pixel array wrapper for haxing the canvas pixels

gistfile1.txt

  //dealing with the pixel data from the canvas is a pain
//gotta multiply everything by four everywhere all the time
//made an object to wrap up all that badness
  //a "pixel" is a 4 element array. 0 => R, 1 => G, 2 => B, 3 => A  

var PixelArray = root.PixelArray = function(ctx, w, h){
    this._pixels = ctx.getImageData(0, 0, w, h).data;
    this.w = w;
    this.h = h;
    this.numPixels = this._pixels.length / 4;
  };

  PixelArray.prototype.getPixel = function(x, y){
    if(x > this.w || y > this.h || x < 0 || y < 0) {
      throw "OUTTA BOUNDS!";
    }
    var pixelPosition = (y * this.w + x) * 4;
    return this._pixels.slice(pixelPosition, pixelPosition + 4);
  };

  PixelArray.prototype.getColor = function(pixel, alpha){
    if(alpha !== undefined){
      pixel[3] = alpha;
    }//is this a horrible thing to do? maybe... maybe...

    return "rgba(" + pixel.join(",") + ")";
  };


//oh and you also have to run this hack first to make this work because i guess pixel arrays are oh so super special

  if (typeof Uint8ClampedArray !== 'undefined') {
    Uint8ClampedArray.prototype.slice = Array.prototype.slice; //Firefox and Chrome
  } else if(typeof CanvasPixelArray!== 'undefined') {
    CanvasPixelArray.prototype.slice = Array.prototype.slice; //IE10 and IE9
  } else {
    // Deprecated browser
  }