The Logo Color Key values determine a color range that is treated as transparent. Any logo pixel that falls in this range are not blended on top of the underlying layer but is transparent. This equation is used to determine if a pixel is transparent.
Let ( r, g, b ) be a pixel value of the logo.
Let ( min_r, min_g, min_b ) and ( max_r, max_g, max_b ) be the values of the Color Key registers.
Then, pixel ( r, g, b ) is transparent if the following holds:
min_r ≤ r ≤ max_r AND
min_g ≤ g ≤ max_g AND
min_b ≤ b ≤ max_b
To turn off background color keying, program a maximum value that is smaller than the minimum value, for example, maximum is 0, minimum is 1.