How does one convert 16-bit RGB565 to 24-bit RGB888?

Question

I’ve got my hands on a 16-bit rgb565 image (specifically, an Android framebuffer dump), and I would like to convert it to 24-bit rgb888 for viewing on a normal monitor.

Answer 1

I used the following and got good results. Turned out my Logitek cam was 16bit RGB555 and using the following to convert to 24bit RGB888 allowed me to save as a jpeg using the smaller animals ijg: Thanks for the hint found here on stackoverflow.

// Convert a 16 bit inbuf array to a 24 bit outbuf array
BOOL JpegFile::ByteConvert(BYTE* inbuf, BYTE* outbuf, UINT width, UINT height)
{     UINT row_cnt, pix_cnt;     
      ULONG off1 = 0, off2 = 0;
      BYTE  tbi1, tbi2, R5, G5, B5, R8, G8, B8;

      if (inbuf==NULL)
          return FALSE;

      for (row_cnt = 0; row_cnt <= height; row_cnt++) 
      {     off1 = row_cnt * width * 2;
            off2 = row_cnt * width * 3;
            for(pix_cnt=0; pix_cnt < width; pix_cnt++)
            {    tbi1 = inbuf[off1 + (pix_cnt * 2)];
                 tbi2 = inbuf[off1 + (pix_cnt * 2) + 1];
                 B5 = tbi1 & 0x1F;
                 G5 = (((tbi1 & 0xE0) >> 5) | ((tbi2 & 0x03) << 3)) & 0x1F;
                 R5 = (tbi2 >> 2) & 0x1F;
                 R8 = ( R5 * 527 + 23 ) >> 6;
                 G8 = ( G5 * 527 + 23 ) >> 6;
                 B8 = ( B5 * 527 + 23 ) >> 6;
                 outbuf[off2 + (pix_cnt * 3)] = R8;
                 outbuf[off2 + (pix_cnt * 3) + 1] = G8;
                 outbuf[off2 + (pix_cnt * 3) + 2] = B8;
            }
       }
       return TRUE;
}        

Answer 2

There is an error jleedev !!!

unsigned char green = (buf & 0x07c0) >> 5;
unsigned char blue = buf & 0x003f;

the good code

unsigned char green = (buf & 0x07e0) >> 5;
unsigned char blue = buf & 0x001f;

Cheers, Andy