VIC20 Picture Converter/Viewer

See also: C64Gfx
And Also: More Examples by Anders Carlsson

Features

• Software-assisted mode (color multiplex)
• 100 x 160 pixel (25 x 10 character) multicolor resolution (width x height)
• Max 16 colors
• 25 x 20 character color memory resolution
• each line can have 3 selectable colors in addition to color memory
• Creates either raw graphics files or VIC20 executables
• Supports PAL and NTSC, 8k and 3k memory expansions
• Hires mode support (-H).

Introduction

I then coded some demo parts for VIC20. Some ideas were conversions from my C64 demos and I guess from there arose also the idea of a sort of FLI for VIC. VIC-I does not have a graphics mode and thus all graphics must be created with user-definable characters. The pixel resulution is awful, but the color resolution is even worse, because the whole screen shares three of the four multicolor colors. In addition, the 16x8-character mode causes each color cell to define the character color for a 16x4-pixel area.

The graphics viewer increases the color resolution considerably by multiplexing the three multicolor colors (in VIC20 they are located in the border+background and auxiliary color registers), which gives three selectable colors for each rasterline. In addition, both color memory halves are used and they are switched every eight lines, doubling the color memory resolution.

Yet another problem is that only colors 0-7 can be used freely. Colors 8-15 can only be used as auxiliary or background color. Fortunately only two of the colors 8-15 are actually usable, the other 6 are only lighter versions of the colors in the 0-7 range.

The graphics converter reads in a PPM-format picture, performs color quantization and dithering, performs color selection and actual conversion, then writes the results into a file, optionally with a viewer program attached so you can simply load and run the file in VIC20.

My three VIC20 demo parts still wait for good music, but here is the picture converter. Releasing it doesn't stop me from using it to create a graphics part for a demo later on.

And now it is later, so visit Vici Iterum MM and get your copy.

Usage

Usage: ppmtovic [-<options>] [ppmfile [vicfile]]
       d<n> = do a simple dither in the color conversion (1-n)
       l<n> = the importance of luminance in color conversion (0..20), default 7
       b<n> = brighten or darken the picture (-255..255), default 0
       c<n> = increase the contrast (-100..100 [0%..200%), default 0
       v = verbose, output extra information about the process
       q = quiet, no progress output
       o = optimize color selection (mean average error)
       i<colmem/hi/lo/back> = initialize colors (e.g. -i0/8/9/7)
       u1111111110000000 = use colors (default shown)
       p = insert a PAL viewer (8k exp. by default)
       n = insert an NTSC viewer (8k exp. by default)
       3 = use viewer for 3k expansion
       H = hires mode

Using the -u option you can select which colors will be used in the conversion. The default is to use colors 0-8, but you very often get better pictures if you don't use red (2) in the conversion. ppmtovic -u1101011111000 -d1 07.ppm 07.v will use the colors black, white, cyan, green, blue, yellow, orange, and light orange in the conversion. This leaves out red, purple, and colors 10-15.

The converter also allows you to give higher importance to the resulting luminance values instead of the right color. For "non-realistic" pictures a higher luminance importance (e.g. -l11) usually gives better results.

  0   black
  1   white
  2   red
  3   cyan
  4   purple
  5   green
  6   blue
  7   yellow
  8   orange
  9   light orange
 10   pink
 11   light cyan
 12   light purple
 13   light green
 14   light blue
 15   light yellow

Hires mode is selected with -H. In this mode border and auxiliary colors in -i are ignored. If only two colors are selected in -u, one of them is used as the background color automatically. More than three enabled colors rarely give good results. For example ppmtovic -H -d1 -u0110000000100000 -c40 -b-10 tmp2.ppm tmp.pic creates a raw graphics file in hires mode with white, red, and light red.

victoppm converts the raw graphics files (saved without a viewer) back to PPM files. Multicolor and hires mode is automatically detected.

Examples

Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Get PAL Get NTSC
Hires-mode example
Hires-mode example
Hires-mode example
Hires-mode example

loader.pal loader.ntsc graphics D64 PAL and NTSC: unexpanded.d64.gz

For 3kB RAM expansion: 14-pal.3k 14-ntsc.3k