AS3 - How to remove all black and grey from bitmap, but retain color?

Question

I'd like to be able to alter an image (specifically a bitmap) in order to replace all dark grey and black pixels with white in ActionScript 3, but maintain all other colors in the image. I am familiar with ColorMatrixFilter and bitmapdata.threshold, but I don't know how to use them to either target the colors I want to remove or check within a specific range of colors. Is there any (efficient) way to go about doing this?

Thanks for any help you can offer.

Answer 1

The AS3 API gives pretty good documentation on how to use the treshhold value. You can find it here. Their example actually checks for a certain range of colors. I've modified their example to work for your problem. I haven't tested it, so it might need some tweaking.

var bmd2:BitmapData = new BitmapData(200, 200, true, 0xFFCCCCCC);
var pt:Point = new Point(0, 0);
var rect:Rectangle = new Rectangle(0, 0, 200, 200);
var threshold:uint =  0x00A9A9A9; //Dark Grey
var color:uint = 0x00000000; //Replacement color (white)
var maskColor:uint = 0xFFFFFFFF; //What channels to affect (this is the default).
bmd2.threshold(bmd1, rect, pt, ">", threshold, color, maskColor, true);

Another option would be to use a double for loop that iterates over all pixels and takes a certain action based on the value of the pixel.

for(var y:int = 0; y < height; y++){
  for(var x:int = 0; x < width; x++){
    var currentPixel:uint = image.getPixel( x, y );
    if(currentPixel != color){
      image.setPixel( destPoint.x + j, destPoint.y + i, currentPixel );
    }          
  }
}