libjpeg API: Support reading/writing ICC profiles

This commit does the following:

-- Merges the two glueware functions (read_icc_profile() and
write_icc_profile()) from iccjpeg.c, which is contained in downstream
projects such as LCMS, Ghostscript, Mozilla, etc.  These functions were
originally intended for inclusion in libjpeg, but Tom Lane left the IJG
before that could be accomplished.  Since then, programs and libraries
that needed to embed/extract ICC profiles in JPEG files had to include
their own local copy of iccjpeg.c, which is suboptimal.

   -- The new functions were prefixed with jpeg_ and split into separate
   files for the compressor and decompressor, per the existing libjpeg
   coding standards.

   -- jpeg_write_icc_profile() was made slightly more fault-tolerant.
   It will now trigger a libjpeg error if it is called before
   jpeg_start_compress() or if it is passed NULL arguments.

   -- jpeg_read_icc_profile() was made slightly more fault-tolerant.
   It will now trigger a libjpeg error if it is called before
   jpeg_read_header() or if it is passed NULL arguments.  It will also
   now trigger libjpeg warnings if the ICC profile data is corrupt.

   -- The code comments have been wordsmithed.

   -- Note that the one-line setup_read_icc_profile() function was not
   included.  Instead, libjpeg.txt now documents the need to call
   jpeg_save_markers(cinfo, JPEG_APP0 + 2, 0xFFFF) prior to calling
   jpeg_read_header(), if jpeg_read_icc_profile() is to be used.

-- Adds documentation for the new functions to libjpeg.txt.

-- Adds an -icc switch to cjpeg and jpegtran that allows those programs
to embed an ICC profile in the JPEG files they generate.

-- Adds an -icc switch to djpeg that allows that program to extract an
ICC profile from a JPEG file while decompressing.

-- Adds appropriate unit tests for all of the above.

-- Bumps the SO_AGE of the libjpeg API library to indicate the presence
of new API functions.

Note that the licensing information was obtained from:
https://github.com/mm2/Little-CMS/issues/37#issuecomment-66450180

djpeg.c

@@ -5,7 +5,7 @@
  * Copyright (C) 1991-1997, Thomas G. Lane.
  * Modified 2013 by Guido Vollbeding.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2010-2011, 2013-2016, D. R. Commander.
+ * Copyright (C) 2010-2011, 2013-2017, D. R. Commander.
  * Copyright (C) 2015, Google, Inc.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
@@ -33,6 +33,10 @@
 #include "jconfigint.h"
 #include "wrppm.h"
 
+#ifndef HAVE_STDLIB_H           /* <stdlib.h> should declare free() */
+extern void free (void *ptr);
+#endif
+
 #include <ctype.h>              /* to declare isprint() */
 
 #ifdef USE_CCOMMAND             /* command-line reader for Macintosh */
@@ -90,6 +94,7 @@ static IMAGE_FORMATS requested_fmt;
 
 
 static const char *progname;    /* program name for error messages */
+static char *icc_filename;      /* for -icc switch */
 static char *outfilename;       /* for -outfile switch */
 boolean memsrc;                 /* for -memsrc switch */
 boolean skip, crop;
@@ -158,6 +163,7 @@ usage (void)
   fprintf(stderr, "  -dither fs     Use F-S dithering (default)\n");
   fprintf(stderr, "  -dither none   Don't use dithering in quantization\n");
   fprintf(stderr, "  -dither ordered  Use ordered dither (medium speed, quality)\n");
+  fprintf(stderr, "  -icc FILE      Extract ICC profile to FILE\n");
 #ifdef QUANT_2PASS_SUPPORTED
   fprintf(stderr, "  -map FILE      Map to colors used in named image file\n");
 #endif
@@ -196,6 +202,7 @@ parse_switches (j_decompress_ptr cinfo, int argc, char **argv,
 
   /* Set up default JPEG parameters. */
   requested_fmt = DEFAULT_FMT;  /* set default output file format */
+  icc_filename = NULL;
   outfilename = NULL;
   memsrc = FALSE;
   skip = FALSE;
@@ -303,6 +310,13 @@ parse_switches (j_decompress_ptr cinfo, int argc, char **argv,
       /* Force RGB565 output. */
       cinfo->out_color_space = JCS_RGB565;
 
+    } else if (keymatch(arg, "icc", 1)) {
+      /* Set ICC filename. */
+      if (++argn >= argc)       /* advance to next argument */
+        usage();
+      icc_filename = argv[argn];
+      jpeg_save_markers(cinfo, JPEG_APP0 + 2, 0xFFFF);
+
     } else if (keymatch(arg, "map", 3)) {
       /* Quantize to a color map taken from an input file. */
       if (++argn >= argc)       /* advance to next argument */
@@ -754,6 +768,29 @@ main (int argc, char **argv)
   progress.pub.completed_passes = progress.pub.total_passes;
 #endif
 
+  if (icc_filename != NULL) {
+    FILE *icc_file;
+    JOCTET *icc_profile;
+    unsigned int icc_len;
+
+    if ((icc_file = fopen(icc_filename, WRITE_BINARY)) == NULL) {
+      fprintf(stderr, "%s: can't open %s\n", progname, icc_filename);
+      exit(EXIT_FAILURE);
+    }
+    if (jpeg_read_icc_profile(&cinfo, &icc_profile, &icc_len)) {
+      if (fwrite(icc_profile, icc_len, 1, icc_file) < 1) {
+        fprintf(stderr, "%s: can't read ICC profile from %s\n", progname,
+                icc_filename);
+        free(icc_profile);
+        fclose(icc_file);
+        exit(EXIT_FAILURE);
+      }
+      free(icc_profile);
+      fclose(icc_file);
+    } else if (cinfo.err->msg_code != JWRN_BOGUS_ICC)
+      fprintf(stderr, "%s: no ICC profile data in JPEG file\n", progname);
+  }
+
   /* Finish decompression and release memory.
    * I must do it in this order because output module has allocated memory
    * of lifespan JPOOL_IMAGE; it needs to finish before releasing memory.