Oberon-pictures

Grapes.Pict

Escher.Pict

Supported interface

PROCEDURE Store*(P: Picture; VAR R: Files.Rider; VAR len: INTEGER);
PROCEDURE New*(w, h, dpt: INTEGER) : Picture;
PROCEDURE Load*(VAR R: Files.Rider; VAR len: INTEGER) : Picture;
PROCEDURE Open*(name: ARRAY OF CHAR) : Picture;
PROCEDURE Show*;

Notes

Pictures module currently has only a minimal interface, to show, load, and store rle encoded pictures. There are two B&W pictures provided 'Grapes.Pict', 'Escher.Pict', these date back to days of Xerox Alto, and Ceres workstations. To display use the commands:

Pictures.Show Grapes.Pict 30 30 ~
Pictures.Show Escher.Pict 30 30 ~

It decodes rle picture into bitmap, and displays at given coordinates.

RLETest module provide some functionality for testing of the rle encoding. To test RLE use the commands:

RLETest.Run
RLETest.Pict

Former will first set picture's bitmap to a run of bytes, then it reports the same run rle encoded, the latter will decode 'Grapes.Pict' and encode it back to 'Test.Pict' producing identical file.

ETH Picture format definition

LSB = <00> | <01> | ... | <FE> | <FF>.
MSB = <00> | <01> | ... | <FE> | <FF>.

PictFile = ID Width Height ColorTable { Run } .
ID = <03> <F0>.
Width = LSB MSB.
Height = LSB MSB.
ColorTable = Depth { R G B }
Depth = LSB MSB
R = LSB.
G = LSB.
B = LSB.
Run = Compressed | Uncompressed.
Compressed = Negative LSB.
Uncompressed = Positive { LSB }.
Negative = <80> | <81> | ... | <FF>.
Positive = <00> | <01> | ... | <7F>.

• Width, Height and Depth are integer values (MSB * 256 + LSB).
• ColorTable has 2^Depth RGB entries.
• Negative: Copy (256-Negative) times the LSB of RLE to the screen.
• Positive: Transfer (Positive+1) bytes in the file 1:1 to the screen.