Unoffical empeg BBS

Quick Links: Empeg FAQ | RioCar.Org | Hijack | BigDisk Builder | jEmplode | emphatic
Repairs: Repairs

Topic Options
#20154 - 12/10/2000 05:47 grabbing the empeg screen
mschrag
pooh-bah

Registered: 09/09/2000
Posts: 2303
Loc: Richmond, VA
Why is it that grabscreen returns a 2048 byte array (and appears to be 4 bits per pixel) if the empeg is only 2 bits per pixel? Did I fall asleep in class and miss something :) ?

Mike


Top
#20155 - 12/10/2000 06:02 Re: grabbing the empeg screen [Re: mschrag]
fvgestel
old hand

Registered: 12/08/2000
Posts: 702
Loc: Netherlands
You're right, it doesn't make sense. per byte there are only 4 bits used.

00 00 00 00
^^ ^^
rp lp


lp=left pixel
rp=right pixel

As I recall, it is possible to use 4 bits/pixel, but this would make the screen blurry/difficult to read. I wrote a java applet which also receives the screenbuffer 20 times per second; I will update it this week to only send/receive 1024 bytes as this would significantly reduce network-bandwith

Frank van Gestel
_________________________
Frank van Gestel

Top
#20156 - 12/10/2000 07:13 Re: grabbing the empeg screen [Re: mschrag]
altman
carpal tunnel

Registered: 19/05/1999
Posts: 3457
Loc: Palo Alto, CA
The hardware is 4bpp, however there are only 4 useful colours in that space. The display is run through a palette by the hardware too. Actually, the hardware screen buffer is a very frightening layout (read the comment at the start of arch/arm/special/empeg_display.c).

We may well use another grey in future, as there's another useful one we've found...

Hugo



Top
#20157 - 12/10/2000 09:41 Re: grabbing the empeg screen [Re: mschrag]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
Another thing...

When looking at binary logo files with an editor, this format makes it really easy to see the pixel layout. Each nibble is either a 0, 1, 2, or 3, each number representing the corresponding color. It also makes writing bitmashing and pixel-pushing algorithms very easy (as I discovered last night while working on my logo editor).

___________
Tony Fabris
_________________________
Tony Fabris

Top
#20158 - 12/10/2000 09:54 Re: grabbing the empeg screen [Re: tfabris]
mschrag
pooh-bah

Registered: 09/09/2000
Posts: 2303
Loc: Richmond, VA
I definitely agree it makes life easier ... My first version of the Java renderer did 2 bit bitmanip, and it produced pretty funny looking output.


Top