Fred4 supports the following blending methods:

•Opacity - Standard color transparency:

Mix source and backdrop color using defined opacity level (0-100, used only for this method).

•Multiply - Multiplies the backdrop and source color values:

The result color is always at least as dark as either of the two constituent colors.

Multiplying any color with black produces black; multiplying with white leaves the original color unchanged.

Painting successive overlapping objects with a color other than black or white produces progressively darker colors.

•Screen - Multiplies the complements of the backdrop and source color values, then complements the result:

The result color is always at least as light as either of the two constituent colors.

Screening any color with white produces white; screening with black leaves the original color unchanged.

The effect is similar to projecting multiple photographic slides simultaneously onto a single screen.

•Darken - Selects the darker of the backdrop and source colors:

The backdrop is replaced with the source where the source is darker; otherwise, it is left unchanged.

•Lighten - Selects the lighter of the backdrop and source colors:

The backdrop is replaced with the source where the source is lighter; otherwise, it is left unchanged.

•Difference - Subtracts the darker of the two constituent colors from the lighter color:

Painting with white inverts the backdrop color; painting with black produces no change.