Add support for decoding to 565 to libjpeg_turbo

djpeg.c

 /*
  * djpeg.c
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2010-2011, 2013-2015, D. R. Commander.
  * Copyright (C) 2015, Google, Inc.
  * For conditions of distribution and use, see the accompanying README file.
  *
@@ skipping 92 matching lines @@
   fprintf(stderr, "inputfile outputfile\n");
 #else
   fprintf(stderr, "[inputfile]\n");
 #endif
 
   fprintf(stderr, "Switches (names may be abbreviated):\n");
   fprintf(stderr, "  -colors N      Reduce image to no more than N colors\n");
   fprintf(stderr, "  -fast          Fast, low-quality processing\n");
   fprintf(stderr, "  -grayscale     Force grayscale output\n");
   fprintf(stderr, "  -rgb           Force RGB output\n");
+  fprintf(stderr, "  -rgb565        Force RGB565 output\n");
 #ifdef IDCT_SCALING_SUPPORTED
   fprintf(stderr, "  -scale M/N     Scale output image by fraction M/N, eg, 1/8\n");
 #endif
 #ifdef BMP_SUPPORTED
   fprintf(stderr, "  -bmp           Select BMP output format (Windows style)%s\n",
           (DEFAULT_FMT == FMT_BMP ? " (default)" : ""));
 #endif
 #ifdef GIF_SUPPORTED
   fprintf(stderr, "  -gif           Select GIF output format%s\n",
           (DEFAULT_FMT == FMT_GIF ? " (default)" : ""));
@@ skipping 158 matching lines @@
       requested_fmt = FMT_GIF;
 
     } else if (keymatch(arg, "grayscale", 2) || keymatch(arg, "greyscale",2)) {
       /* Force monochrome output. */
       cinfo->out_color_space = JCS_GRAYSCALE;
 
     } else if (keymatch(arg, "rgb", 2)) {
       /* Force RGB output. */
       cinfo->out_color_space = JCS_RGB;
 
+    } else if (keymatch(arg, "rgb565", 2)) {
+      /* Force RGB565 output. */
+      cinfo->out_color_space = JCS_RGB565;
+
     } else if (keymatch(arg, "map", 3)) {
       /* Quantize to a color map taken from an input file. */
       if (++argn >= argc)       /* advance to next argument */
         usage();
       if (for_real) {           /* too expensive to do twice! */
 #ifdef QUANT_2PASS_SUPPORTED    /* otherwise can't quantize to supplied map */
         FILE * mapfile;
 
         if ((mapfile = fopen(argv[argn], READ_BINARY)) == NULL) {
           fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);
@@ skipping 433 matching lines @@
   end_progress_monitor((j_common_ptr) &cinfo);
 #endif
 
   if (memsrc && inbuffer != NULL)
     free(inbuffer);
 
   /* All done. */
   exit(jerr.num_warnings ? EXIT_WARNING : EXIT_SUCCESS);
   return 0;                     /* suppress no-return-value warnings */
 }