Graphics Files on Linux

Note: I haven't tested any of this stuff out yet, it's all from online documentation. I want to play with the pnm/pbm/ppm stuff a little more and explain how they work.

Most format conversion utilities on Linux are part of the netpbm package. It uses its own portable file types, designed to be easily decoded, as follows:

• pbm - Portable Bit Map, represents just a single bit depth image
• pgm - Portable Gray Map, represents up to 65536 levels of greyness
• ppm - Portable Pixel Map, represents up to 65536 r/g/b colour levels
• pam - Portable Any Map, a general-purpose grid-based storage format that the netpbm library can also handle

The programs that manipulate these formats are accessed from the commandline. They have names like 'pi1toppm' or 'pnmtopng'. The 'pnm...' ones work on any of the above formats, there isn't a separate 'pnm' format. Programs like 'pngtopnm' actually create pbm, pgm or ppm depending on the colour information in the source image. They all send output to the terminal, which you can pipe into another command or redirect into a file using standard shell operators. For example:

pi1toppm dragons.pi1 | pnmtopng > dragons.png

For many of the graphics formats, there are plugins available for the GIMP. See [1] for a complete list. GIMP also reads the netpbm formats directly.

Graphics files from the Atari ST come in roughly three flavours, described in the following sections.

Screen-size Bitmap

Use the netpbm package to convert bitmap files. It supports the following formats commonly found on the Atari:

• PI1, PC1, PI3
• NEO
• SPU, SPC
• IFF (ILBM)

It converts to a dedicated portable format (ppm), from which most other formats can be produced, such as GIF or BMP.

There is also a freeware program called XnView which is available for Linux (among other platforms) and supports a vast array of file types.

One final possibility is to use an emulator to view the file using an appropriate Atari ST application, and then use a screenshot facility (either within the emulator or from tools such as xv or the GIMP) to grab the image.

Variable-size Bitmap

There are several file types that contain bitmaps that are not complete screens:

• IMG

The GEM IMG format stores a bitmap. It can be converted using gemtopnm to create a pbm or ppm file (depending on the number of planes stored in the IMG).

• RSC

RSC files can contain icons. I don't think there's currently a way to work with these files outside of GEM.

Vector Graphics

There is a file format listed in the catalogues as "GEM: Ventura Publisher". I have no further information on this.

There may be some CAD files or outline font files that can be considered as vector formats.