OpenGL extension EXT.blend_subtract
This module customises the behaviour of the OpenGL.raw.GL.EXT.blend_subtract to provide a more Python-friendly API
Overview (from the spec)
Two additional blending equations are specified using the interface defined by EXT_blend_minmax. These equations are similar to the default blending equation, but produce the difference of its left and right hand sides, rather than the sum. Image differences are useful in many image processing applications.
The official definition of this extension is available here:
Return boolean indicating whether this extension is available