The ink modifies the way the active tool paints. The default ink is the Simple Ink.
It acts in the following way:
- If the foreground color is opaque (alpha = 255 = 100%), it paints with the given opaque color.
- If the color has alpha (0 < alpha < 255), it composite the color with the layer surface.
- If the color is transparent (alpha = 0, Mask color), the tool acts like an Eraser.
It merges the foreground color with the layer surface depending on the alpha value of the foreground color:
- If alpha = 255 = 100%, the foreground color will be completely opaque.
- If alpha = 128 = 50%, the foreground color is merged 50% with the layer surface color.
- If alpha = 0 = 0%, the painting has no effect because the color is completely transparent.
It replaces the layer surface pixels with the active foreground color with its alpha value. It doesn't make any kind of alpha compositing, it just takes the active color and put it exactly as it is in the destination pixel.
E.g. In this case, if alpha = 128 = 50%, the final color will be the same as the foreground color with alpha = 128, ignoring the layer surface.
In this case the original alpha values from the layer surface are kept, and only the RGB color components are replaced from the foreground color.
See the shading section for more information about this special ink for pixel-art.