Setting alpha value

igor_odriozola

I see that with the alpha() function we can extract the alpha value of a color. But is there a way to set this value without using fill? I would like to set the alpha value to an unknown color.

calsign

If I understand your question correctly, you can do something like this:

//Red, no alpha
color c = color(255, 0, 0);

//Change the alpha (not the most elegant, perhaps...)
c = color(red(c), green(c), blue(c), 127);

There is also a way to do this by shifting bits, but I don't know how to do that off of the top of my head...

GoToLoop

//forum.processing.org/two/discussion/4617/setting-alpha-value

background(#0080A0);

loadPixels();
color c = pixels[0];
println(hex(c));              // pixel color

color a = c >>> 030;
println(hex(a, 2));           // extracted alpha octet
println(hex(a >>= 1, 2));     // half of alpha

println(hex(c &= 0xFFFFFF));  // clear alpha octet
println(hex(c |= a << 030));  // reinserts modified alpha

updatePixels();
exit();