Color matrix to change dark color

I try to make a function to colorize image - desaturate and replace dark color with supplied RGB color.

I have found similar function from Mario Klingemann AS3 ColorMatrix library, which replace light color while preserving dark.

public function colorize(rgb:int, amount:Number=1):void
    {
        const LUMA_R:Number = 0.212671;
        const LUMA_G:Number = 0.71516;
        const LUMA_B:Number = 0.072169;

        var r:Number;
        var g:Number;
        var b:Number;
        var inv_amount:Number;

        r = (((rgb >> 16) & 0xFF) / 0xFF);
        g = (((rgb >> 8) & 0xFF) / 0xFF);
        b = ((rgb & 0xFF) / 0xFF);
        inv_amount = (1 - amount);

        concat([(inv_amount + ((amount * r) * LUMA_R)), ((amount * r) * LUMA_G), ((amount * r) * LUMA_B), 0, 0, 
                ((amount * g) * LUMA_R), (inv_amount + ((amount * g) * LUMA_G)), ((amount * g) * LUMA_B), 0, 0, 
                ((amount * b) * LUMA_R), ((amount * b) * LUMA_G), (inv_amount + ((amount * b) * LUMA_B)), 0, 0, 
                0, 0, 0, 1, 0]);
    }

I tried to modify the matrix but with no success. Please could you provide me any help or link to information or code that make me move forward a bit.

You could try to use the method above, but before you apply it you invert the image and the color. Then after applying the matrix, you invert the image again.