The Minmax Blending Extension

The Minmax Blending Extension

The minmax blending extension, EXT_blend_minmax, extends blending capability by introducing two new equations that produce the minimum or maximum color components of the source and destination colors. Taking the maximum is useful for applications such as maximum projection in medical imaging.

This extension also introduces a mechanism for defining alternate blend equations. Note that even if the minmax blending extension is not supported on a given system, that system may still support the logical operation blending extension or the subtract blending extension. When these extensions are supported, the glBlendEquationEXT() function is also supported.

Using a Blend Equation

To specify a blend equation, call glBlendEquationEXT():

void glBlendEquationEXT(GLenum mode)

The mode parameter specifies how source and destination colors are combined. The blend equations GL_MIN_EXT, GL_MAX_EXT, and GL_LOGIC_OP_EXT use source or destination factors.

If mode is set to GL_FUNC_ADD_EXT, then the blend equation is set to GL_ADD, the equation used currently in OpenGL 1.0. The glBlendEquationEXT() reference page lists other modes. These modes are also discussed in "The Blend Subtract Extension" and "The Logical Operation Blending Extension". While OpenGL 1.0 defines logic operation only on color indices, this extension extends the logic operation to RGBA pixel groups. The operation is applied to each component separately.

New Functions

glBlendEquationEXT()