topical media & game development

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graphic-canvas-util-pixastic-actions-laplace.js / js



  /*
   * Pixastic Lib - Laplace filter - 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.laplace = {
          process : function(params) {
  
                  var strength = 1.0;
                  var invert = !!(params.options.invert);
                  var contrast = parseFloat(params.options.edgeStrength)||0;
  
                  var greyLevel = parseInt(params.options.greyLevel)||0;
  
                  contrast = -contrast;
  
                  if (Pixastic.Client.hasCanvasImageData()) {
                          var data = Pixastic.prepareData(params);
                          var dataCopy = Pixastic.prepareData(params, true)
  
                          var kernel = [
                                  [-1,         -1,         -1],
                                  [-1,         8,         -1],
                                  [-1,         -1,         -1]
                          ];
  
                          var weight = 1/8;
  
                          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 nextY = (y == h) ? y - 1 : y;
                                  var prevY = (y == 1) ? 0 : y-2;
  
                                  var offsetYPrev = prevY*w*4;
                                  var offsetYNext = nextY*w*4;
  
                                  var x = w;
                                  do {
                                          var offset = offsetY + (x*4-4);
  
                                          var offsetPrev = offsetYPrev + ((x == 1) ? 0 : x-2) * 4;
                                          var offsetNext = offsetYNext + ((x == w) ? x-1 : x) * 4;
          
                                          var r = ((-dataCopy[offsetPrev-4]
                                                  - dataCopy[offsetPrev]
                                                  - dataCopy[offsetPrev+4]
                                                  - dataCopy[offset-4]
                                                  - dataCopy[offset+4]
                                                  - dataCopy[offsetNext-4]
                                                  - dataCopy[offsetNext]
                                                  - dataCopy[offsetNext+4])
                                                  + dataCopy[offset] * 8) 
  						* weight;
          
                                          var g = ((-dataCopy[offsetPrev-3]
                                                  - dataCopy[offsetPrev+1]
                                                  - dataCopy[offsetPrev+5]
                                                  - dataCopy[offset-3]
                                                  - dataCopy[offset+5]
                                                  - dataCopy[offsetNext-3]
                                                  - dataCopy[offsetNext+1]
                                                  - dataCopy[offsetNext+5])
                                                  + dataCopy[offset+1] * 8)
  						* weight;
          
                                          var b = ((-dataCopy[offsetPrev-2]
                                                  - dataCopy[offsetPrev+2]
                                                  - dataCopy[offsetPrev+6]
                                                  - dataCopy[offset-2]
                                                  - dataCopy[offset+6]
                                                  - dataCopy[offsetNext-2]
                                                  - dataCopy[offsetNext+2]
                                                  - dataCopy[offsetNext+6])
                                                  + dataCopy[offset+2] * 8)
  						* weight;
  
                                          var brightness = ((r + g + b)/3) + greyLevel;
  
                                          if (contrast != 0) {
                                                  if (brightness > 127) {
                                                          brightness += ((brightness + 1) - 128) * contrast;
                                                  } else if (brightness < 127) {
                                                          brightness -= (brightness + 1) * contrast;
                                                  }
                                          }
                                          if (invert) {
                                                  brightness = 255 - brightness;
                                          }
                                          if (brightness < 0 ) brightness = 0;
                                          if (brightness > 255 ) brightness = 255;
  
                                          data[offset] = data[offset+1] = data[offset+2] = brightness;
  
                                  } while (--x);
                          } while (--y);
  
                          return true;
                  }
          },
          checkSupport : function() {
                  return Pixastic.Client.hasCanvasImageData();
          }
  }
  
  


(C) Æliens 20/2/2008

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