Back in 1985 when the Amiga was first released, the HAM (Hold And Modify) screenmode was revolutionary. It allowed 4096 colours to be displayed simultaneously, meaning near true-colour images could be displayed while only using the amount of memory that a normal 64-colour screen would use.<\/p>\n
HAM does have its disadvantages, though – while a regular bitplane image can be faded out very easily by simply fading the palette, this trick doesn’t work for HAM images.<\/p>\n
Fading out a HAM image can be done, however, using the Blitter.<\/p>\n
This AMOSPro program uses some “evil” trickery to fade a HAM image to black, using the Screen Copy command with blitter modes, peeks and pokes to shuffle bitplanes around between screens, and what amounts to a ShadeBOB routine over the entire screen.<\/p>\n
Step by step, the theory of operation is something like this:<\/p>\n
This is done simultaneously with fading out the palette, and the end result is quite a nice fade-out of a HAM image.<\/p>\n
Download: Compiled HAM fading slideshow, including AMOSPro source code<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Back in 1985 when the Amiga was first released, the HAM (Hold And Modify) screenmode was revolutionary. It allowed 4096 colours to be displayed simultaneously, meaning near true-colour images could be displayed while only using the amount of memory that … Continue reading