Contents

Appendix A

Image file formats

This appendix describes image file formats which can be used with Imagecopy. Formats which Imagecopy uses to save images are indicated by an asterisk. Other formats can be read but not written. For general purposes, TIFF is probably the best format to use, but some ST programs have poorly implemented TIFF support (Ý A.25). Targa is a useful alternative to TIFF for true-colour and greyscale images (Ý A.24). IMG is probably the most widely supported format on Atari systems, but has problems as a colour format (Ý A.8). Other useful formats (especially for transfer to non-Atari systems) include GIF (Ý A.6), IFF (Ý A.7), PC Paintbrush (Ý A.14), and Windows Bitmap (Ý A.29). Finally, JFIF provides high compression ratios with photographic and other continuous tone images, but is not suitable for standard screen shots (Ý A.9).

A.1 Apex

This format is used by Apex Media, which is a Falcon-specific art and animation program.

Image size:	    variable.
Colour type:	  colour (8/16-bit).
Compression:	  none.
File extension:	APX.

A.2 Art Director

This ST-specific format was developed for use with the Art Director paint program. It can only represent ST low-resolution screen-sized images with 16 colours from an ST(E) palette of 512 or 4096 colours. Images are always uncompressed.

Image size:	    ST low-res (320x200).
Colour type:	  colour (4-bit).
Compression:	  none.
File extension:	ART.

A.3 Calamus Raster Graphic

This is format is used by Calamus to store monochrome image files.

Image size:	    variable.
Colour type:	  monochrome.
Compression:	  RLE.
File extension:	CRG.

A.4 *DEGAS

This ST-specific format was originally developed as a proprietary format for the DEGAS art program (later upgraded to DEGAS Elite), but has since become a common image format on ST computers. Most ST art programs read DEGAS images in addition to other formats.

In spite of its popularity, the DEGAS format has a number of serious limitations which reduce its usefulness:

1. It is a fixed-size format which cannot display images which are larger (or smaller) than an ST (or TT) screen.
2. Support for TT resolutions is an addition to the original format, and there are different varieties of TT DEGAS images. ST programs which read normal DEGAS files may be unable to read TT DEGAS files. [Following the example of ST DEGAS images (with 16-colour ST-format palettes for all resolutions), TT DEGAS images should contain a 256-colour TT palette for any resolution, and this should be stored in TT-specific format (without bit-rotation).]
3. The colour palette was originally limited to 16 colours, although this has been extended to 256 colours in TT-resolution images.
4. The colour palette is stored in ST(E) (or TT) hardware format, which uses a maximum of 12 bits for each colour (giving a palette with 4096 possible colours). The Falcon 030 palette contains 262,144 possible colours, and 24-bit palettes can distinguish over 16 million different colours.