Pegtop delphi

color burn mode

Description:
This mode is some kind of inverted screen mode (the multiplication is replaced by a division of the "inverse").

Formula:
f(a,b) = 1 - (1 - a) / b



Disadvantage:
The formula can result in values smaller than 0, so some truncation can occur.

Code:
if b = 0 then result := 0 else begin c := 255 - (((255-a) SHL 8) DIV b); if c < 0 then result := 0 else result := c; end;

inverse color burn mode

Description:
I've never seen this mode anywhere, probably because it is the same than color burn mode, but base color and blend color are swapped (diagram 2 equals "flipped screen mode").

Formula:
f(a,b) = 1 - (1 - b) / a



Disadvantage:
The formula can result in values smaller than 0, so some truncation can occur.

Code:
if a = 0 then result := 0 else begin c := 255 - (((255-b) SHL 8) DIV a); if c < 0 then result := 0 else result := c; end;

soft burn mode

Description:
This mode is a combination of color burn and inverse color dodge mode, but a lot smoother than both of them. The base image is lightened a bit, but very dark blend colors are "burned" in. I chose this name, because my aim was to make the color burn mode softer.

Formula:



Disadvantages:
The formula can result in values smaller than 0 or greater than 255, so some truncation can occur (but not as extreme as for color burn).
There are two separate formulas (but no real discontinuance).

Code:
if a+b < 256 then begin if a = 255 then Result := 255 else begin c := (b SHL 7) DIV (255-a); if c > 255 then Result := 255 else Result := c; end; end else begin // b cannot be zero here c := 255-(((255-a) SHL 7) DIV b); if c < 0 then Result := 0 else Result := c; end;

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