Blend two images using an alpha channel = [a * alpha + b * (1 - alpha)]. \n
* Can be done in-place, images must match. \n
* alpha_image must have the same data type except for complex images that must be real,
* and color_space must be IM_GRAY.
* Maximum alpha values are based in \ref imColorMax. Minimum is always 0.
* \verbatim im.ProcessBlend(src_image1: imImage, src_image2: imImage, alpha_image: imImage, dst_image: imImage) [in Lua 5] \endverbatim
* \verbatim im.ProcessBlendNew(image1: imImage, image2: imImage, alpha_image: imImage) -> new_image: imImage [in Lua 5] \endverbatim
* \ingroup arithm
Blend two images using an alpha channel = [a * alpha + b * (1 - alpha)]. \n * Can be done in-place, images must match. \n * alpha_image must have the same data type except for complex images that must be real, * and color_space must be IM_GRAY. * Maximum alpha values are based in \ref imColorMax. Minimum is always 0. * \verbatim im.ProcessBlend(src_image1: imImage, src_image2: imImage, alpha_image: imImage, dst_image: imImage) [in Lua 5] \endverbatim * \verbatim im.ProcessBlendNew(image1: imImage, image2: imImage, alpha_image: imImage) -> new_image: imImage [in Lua 5] \endverbatim * \ingroup arithm