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Index › Programming Questions & Help › Syntax Questions › Easiest way to add alpha value to colour
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Easiest way to add alpha value to colour? (Read 576 times)
tiefblau
Easiest way to add alpha value to colour?
Oct 3rd, 2007, 10:44pm  
Hello!

What is the simplest and fastest way to add an alpha value to a RGB colour?

At the moment I'm extracting the red, green and blue values from the old colour and put them together again with an alpha value. I'd like to simply add an alpha to the whole rgb colour value, but don't know how. =/

Thanks for your help.
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steven
Re: Easiest way to add alpha value to colour?
Reply #1 - Oct 3rd, 2007, 10:53pm  
Hi,

I'm not quite sure I understand your request but from what I understand can't you just add the alpha in the fill statement

For example : fill(r,g,b,alpha)

If this is not what you're looking for, could you please give more explanation.

Thanks
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tiefblau
Re: Easiest way to add alpha value to colour?
Reply #2 - Oct 3rd, 2007, 11:14pm  
I'm reading rgb colour values from the pixels[] array. Now I want to add alpha to those values, without pulling apart the rgb values if possible.

At the moment I'm doing something like this (adding alpha of 100 to some colour):

Code:
newColour = 100 << 24 | (oldColour >> 16 & 0xFF) << 16 | (oldColour >> 8 & 0xFF) << 8 | oldColour & 0xFF;


I'd like to skip the part of getting the single red, green and blue values from a colour and rather do something simple like rgb + alpha = new colour. But I don't know how.
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JohnG
Re: Easiest way to add alpha value to colour?
Reply #3 - Oct 3rd, 2007, 11:27pm  
newcolor=(oldcolor&0x00FFFFFF)+0x60000000;
or if you don't know the hex value for the alpha, you can do:
newcolor=(oldcolor&0x00FFFFFF)+(100<<24);
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tiefblau
Re: Easiest way to add alpha value to colour?
Reply #4 - Oct 3rd, 2007, 11:39pm  
Yes, that's much better! ^^

Thanks for your replies JohnG and steven.
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