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Index › Programming Questions & Help › Syntax Questions › Color blending not blending properly
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Color blending not blending properly (Read 416 times)
4dplane
Color blending not blending properly
Mar 31st, 2006, 3:57am  
color c1 = color(0,0,127);
color c2 = color(0,0,127);
color c3 = blend(c1, c2, ADD);
color c4 = color(0,0,255);

print("c3="+c3+"\n");
print("c4="+c4+"\n");

These are the prints I get:

c3=-16776963
c4=-16776961

Why are these numbers not the same and why are they negative?
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adzer2
Re: Color blending not blending properly
Reply #1 - Mar 31st, 2006, 5:37am  
Why dont you add the two values in c1 and c2 before putting them into c3?

I have no idea why c4 is like that, is there more code than this?
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4dplane
Re: Color blending not blending properly
Reply #2 - Mar 31st, 2006, 7:37am  
The code I posted is just an example to show what problems I am having with color blend ADD method. If this problem could be explained I should be able to solve the problem I am having in my project.
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JohnG
Re: Color blending not blending properly
Reply #3 - Mar 31st, 2006, 11:11am  
127+127 == 254 not 255...
However, the blend function seems to be making the blue component of c3 253 instead of 254.

The reason they're negative is that colour is just a single 32 bit int, with 8 bits each for alpha, red, green and blue, so printing it treats it as a single value, not 4 component values.

This function will print the values of a color nicely:
Quote:
void colorPrint(color c)
{
 int a=((c&0xFF000000)>>24)&0x000000FF;
 int r=(c&0x00FF0000)>>16;
 int g=(c&0x0000FF00)>>8;
 int b=(c&0x000000FF);
 println("Color("+r+","+g+","+b+","+a+")");
}
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4dplane
Re: Color blending not blending properly
Reply #4 - Mar 31st, 2006, 10:35pm  
Thanks for the print function. It appears that when ever blending two colors that are odd the new color will be 1 less then it should be.

This problem enlarges when adding more colors together:

color c1 = color(0,0,5);
color c2 = color(0,0,5);
color c4 = color(0,0,5);
color c3 = blend(c1, c2, ADD);
color c5 = blend(c3, c4, ADD);

void setup() {
 colorPrint(c5);
}
void colorPrint(color c){
 int a=((c&0xFF000000)>>24)&0x000000FF;
 int r=(c&0x00FF0000)>>16;
 int g=(c&0x0000FF00)>>8;
 int b=(c&0x000000FF);
 println("Color("+r+","+g+","+b+","+a+")");
}

The print = Color(0,0,13,255)

This appears to be the problem I am having - when I add colors over and over again, in time, the new color goes to black.
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