/3)
                                                  : Math.round(data[offset]*0.3 + data[offset+1]*0.59 + data[offset+2]*0.11);
                                          values[brightness]++;
  
                                  } while (--x);
                          } while (--y);
  
                          if (paint) {
                                  var maxValue = 0;
                                  for (var i=0;i<256;i++) {
                                          if (values[i] > maxValue) {
                                                  maxValue = values[i];
                                          }
                                  }
                                  var heightScale = params.height / maxValue;
                                  var widthScale = params.width / 256;
                                  var ctx = params.canvas.getContext("2d");
                                  ctx.fillStyle = color;
                                  for (var i=0;i<256;i++) {
                                          ctx.fillRect(
                                                  i * widthScale, params.height - heightScale * values[i],
                                                  widthScale, values[i] * heightScale
                                          );
                                  }
                          }
  
                          returnValue.values = values;
  
                          return true;
                  }
          },
          checkSupport : function() {
                  return Pixastic.Client.hasCanvasImageData();
          }
  }