CODEWITHSUNDEEP
colorsalphaargb
user1148358
user1148358

Reputation:

Combine/mix two ARGB (alpha - red, green blue) values

I have been struggling to combine two ARGB values - despite a lot of reading e.g. here... How to mix two ARGB pixels?

I am not getting the result I am expecting - or what I am expecting is wrong; if someone could suggest a function to do this, it would be great.

I want to combine:

  1. ColorA (red = 255, green = 255, blue = 0, alpha = 100)

  2. ColorB (red = 0, green = 0, blue = 100, alpha = 200)

And output the value in Red, Green, Blue, Alpha format.

I am expecting an output as follows (the greenish central color):

enter image description here

Thanks so much for helping this foolish coder!

Upvotes: 2

Views: 742

Answers (1)

user1148358
user1148358

Reputation:

Like most questions, one ends up answering it one self:

public static int MergeColors(int backgroundColor, int foregroundColor) {
    final byte ALPHA_CHANNEL = 24;
    final byte RED_CHANNEL   = 16;
    final byte GREEN_CHANNEL =  8;
    final byte BLUE_CHANNEL  =  0;

    final double ap1 = (double)(backgroundColor >> ALPHA_CHANNEL & 0xff) / 255d;
    final double ap2 = (double)(foregroundColor >> ALPHA_CHANNEL & 0xff) / 255d;
    final double ap = ap2 + (ap1 * (1 - ap2));

    final double amount1 = (ap1 * (1 - ap2)) / ap;
    final double amount2 = amount1 / ap;

    int a = ((int)(ap * 255d)) & 0xff;

    int r = ((int)(((float)(backgroundColor >> RED_CHANNEL & 0xff )*amount1) +
            ((float)(foregroundColor >> RED_CHANNEL & 0xff )*amount2))) & 0xff;
    int g = ((int)(((float)(backgroundColor >> GREEN_CHANNEL & 0xff )*amount1) +
            ((float)(foregroundColor >> GREEN_CHANNEL & 0xff )*amount2))) & 0xff;
    int b = ((int)(((float)(backgroundColor & 0xff )*amount1) +
            ((float)(foregroundColor & 0xff )*amount2))) & 0xff;

    return a << ALPHA_CHANNEL | r << RED_CHANNEL | g << GREEN_CHANNEL | b << BLUE_CHANNEL;
}

Source: Color mixing in android

Upvotes: 1

Related Questions