ppmtovic - VIC20 pictures

The Commodore VIC-20 home computer (1980-1985) got its name from the Video Interface Chip, a combined graphics and sound chip. The chip can generate 16 colours, but for high resolution pictures the palette was restricted to background and one of eight colours for every cell of 4x8 pixels, plus in multi colour mode you could use two extra colours which were the same for the whole screen.

About 20 years later, Pasi 'Albert' Ojala developed ppmtovic, a picture generator and viewer which uses exact timing to select the other three colours once every raster line. Read more about the software on VIC20Gfx page. Albert also developed a tool that generates an IFF ILBM picture back from the rendered program. As this tool only would compile on an Amiga, I rewrote it to generate a new PPM file instead - download the single-file source code in victoppm.c.

Here are a number of pictures I've converted. In some cases, the parameters and an executable file are available. The output GIFs could easily be converted back to VIC-20 format just by selecting the right palette.

NEWS! (November 16, 2008) Download Windows executables here:

• ppmtovic = converts a PPM file to VIC-20 executable
• victoppm = converts back the VIC file to PPM for preview how it will look like

	This is a resized (and re-aspected) version of the Lenna picture. This is the third conversion, and compared to earlier results, this one has fewer square artifacts and more dark areas. Parameters: -l2 -b-18 -c75 -o -u1110001111100011 (download +8K PAL VIC program)
	This saxophone picture was resized and rotated 90 degrees counter-clockwise. On the third conversion without "-d", the golden shades on the saxophone doesn't display themselves too good. Grmbl. Parameters: -l2 -b-25 -c100 -o -u1110010110000101 (download +8K PAL VIC program)
	This cartoonish picture is from a COMPUTE! issue, illustrating a typical Basic game listing for a dozen home computers, including the VIC-20. The result on second conversion attempt is not quite as colourful as on the first try, but much closer to the original picture. Parameters: -l2 -b-25 -c100 -o -u1101011111110111 (download +8K PAL VIC program)
	This picture of an exotic island was downloaded from Webshots and was chosen due to the few red tones. The leaves are a little too dark, and the sky a little too greenish, but otherwise I'm quite satisfied. This was the first screen shot generated with victoppm. Parameters: -l1 -b-25 -c100 -o -u1100011000010111 (download +8K PAL VIC program)
	A pair of tigers, again from Webshots. The colour palette mainly contains orange, black, white and blue. Grrrmiaow. Parameters: -l3 -b-25 -c100 -o -u1100001011000011 (download +8K PAL VIC program)
	This was cut out from a digital camera test picture taken by ceder. The picture as a whole was colourful, but didn't quite have the proportions to be used here. I'm utilizing as many of the brighter colours as possible. Isn't it amazing how I almost always end up with 200% contrast on these pictures? Parameters: -l4 -b25 -c100 -o -u110101111101111 (download +8K PAL VIC program)
	Alfred E. Newman, from some web page.
	Alien Landing, by Conny Larsson.
	CZE-RUS in WC 2002 (Sweden).
	Pulp Fiction, from a C64 demo.
	Mount Shuksan, from www.webshots.com.
	Spite, by Conny Larsson.
	Teenage Mutant Hero Turtles, from C64 game.
	The Illusion of Truth - Sheridan plays with model.
	Yeah, yeah, yeah... DOOM is here. Sorry, no downloadable game, only an awfully converted screenshot.