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

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

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

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).

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Tony Fabris

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.