Linear light layer mode is a combination of addition and linear burn.
Algorithm:
If upper layer component<=50% -> apply linear burn.
If upper layer component>=50% -> apply addition.
Apply this calculation to R,G,B components respectively to each pixel.
If you draw a graph to show the relation of input-output values, linear light looks like a linear function in mathematics (unlike other combination modes such as hard light and vivid light). Hence it gets this name.
For example, fix lower layer at 35% and draw a graph about upper layer and blended color.
Names and algorithms of these layer modes come from Photoshop. Because many drawing softwares implement their layer modes based on Photoshop's, including these modes in GIMP can make drawing techniques compatible with other softwares.
EDIT : I made a mistake. Update the graph.
Algorithm:
If upper layer component<=50% -> apply linear burn.
If upper layer component>=50% -> apply addition.
Apply this calculation to R,G,B components respectively to each pixel.
If you draw a graph to show the relation of input-output values, linear light looks like a linear function in mathematics (unlike other combination modes such as hard light and vivid light). Hence it gets this name.
For example, fix lower layer at 35% and draw a graph about upper layer and blended color.
Names and algorithms of these layer modes come from Photoshop. Because many drawing softwares implement their layer modes based on Photoshop's, including these modes in GIMP can make drawing techniques compatible with other softwares.
EDIT : I made a mistake. Update the graph.