Recognize certain sRGB profiles by their crc32.

diff --git a/coders/png.c b/coders/png.c
index d7d2441515e70a7bbc756ffb16b9ad7c9cb7b55e..905e61ee97c6706d219fbf4c59ab9ccee53a6527 100644 (file)
--- a/coders/png.c
+++ b/coders/png.c
@@ -7628,59 +7628,54 @@ static MagickBooleanType WriteOnePNGImage(MngInfo *mng_info,
             if ((LocaleCompare(name,"ICC") == 0) ||
                (LocaleCompare(name,"ICM") == 0))
               {
-                 unsigned char
-                   *data;
+                 int
+                   icheck;
 
+                 /* 0: not a known sRGB profile
+                  * 1: HP-Microsoft sRGB v2
+                  * 2: ICC sRGB v4 perceptual
+                  * 3: ICC sRGB v2 perceptual no black-compensation
+                  */
                  png_uint_32
-                   length;
+                   check_crc[4] = {0, 0xf29e526dUL, 0xbbef7812UL, 0x427ebb21UL},
+                   check_len[4] = {0, 3144, 60960, 3052};
 
-                 length=(png_uint_32) GetStringInfoLength(profile);
+                 png_uint_32
+                   length,
+                   profile_crc;
 
-                 if (length == 3144)
-                 {
-                   (void) LogMagickEvent(CoderEvent,GetMagickModule(),
-                       "    got a 3144-byte ICC profile (potentially sRGB)");
+                 unsigned char
+                   *data;
 
-                   data=GetStringInfoDatum(profile);
+                 length=(png_uint_32) GetStringInfoLength(profile);
 
-                   if (data[52]=='s' && data[53]=='R' &&
-                       data[54]=='G' && data[55]=='B')
-                   {
-                      (void) LogMagickEvent(CoderEvent,GetMagickModule(),
-                          "    It is the HP-Microsoft sRGB)");
-                      if (image->rendering_intent==UndefinedIntent)
-                        image->rendering_intent=PerceptualIntent;
-                   }
-                   else
-                      (void) LogMagickEvent(CoderEvent,GetMagickModule(),
-                          "    It is not sRGB (%c%c%c%c)",data[52],
-                          data[53],data[54],data[55]);
-                   
-                 }
-                 else if (length == 3052)
+                 for (icheck=3; icheck > 0; icheck--)
                  {
-                   (void) LogMagickEvent(CoderEvent,GetMagickModule(),
-                       "    got a 3052-byte ICC profile (potentially sRGB)");
+                   if (length == check_len[icheck])
+                   {
+                     (void) LogMagickEvent(CoderEvent,GetMagickModule(),
+                         "    Got a %lu-byte ICC profile (potentially sRGB)",
+                         (unsigned long) length);
 
-                   data=GetStringInfoDatum(profile);
+                     data=GetStringInfoDatum(profile);
+                     profile_crc=crc32(0,data,length);
 
-                   if (data[336]=='s' && data[337]=='R' &&
-                       data[338]=='G' && data[339]=='B')
-                   {
-                      (void) LogMagickEvent(CoderEvent,GetMagickModule(),
-                          "    It is the ICC no-black sRGB)");
-                      if (image->rendering_intent==UndefinedIntent)
-                        image->rendering_intent=PerceptualIntent;
+                     (void) LogMagickEvent(CoderEvent,GetMagickModule(),
+                         "      with crc=%8x",profile_crc);
+
+                     if (profile_crc == check_crc[icheck])
+                     {
+                        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
+                            "      It is sRGB.");
+                        if (image->rendering_intent==UndefinedIntent)
+                          image->rendering_intent=PerceptualIntent;
+                        break;
+                     }
                    }
-                   else
-                      (void) LogMagickEvent(CoderEvent,GetMagickModule(),
-                          "    It is not sRGB (%c%c%c%c)",data[52],
-                          data[53],data[54],data[55]);
-                   
                  }
-                 else
+                 if (icheck == 0)
                     (void) LogMagickEvent(CoderEvent,GetMagickModule(),
-                        "    got a %lu-byte ICC profile",
+                        "    Got a %lu-byte ICC profile",
                         (unsigned long) length);
               }
           }