This command takes the current screen contents and compresses them, saving the picture in its compressed form in the stated file - the full filename (eg. ram1_test_scr) has to be used.
This compressed form does not represent that great a saving over the original 32768 bytes required to hold the details of the screen before compression - the amount of space required for a compressed screen depends upon the amount of adjacent pixels on the screen which have the same colour.
Whilst the screen is compressed, a pattern is drawn over the screen, which although annoying, is harmless.
COMPRESS temporarily needs 64K of working space and will report an error if this is not available. Unfortunately the file stays open if this happens and cannot be accessed until is is closed with CLOSE% or a desktop program such as QPAC 2 (channels menu).
COMPRESS does not work in supervisor mode, ie. it multitasks, thus if you were doing something else whilst the screen was being compressed, the saved picture may look pretty strange when expanded.
COMPRESS assumes that the screen starts at $20000 and cannot therefore be used with Minerva’s second screen or some emulator display modes.
COMPRESS assumes a screen resolution of 512x256 and cannot work on higher resolution screens.
See also SCR_STORE.