There's no "reverse" on _MEMNEW. Once you use it, it's manual handling of that block from that point on.
The easiest way to do what you're suggesting is:
handle = _MEMNEW... sizes as needed
DIM tempM AS _mem
tempM = _MEMIMAGE(handle)
then just _MEMCOPY the memnew block to the tempM which points to the image.
Images hold a lot more info than you think. Length, height, bits per pixel, palette, font, blend on/off, print cursor x/y info, current background/foreground colors.... lots of stuff that a memnew block wouldn't track at all.
The easiest way to do what you're suggesting is:
handle = _MEMNEW... sizes as needed
DIM tempM AS _mem
tempM = _MEMIMAGE(handle)
then just _MEMCOPY the memnew block to the tempM which points to the image.
Images hold a lot more info than you think. Length, height, bits per pixel, palette, font, blend on/off, print cursor x/y info, current background/foreground colors.... lots of stuff that a memnew block wouldn't track at all.