int im_rad2float( IMAGE *in, IMAGE *out )
int im_float2rad( IMAGE *in, IMAGE *out )
im_rad2float(3) unpacks a 4-band uchar image in IM_CODING_RAD format to 3-band float. RAD images are used by the radiance(1) family of programs for HDR imaging.
Some VIPS operations will work directly on the packed RAD images (such as im_extract_area(3) ) but many will require the image to be unpacked to 3-band float for processing.
im_float2rad(3) packs a 3-band float image back to 4-band uchar in IM_CODING_RAD format.