Blending Modes
What they are and how to use them.
Compositing is the process of taking one or more layers and putting them together into a single image. This is what Acorn does when it draws multiple layers on top of each other, forming a single image in its canvas. Acorn also gives you the ability to decide how each layer is to be drawn, which is known as it's "blend mode". Most of the time, you'll probably have a layer's blend mode set to "Normal". However, sometimes you'll want to change it depending on what you want your image to look like.
To change a layer's blend mode, select the layer you want to change in the layers list, and choose an option from the Blending menu:
Acorn's Various Blending Modes and Their Descriptions
Here are two images. My dogs Jimi and Stevie Ray, and an image with a gradient and various colors in it. The pups will be the bottom layer for our examples, and the second image will be our top layer. We'll be adjusting the blend modes for the top layer.
Note: These descriptions are taken from Apple's Quartz 2D Programming Guide.
Normal
This one is pretty self explanatory, and is the default blend mode for new layers. Acorn draws the layer on top of any layers below it, without any specific blending tricks.
Darker
The Darker blend mode works by drawing whichever pixels are darker- the top layer or the bottom layer.
Lighter
The opposite of Darker, the Lighter blend mode draws whichever parts are lighter
Multiply
Multiply blend mode multiplies the top image with bottom image.
Color Dodge
Color Dodge will brighten the bottom image over the top image.
Color Burn
Color Burn will darken the bottom image over the top image
Hard Light
"Hard light blend mode either multiplies or screens colors, depending on the source image sample color. If the source image sample color is lighter than 50% gray, the background is lightened, similar to screening. If the source image sample color is darker than 50% gray, the background is darkened, similar to multiplying"
Soft Light
Soft light blend mode either darkens or lightens colors, depending on the source image sample color. If the source image sample color is lighter than 50% gray, the background lightens, similar to dodging. If the source image sample color is darker than 50% gray, the background darkens, similar to burning.
Overlay
"Overlay blend mode either multiplies or screens the source image samples with the background image samples, depending on the color of the background samples. The result is to overlay the existing image samples while preserving the highlights and shadows of the background. The background color mixes with the source image to reflect the lightness or darkness of the background."
Screen
Screen blend mode multiplies the inverse of the source image samples with the inverse of the background image samples to obtain colors that are at least as light as either of the two contributing sample colors.
Difference
Difference blend mode subtracts either the source image sample color from the background image sample color, or the reverse, depending on which sample has the greater brightness value. Source image sample values that are black produce no change; white inverts the background color values.
Exclusion
Exclusion blend mode produces a lower-contrast version of the difference blend mode. Source image sample values that are black don’t produce a change; white inverts the background color values.
Hue
Hue blend mode uses the luminance and saturation values of the background with the hue of the source image.
Saturation
Saturation blend mode uses the luminance and hue values of the background with the saturation of the source image. Pure gray areas don’t produce a change.
Color
Color blend mode uses the luminance values of the background with the hue and saturation values of the source image. This mode preserves the gray levels in the image.
Luminosity
Luminosity blend mode uses the hue and saturation of the background with the luminance of the source image to creates an effect that is inverse to the effect created by the color blend mode.
