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I would like to do 2 things:

  1. Compare two colors (RGB), so that comparer gives me say 1 if the colors are the same and 0 if the compared colors are on the opposite sides of RGB like black and white, and some number from 0 to 1 if they are somehow equal (like both are reddish)
  2. Mix 2 or more colors together to produce a new one: mixing blue and yellow should give me green, mixing red and green should give black etc.

Questions: Is there any parts of java API which can do something like this for me? If not is there any 3rd part open source java libraries which can facilitate that?

Thanks.

BanditoBunny
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    Have you looked at: http://stackoverflow.com/questions/9018016/how-to-compare-two-colors ? – condit Sep 12 '12 at 22:45
  • Thanks, I have seen that, it looks complicated, I don't have the time right now to try to understand it. – BanditoBunny Sep 12 '12 at 22:47
  • Color distance metrics are usually complex. You can cheat (if accuracy isn't a big deal) by doing something like *1 - A/B*. – obataku Sep 12 '12 at 23:01
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    There's an algorithm in Java for your first request in the answers to http://stackoverflow.com/q/2103368/53614 You would just need to scale the results to be between 1 and 0 – barrowc Sep 12 '12 at 23:03

1 Answers1

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1.

There are many different methods for comparing colors. If you want perceptual dissimilarity, check out the comments of other users. If you just want something simple that gives an indication: use this code:

int rgb1 = ...
int rgb2 = ...
int r, g, b;

r = (rgb1 >> 16) & 0x000000ff;
g = (rgb1 >> 8) & 0x000000ff;
b = rgb1 & 0x000000ff;

r -= (rgb2 >> 16) & 0x000000ff;
g -= (rgb2 >> 8) & 0x000000ff;
b -= rgb2 & 0x000000ff;

double answer = (r*r+g*g+b*b)/(255*255*3.0);

It calculates a euclidean distance and scales it to range from 0 to 1.

2.

Just as there are many different ways to compare colors, there are many ways to combine colors. It depends on what you want. You could take the average but that's not what you want. As it would darken the resulting color.

EDIT: here is the code to take the average:

r = (rgb1 >> 16) & 0x000000ff;
g = (rgb1 >> 8) & 0x000000ff;
b = rgb1 & 0x000000ff;

r += (rgb2 >> 16) & 0x000000ff;
g += (rgb2 >> 8) & 0x000000ff;
b += rgb2 & 0x000000ff;

int average = ((r/2)<<16)+((g/2)<<8)+(b/2);

If you are somewhat mathematically inclined think about what behavior you actually look for, and try to put it in a formula (or rather 3 formulas, one for red, one for green, and one for blue) It shouldn't be hard to convert the formula to java code.

You can put individual r, g and b values back into a single rgb value using

int rgb = (r<<16) | (g<<8) | b

Edit: notice that computers work with `red GREEN blue´, where yellow is a combination of green and blue, not the other way around. Conversion can be done, but I have not done it yet. Perhaps conversion between rgb and ryb color spaces may be of help.

Community
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neXus
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  • Thanks for you answer, if I had the formula. I will try first to take an avg of each color separately and see what happens. – BanditoBunny Sep 13 '12 at 21:06
  • Also: working with `java.awt.Color´ might make your code easier to read... int r = color.getRed(); int g = color.getGreen(); int b = color.getBlue(); new Color(r,g,b); – neXus Sep 22 '12 at 15:20