/*
  * 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.colorhistogram = {
  
          array256 : function(default_value) {
                  arr = [];
                  for (var i=0; i<256; i++) { arr[i] = default_value; }
                  return arr
          },
   
          process : function(params) {
                  var values = [];
                  if (typeof params.options.returnValue != "object") {
                          params.options.returnValue = {rvals:[], gvals:[], bvals:[]};
                  }
                  var paint = !!(params.options.paint);
  
                  var returnValue = params.options.returnValue;
                  if (typeof returnValue.values != "array") {
                          returnValue.rvals = [];
                          returnValue.gvals = [];
                          returnValue.bvals = [];
                  }
   
                  if (Pixastic.Client.hasCanvasImageData()) {
                          var data = Pixastic.prepareData(params);
                          params.useData = false;
   
                          var rvals = this.array256(0);
                          var gvals = this.array256(0);
                          var bvals = this.array256(0);
   
                          var rect = params.options.rect;
  
                          var p = rect.width*rect.height;
                          var pix = p*4;
                          while (p--) {
                                  rvals[data[pix-=4]]++;
                                  gvals[data[pix+1]]++;
                                  bvals[data[pix+2]]++;
                          }
   
                          returnValue.rvals = rvals;
                          returnValue.gvals = gvals;
                          returnValue.bvals = bvals;
  
                          if (paint) {
                                  var ctx = params.canvas.getContext("2d");
                                  var vals = [rvals, gvals, bvals];
                                  for (var v=0;v<3;v++) {
                                          var yoff = (v+1) * params.height / 3;
                                          var maxValue = 0;
                                          for (var i=0;i<256;i++) {
                                                  if (vals[v][i] > maxValue)
                                                          maxValue = vals[v][i];
                                          }
                                          var heightScale = params.height / 3 / maxValue;
                                          var widthScale = params.width / 256;
                                          if (v==0) ctx.fillStyle = "rgba(255,0,0,0.5)";
                                          else if (v==1) ctx.fillStyle = "rgba(0,255,0,0.5)";
                                          else if (v==2) ctx.fillStyle = "rgba(0,0,255,0.5)";
                                          for (var i=0;i<256;i++) {
                                                  ctx.fillRect(
                                                          i * widthScale, params.height - heightScale * vals[v][i] - params.height + yoff,
                                                          widthScale, vals[v][i] * heightScale
                                                  );
                                          }
                                  }
                          }
                          return true;
                  }
          },
  
          checkSupport : function() {
                  return Pixastic.Client.hasCanvasImageData();
          }
  }