status = image:SetColorMask(rmin, rmax, gmin, gmax, bmin, bmax)
image:SetColorMask()
sets the transparent color of the image by the RGB range values.
The color within the range is displayed as a transparent color.
The image must be in RGB color space.
#HPDF_INVALID_IMAGE
- An invalid image handle was set.
#HPDF_INVALID_COLOR_SPACE
- An image other than RGB color was specified.
#HPDF_FAILED_TO_ALLOC_MEM
- Memory allocation failed.
#HPDF_INVALID_PARAMETER
- An invalid value is specified.