8 bit colour palette: more information - Raspberry Pi Forums

hi,

found thread http://www.raspberrypi.org/phpbb3/viewt ... 72&t=11682 in bare metal forum - went on reply before realising more appropriate forum...

hereby try branch discussion here:

-rst- wrote:

dom wrote:yes, , 16-bit format 5 bits red, 6 bits green, 5 bits blue.
8bpp default "web safe" palette, can set. see:
https://github.com/raspberrypi/linux/bl ... m2708_fb.c

hmm, seems driver code, not directly accessible user-mode applications? or have missed way access this...

framebuffer ioctl method not seem work on rpi - code:

code: select all

#include <linux/fb.h> ...   fbfd = open("/dev/fb0", o_rdwr); ...   if (ioctl(fbfd, fbioget_vscreeninfo, &vinfo)) {     printf("error reading variable information.\n");     close(fbfd);     return(3);   }   printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel );    // palette information   unsigned short r[256];   unsigned short g[256];   unsigned short b[256];   unsigned short a[256];   memset(r, 0xff, 256 * sizeof(unsigned short));   memset(g, 0xff, 256 * sizeof(unsigned short));   memset(b, 0xff, 256 * sizeof(unsigned short));   memset(a, 0xff, 256 * sizeof(unsigned short));   struct fb_cmap cmap;   cmap.start = 0;   cmap.len = 256;   cmap.red = r;   cmap.green = g;   cmap.blue = b;   cmap.transp = a;   if (ioctl(fbfd, fbiogetcmap, &cmap)) {     printf("error reading palette.\n");     close(fbfd);     return(4);   } ... 

succeeds print out resolution , bit depth, fails read palette (regardless of mode set using 'fbset -depth x').

know other ways access driver (to set palette)?

thanks,

jp

question remains: way access driver? , possibly bug in driver (google 'fbiogetcmap fail' finds bug reports other drivers...)?

thanks,

jp

uh, ok - time carefulness seems have 'bitten me in leg'... hoping read default cmap , save restoring, did not try fbioputcmap ...which seems work!!! used 'fbset -depth 8' before running test app.

easy mangle display prompt etc. lost, 'blind typing' command 'fbset -depth 16' luckily restores default palette.

question is: if fb palette change applies 8 bit gpu/vc resources too... well, time sleep - i'll try out tomorrow!

raspberrypi