modes

Blend modes (or mixing modes) in digital image editing and computer graphics are used to determine how two layers are blended with each other. The default blend mode in most applications is simply to obscure the lower layer by covering it with whatever is present in the top layer (see alpha compositing). However, as each pixel has a numerical representation, there exist a large number of ways to blend two layers.
Most graphics editing programs like Adobe Photoshop and GIMP allow the user to modify the basic blend modes, e.g. by applying different levels of opacity to the top "layer". The top "layer" is not necessarily a layer in the application; it may be applied with a painting or editing tool. The top "layer" can also be referred to as the "blend layer" or "active layer".
In the formulas shown on this page, values go from 0.0 (black) to 1.0 (white).

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