AS3:How to change a colored Bitmap's BitmapData to black and white ?

Question

How can I change the bitmapdata of a coloured Bitmap to Black and White in AS3 ? I'm developing a simple image editor tool for a CMS in flash.

People should be able to switch the colour of the uploaded Bitmap to black and white. I want the bitmapdata itself to change So I can write it to a ByteArray with Adobe's JPGEncoder Class afterwards.

Answer 1

Well, just using getPixel and setPixel, and averaging the colors (I'm sure there may be another way to do this with a filter or something):

for(int i = 0; i < bitmapData.height; i++)
{
    for(int j = 0; j < bitmapData.width; j++)
    {
        var color:uint = bitmapData.getPixel(i, j);
        var red:uint = color & 0xFF0000 >> 16;
        var green:uint = color & 0x00FF00 >> 8;
        var blue:uint = color & 0x0000FF >> 0;
        var bwColor:uitn = red + green + blue / 3;
        bwColor = bwColor << 16 + bwColor << 8 + bwColor; // puts the average in each channel

        bitmapData.setPixel(i, j, bwColor);
    }
}

Answer 2

this would be the most elegant solution i presume (with source being you BitmapData):

const rc:Number = 1/3, gc:Number = 1/3, bc:Number = 1/3;
source.applyFilter(source.bitmapData, source.bitmapData.rect, new Point(), new ColorMatrixFilter([rc, gc, bc, 0, 0,rc, gc, bc, 0, 0, rc, gc, bc, 0, 0, 0, 0, 0, 1, 0]));

with flash.geom::Point and flash.filters::ColorMaxtrixFilter ...

ColorMatrixFilter allows many things, such as hue shifts, colorisation, lightening, darkening and desaturation and so on ... otherwise BitmapData::paletteMap and BitmapData::colorTransform are good complements ...

just wanted to note, that using the following

const rc:Number = 1/3, gc:Number = 1/2, bc:Number = 1/6;

looks a little more natural, since subjectively, #00FF00 is brighter than #FF0000, which in turn is brighter than #0000FF

good luck then ... ;)

Answer 3

Thanks for the responses. I'll give the two methods a try.

Answer 4

I tried both methods. Seems like the ColorMatrixFilter method works a lot faster when working with large images.

Is there some method to remove the Filter too? or shoud I change the ColorMatrixFilter values again?

Answer 5

Thanks Cookie, Copying the original bitmapdata was indeed the easiest solution to restore color.

   function clearColor() {
      colorbmd = new BitmapData(source.width, source.height);
      colorbmd = source.clone();
      //apply filter here    
    }
    function restoreColor() {
      source = colorbmd;
    }

I think once you've converted the image to black and white you can't go back (You lose information during the conversion). You will have to make a copy before you apply the filter. – CookieOfFortune

Answer 6

Can you please put an example?