2020.12.11 21:43 "Re: [Tiff] SIGSEGV within TIFFGetField()", by Paavo

One thing which has frustrated me with custom tags is that (AFAICT) you can only register a custom tag on an open TIFF handle, which means you still get a bunch of warnings about unknown tags when you open the file and it reads the first IFD, before you have a chance to do the registration. Anyone know if there’s a way around that?

Sure, you register your own warning handler and ignore those warnings:

              extern "C" void MyLibtiffWarningHandler(thandle_t user_data, const char* module, const char* fmt, va_list ap) { 
                     if (strcmp(fmt, "Unknown field with tag %d (0x%x) encountered")==0) { 
                           // Unknown tags are output elsewhere, no need to issue warnings. 
                           return; 
                     } 
                     if (strcmp(fmt, "Invalid TIFF directory; tags are not sorted in ascending order") == 0) { 
                           // so? what the user must do with this message? 
                           return; 
                     } 
                     // log the warning properly 
              } 


              TIFFSetWarningHandlerExt(MyLibtiffWarningHandler); 
              // switch off default warning handler for reducing console noise. 
              TIFFSetWarningHandler(nullptr);

Cheers

Paavo