programming layer blend modes
Hi I am programming the pin light blend mode found in photoshop. What the transfer mode does is pretty much compare 2 pixels and keep the darker one.
Im not sure how to convert and compare vectors with scalars
This is the algorithm:
A - foreground RGB
B - background RGB
C - composite RGB vectors
tonal values are normalized as such
1 = 255/255 ...scalar
There are three conditional statements in the algorithm
if(B < 2 * A - 1)
{
C = 2 * A - 1;// the 1 in the equation is throwing me off
}
else if ( ( B > 2 * A - 1 ) && ( B < 2 * A ) )
{
C = B;
}
else if ( B > 2 * A )
{
C = 2 * A;
}
How do I convert RGB values, which are vectors, to tonal values which are scalars?
2 * vector gives you a result vector. How do I subtract 1 from a result vector? Do I subtract 1 from each element or from the magnitude of the result vector?... I'm not sure. or is 1 the magnitude of the vector which has to be subtracted from the result vector.
The second statement compares which vector is greater ( B < 2*A ). Is it comparing the magnitudes of the vectors?
Please help
Nikos
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