So for anyone looking into old school graphics programming, bit planes are pretty confusing when you don't understand why they exist.
Two big reasons. First, it's about running memory chips in parallel to increase bandwidth. Image data was hard to get to the screen fast enough with hardware in that era.
Second it allowed for simple backwards compatibility. Programs were used to writing directly to video memory, and in an EGA card the start of the video memory was valid CGA data. The rest of the colour data was in a separate bit plane.
This brought back some memories. So nice to see art from an era where you really needed talent to be able to produce it. Such a nice contrast to the AI slop which takes no talent to produce!
Color cycling in the picture file format was so epic!
Fun memory: I was with my best friend at another friend's place and his father called him to do some chore. He had to quickly mow the small lawn or something like that. So we decided to prank him: I don't remember all the details but basically we launched Deluxe Paint and simulated an Amiga "guru meditation" using a font that wasn't even correct (I think because we were in 320x256 while the real guru meditation was using a mode with smaller pixels). Then in broken english we wrote something like this:
"Hardware failure. If you reboot or turn off your computer it is going to broke forever"
We then did a color cycling between red and black for one of the color and put the drawing software in "full screen".
When our friend came back, we played dumb and said we had no idea what happened but that apparently we really shouldn't turn the computer off. We managed to hold it for something like ten minutes while he though his computer was done for good but we were dying inside.
P.S: as a side note with the help of Claude Code CLI / Sonnet 4.6 I managed to recompile a 30+ years old game I wrote in DOS in the early 90s (and for which I still have the source files and assets but not the tooling) and I was using converter (which I wrote back then) to convert files between the .LBM format and a "tweaked" (320x200 / 4 planes) DOS mode I was using for the game (which allowed double-buffering without tearing). I don't remember the details but I take it that if we had .LBM picture files, me and the artist where using Deluxe Paint on the Amiga.
Two big reasons. First, it's about running memory chips in parallel to increase bandwidth. Image data was hard to get to the screen fast enough with hardware in that era.
Second it allowed for simple backwards compatibility. Programs were used to writing directly to video memory, and in an EGA card the start of the video memory was valid CGA data. The rest of the colour data was in a separate bit plane.
Fun memory: I was with my best friend at another friend's place and his father called him to do some chore. He had to quickly mow the small lawn or something like that. So we decided to prank him: I don't remember all the details but basically we launched Deluxe Paint and simulated an Amiga "guru meditation" using a font that wasn't even correct (I think because we were in 320x256 while the real guru meditation was using a mode with smaller pixels). Then in broken english we wrote something like this:
"Hardware failure. If you reboot or turn off your computer it is going to broke forever"
We then did a color cycling between red and black for one of the color and put the drawing software in "full screen".
When our friend came back, we played dumb and said we had no idea what happened but that apparently we really shouldn't turn the computer off. We managed to hold it for something like ten minutes while he though his computer was done for good but we were dying inside.
All three of us remember that prank to this day.
https://en.wikipedia.org/wiki/Guru_Meditation
P.S: as a side note with the help of Claude Code CLI / Sonnet 4.6 I managed to recompile a 30+ years old game I wrote in DOS in the early 90s (and for which I still have the source files and assets but not the tooling) and I was using converter (which I wrote back then) to convert files between the .LBM format and a "tweaked" (320x200 / 4 planes) DOS mode I was using for the game (which allowed double-buffering without tearing). I don't remember the details but I take it that if we had .LBM picture files, me and the artist where using Deluxe Paint on the Amiga.