var effects = {
  'gray': function(data){
    for(var i = 0; i < data.length; i+=4) {
      var r = data[i];
      var g = data[i+1];
      var b = data[i+2];
      var brightness = (3*r+4*g+b)>>>3;
      data[i] = brightness;
      data[i+1] = brightness;
      data[i+2] = brightness;
    }
  },
  'negative': function(data){
    for(var i = 0; i < data.length; i += 4) {
      // red
      data[i] = 255 - data[i];
      // green
      data[i + 1] = 255 - data[i + 1];
      // blue
      data[i + 2] = 255 - data[i + 2];
    }
  },
  'sepia': function(data){
    var r = [0, 0, 0, 1, 1, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 12, 12, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 17, 18, 19, 19, 20, 21, 22, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 39, 40, 41, 42, 44, 45, 47, 48, 49, 52, 54, 55, 57, 59, 60, 62, 65, 67, 69, 70, 72, 74, 77, 79, 81, 83, 86, 88, 90, 92, 94, 97, 99, 101, 103, 107, 109, 111, 112, 116, 118, 120, 124, 126, 127, 129, 133, 135, 136, 140, 142, 143, 145, 149, 150, 152, 155, 157, 159, 162, 163, 165, 167, 170, 171, 173, 176, 177, 178, 180, 183, 184, 185, 188, 189, 190, 192, 194, 195, 196, 198, 200, 201, 202, 203, 204, 206, 207, 208, 209, 211, 212, 213, 214, 215, 216, 218, 219, 219, 220, 221, 222, 223, 224, 225, 226, 227, 227, 228, 229, 229, 230, 231, 232, 232, 233, 234, 234, 235, 236, 236, 237, 238, 238, 239, 239, 240, 241, 241, 242, 242, 243, 244, 244, 245, 245, 245, 246, 247, 247, 248, 248, 249, 249, 249, 250, 251, 251, 252, 252, 252, 253, 254, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255],
      g = [0, 0, 1, 2, 2, 3, 5, 5, 6, 7, 8, 8, 10, 11, 11, 12, 13, 15, 15, 16, 17, 18, 18, 19, 21, 22, 22, 23, 24, 26, 26, 27, 28, 29, 31, 31, 32, 33, 34, 35, 35, 37, 38, 39, 40, 41, 43, 44, 44, 45, 46, 47, 48, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 79, 80, 81, 83, 84, 85, 86, 88, 89, 90, 92, 93, 94, 95, 96, 97, 100, 101, 102, 103, 105, 106, 107, 108, 109, 111, 113, 114, 115, 117, 118, 119, 120, 122, 123, 124, 126, 127, 128, 129, 131, 132, 133, 135, 136, 137, 138, 140, 141, 142, 144, 145, 146, 148, 149, 150, 151, 153, 154, 155, 157, 158, 159, 160, 162, 163, 164, 166, 167, 168, 169, 171, 172, 173, 174, 175, 176, 177, 178, 179, 181, 182, 183, 184, 186, 186, 187, 188, 189, 190, 192, 193, 194, 195, 195, 196, 197, 199, 200, 201, 202, 202, 203, 204, 205, 206, 207, 208, 208, 209, 210, 211, 212, 213, 214, 214, 215, 216, 217, 218, 219, 219, 220, 221, 222, 223, 223, 224, 225, 226, 226, 227, 228, 228, 229, 230, 231, 232, 232, 232, 233, 234, 235, 235, 236, 236, 237, 238, 238, 239, 239, 240, 240, 241, 242, 242, 242, 243, 244, 245, 245, 246, 246, 247, 247, 248, 249, 249, 249, 250, 251, 251, 252, 252, 252, 253, 254, 255],
      b = [53, 53, 53, 54, 54, 54, 55, 55, 55, 56, 57, 57, 57, 58, 58, 58, 59, 59, 59, 60, 61, 61, 61, 62, 62, 63, 63, 63, 64, 65, 65, 65, 66, 66, 67, 67, 67, 68, 69, 69, 69, 70, 70, 71, 71, 72, 73, 73, 73, 74, 74, 75, 75, 76, 77, 77, 78, 78, 79, 79, 80, 81, 81, 82, 82, 83, 83, 84, 85, 85, 86, 86, 87, 87, 88, 89, 89, 90, 90, 91, 91, 93, 93, 94, 94, 95, 95, 96, 97, 98, 98, 99, 99, 100, 101, 102, 102, 103, 104, 105, 105, 106, 106, 107, 108, 109, 109, 110, 111, 111, 112, 113, 114, 114, 115, 116, 117, 117, 118, 119, 119, 121, 121, 122, 122, 123, 124, 125, 126, 126, 127, 128, 129, 129, 130, 131, 132, 132, 133, 134, 134, 135, 136, 137, 137, 138, 139, 140, 140, 141, 142, 142, 143, 144, 145, 145, 146, 146, 148, 148, 149, 149, 150, 151, 152, 152, 153, 153, 154, 155, 156, 156, 157, 157, 158, 159, 160, 160, 161, 161, 162, 162, 163, 164, 164, 165, 165, 166, 166, 167, 168, 168, 169, 169, 170, 170, 171, 172, 172, 173, 173, 174, 174, 175, 176, 176, 177, 177, 177, 178, 178, 179, 180, 180, 181, 181, 181, 182, 182, 183, 184, 184, 184, 185, 185, 186, 186, 186, 187, 188, 188, 188, 189, 189, 189, 190, 190, 191, 191, 192, 192, 193, 193, 193, 194, 194, 194, 195, 196, 196, 196, 197, 197, 197, 198, 199];
    for (var i=0; i < data.length; i+=4) {
      // change image colors
      data[i] = r[data[i]];
      data[i+1] = g[data[i+1]];
      data[i+2] = b[data[i+2]];
      // apply noise
      var noise = 20;
      if (noise > 0) {
        var noise = Math.round(noise - Math.random() * noise);
        for(var j=0; j<3; j++){
            var iPN = noise + data[i+j];
            data[i+j] = (iPN > 255) ? 255 : iPN;
        }
      }
    }
  }
};