cwebp: add -metadata option

currently has no effect except to disable metadata extraction from the
input when the value is 'none'.

Change-Id: Ic50d4c9d634cc1f6b72ae4e130e99736c85a6477

README

@@ -171,6 +171,10 @@ options:
   -hint <string> ......... Specify image characteristics hint.
                            One of: photo, picture or graph
 
+  -metadata <string> ..... comma separated list of metadata to
+                           copy from the input to the output if present.
+                           Valid values: all, none (default), exif, iccp, xmp
+
   -short ................. condense printed message
   -quiet ................. don't print anything.
   -version ............... print version number and exit.

examples/cwebp.c

@@ -545,6 +545,16 @@ static int DumpPicture(const WebPPicture* const picture, const char* PGM_name) {
   return 1;
 }
 
+// -----------------------------------------------------------------------------
+// Metadata writing.
+
+enum {
+  METADATA_EXIF = (1 << 0),
+  METADATA_ICCP = (1 << 1),
+  METADATA_XMP  = (1 << 2),
+  METADATA_ALL  = METADATA_EXIF | METADATA_ICCP | METADATA_XMP
+};
+
 //------------------------------------------------------------------------------
 
 static int ProgressReport(int percent, const WebPPicture* const picture) {
@@ -617,6 +627,13 @@ static void HelpLong(void) {
   printf("  -hint <string> ......... Specify image characteristics hint.\n");
   printf("                           One of: photo, picture or graph\n");
 
+  printf("\n");
+  printf("  -metadata <string> ..... comma separated list of metadata to\n");
+  printf("                           ");
+  printf("copy from the input to the output if present.\n");
+  printf("                           "
+         "Valid values: all, none (default), exif, iccp, xmp\n");
+
   printf("\n");
   printf("  -short ................. condense printed message\n");
   printf("  -quiet ................. don't print anything.\n");
@@ -669,6 +686,7 @@ int main(int argc, const char *argv[]) {
   int crop = 0, crop_x = 0, crop_y = 0, crop_w = 0, crop_h = 0;
   int resize_w = 0, resize_h = 0;
   int show_progress = 0;
+  int keep_metadata = 0;
   WebPPicture picture;
   int print_distortion = -1;        // -1=off, 0=PSNR, 1=SSIM, 2=LSIM
   WebPPicture original_picture;    // when PSNR or SSIM is requested
@@ -832,6 +850,50 @@ int main(int argc, const char *argv[]) {
         fprintf(stderr, "Error! Could initialize configuration with preset.\n");
         goto Error;
       }
+    } else if (!strcmp(argv[c], "-metadata") && c < argc - 1) {
+      static const struct {
+        const char* option;
+        int flag;
+      } kTokens[] = {
+        { "all",  METADATA_ALL },
+        { "none", 0 },
+        { "exif", METADATA_EXIF },
+        { "iccp", METADATA_ICCP },
+        { "xmp",  METADATA_XMP },
+      };
+      const size_t kNumTokens = sizeof(kTokens) / sizeof(kTokens[0]);
+      const char* start = argv[++c];
+      const char* const end = start + strlen(start);
+
+      while (start < end) {
+        size_t i;
+        const char* token = strchr(start, ',');
+        if (token == NULL) token = end;
+
+        for (i = 0; i < kNumTokens; ++i) {
+          if ((size_t)(token - start) == strlen(kTokens[i].option) &&
+              !strncmp(start, kTokens[i].option, strlen(kTokens[i].option))) {
+            if (kTokens[i].flag != 0) {
+              keep_metadata |= kTokens[i].flag;
+            } else {
+              keep_metadata = 0;
+            }
+            break;
+          }
+        }
+        if (i == kNumTokens) {
+          fprintf(stderr, "Error! Unknown metadata type '%.*s'\n",
+                  (int)(token - start), start);
+          HelpLong();
+          return -1;
+        }
+        start = token + 1;
+      }
+      if (keep_metadata != 0) {
+        // TODO(jzern): remove when -metadata is supported on all platforms.
+        fprintf(stderr, "Warning: -metadata is currently unsupported on this"
+                        " platform. Ignoring this option!\n");
+      }
     } else if (!strcmp(argv[c], "-v")) {
       verbose = 1;
     } else if (argv[c][0] == '-') {
@@ -870,7 +932,8 @@ int main(int argc, const char *argv[]) {
   if (verbose) {
     StopwatchReadAndReset(&stop_watch);
   }
-  if (!ReadPicture(in_file, &picture, keep_alpha, &metadata)) {
+  if (!ReadPicture(in_file, &picture, keep_alpha,
+                   (keep_metadata == 0) ? NULL : &metadata)) {
     fprintf(stderr, "Error! Cannot read input picture file '%s'\n", in_file);
     goto Error;
   }

man/cwebp.1

@@ -1,5 +1,5 @@
 .\"                                      Hey, EMACS: -*- nroff -*-
-.TH CWEBP 1 "November 15, 2012"
+.TH CWEBP 1 "January 11, 2013"
 .SH NAME
 cwebp \- compress an image file to a WebP file
 .SH SYNOPSIS
@@ -172,6 +172,14 @@ Encode the image without any loss.
 Specify the hint about input image type. Possible values are:
 \fBphoto\fP, \fBpicture\fP or \fBgraph\fP.
 .TP
+.B \-metadata string
+A comma separated list of metadata to copy from the input to the output if
+present.
+Valid values: \fBall\fP, \fBnone\fP, \fBexif\fP, \fBiccp\fP, \fBxmp\fP.
+The default is \fBnone\fP.
+
+Note: each input format may not support all combinations.
+.TP
 .B \-noasm
 Disable all assembly optimizations.
 .TP