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delphi section   articles   blend modes   introduction   normal mode   average mode   multiply mode   screen mode   darken mode   lighten mode   difference modes   overlay mode   hard light mode   soft light mode   dodge modes   burn modes   quadratic modes   additive modes   interpolation mode   logical modes   RGB modes   HSL modes   opacity   dark modes   bright modes   final words   components   about me	color dodge mode Description: This mode is some kind of inverted multiply mode (the multiplication is replaced by a division of the "inverse"). Formula: f(a,b) = a / (1 - b) Disadvantage: The formula can result in values greater than 1, so some truncation can occur. Code: if b = 255 then result := 255 else begin c := (a SHL 8) DIV (255-b); if c > 255 then result := 255 else result := c; end; inverse color dodge mode Description: I've never seen this mode anywhere, probably because it is the same than color dodge mode, but base color and blend color are swapped (diagram 2 equals "flipped multiply mode"). Formula: f(a,b) = b / (1 - a) Disadvantage: The formula can result in values greater than 1, so some truncation can occur. Code: if a = 255 then result := 255 else begin c := (b SHL 8) DIV (255-a); if c > 255 then result := 255 else result := c; end; soft dodge mode Description: This mode is a combination of color dodge and inverse color burn mode, but a lot smoother than both of them. The base image is darkened a bit, but very bright blend colors are "dodged" in. I chose this name, because my aim was to make the color dodge mode softer. Formula: f(a,b) =  ½a / (1 - b) (for a + b < 1) 1 - ½(1 - b) / a (else) 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 dodge). There are two separate formulas (but no real discontinuance). Code: if a + b < 256 then begin if b = 255 then result := 255 else begin c := (a SHL 7) DIV (255-b); if c > 255 then result := 255 else result := c; end; end else begin // a cannot be zero here c := 255 - (((255-b) SHL 7) DIV a); if c < 0 then result := 0 else result := c; end; index | previous page | next page
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