Convert Arduino ILI9341_due library "tft.screenshotToConsole()" Serial console output to .ppm picture file

hextoppm.c

/*
   hex2ppm.c -- this is a hack.
   (Arduino ILI9341_due library ILIScreenshotViewer is Windows only)

   Just copy the hex line from Serial console to eg. "scr.hex" file.
   Then "hex2ppm src.hex > src.ppm" (followed by ppmtojpeg if needed).

   Sample "tft.screenshotToConsole();" output in serial console window:
   ==== PIXEL DATA START ====
   0000000002 ... 1D4D0D4013F000015B8
   ==== PIXEL DATA END ====
   Total Image Data Length: 5560

   encoding:
   0000000002 ... D4D0D4013F000015B8
   RRGGBBLLLL ... RRGGBBLLLL>totlen<
*/
#include <stdio.h>
#include <string.h>
#include <assert.h>

int main(int argc, char *argv[])
{
  FILE *src = (argc==1) ? stdin : fopen(argv[1], "r");
  char *ep, buf[]="0123456789";
  unsigned r,g,b,c,i,t=0;

  assert(src != NULL);

  printf("P3\n320 240\n255\n");

  while ( (1 == fread(buf, 10, 1, src)) && (isxdigit(buf[8])) )
  {
    c = strtoul(buf+6, &ep, 16);
    buf[6]='\0';
    b = strtoul(buf+4, &ep, 16);
    buf[4]='\0';
    g = strtoul(buf+2, &ep, 16);
    buf[2]='\0';
    r = strtoul(buf, &ep, 16);
    memset(buf, '\0', 10);

    for(i=0; i<c; ++i) { printf("%u %u %u ", r, g, b); }

    t += c;
  }

  assert(t == 320*240);

  t = ftell(src);
  i = strtoul(buf, &ep, 16);
  assert( (t >= i+8) && (t <= i+10));

  fclose(src);
}

Mentioned first in this Arduino forum posting:
http://forum.arduino.cc/index.php?topic=265806.msg2445130#msg2445130

hextoppm.c can be used to create animated .gif together with ppmtogif and gifsicle as well:
https://twitter.com/HermannSW/status/659466093698916352