Check for errors when loading or saving an image with Imlib2.

This relies on the definition of enum _imlib_load_error in Imlib2.h
and might break on different versions of Imlib2, but should be better
than the total lack of error reporting before.

Developed with Imlib2 version 1.4.5 from Debian/Sid:

$ dpkg -l libimlib2-dev
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-=================================
ii  libimlib2-dev  1.4.5-1      i386         Imlib2 development files

imgproc.c

@@ -1017,6 +1017,7 @@ void save_image(const char *image_type, Imlib_Image *image, const char *fmt,
 {
   const char *tmp;
   Imlib_Image *current_image;
+  Imlib_Load_Error save_error=0;
   const char *const stdout_file = "/proc/self/fd/1";
 
   current_image = imlib_context_get_image();
@@ -1045,7 +1046,11 @@ void save_image(const char *image_type, Imlib_Image *image, const char *fmt,
   /* write image to disk */
   if(flags & VERBOSE)
     fprintf(stderr, "writing %s image to file %s\n", image_type, filename);
-  imlib_save_image(filename);
+  imlib_save_image_with_error_return(filename, &save_error);
+  if(save_error && save_error != IMLIB_LOAD_ERROR_NONE) {
+    fprintf(stderr, "error saving image file %s\n", filename);
+    report_imlib_error(save_error);
+  }
   imlib_context_set_image(current_image);
 }
 
@@ -1075,3 +1080,59 @@ luminance_t parse_lum(char *keyword)
     return DEFAULT_LUM_FORMULA;
   }
 }
+
+/* report Imlib2 load/save error to stderr */
+void report_imlib_error(Imlib_Load_Error error)
+{
+  fputs("  Imlib2 error code: ",stderr);
+  switch (error) {
+    case IMLIB_LOAD_ERROR_NONE:
+      fputs("IMLIB_LOAD_ERROR_NONE\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_FILE_DOES_NOT_EXIST:
+      fputs("IMLIB_LOAD_ERROR_FILE_DOES_NOT_EXIST\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_FILE_IS_DIRECTORY:
+      fputs("IMLIB_LOAD_ERROR_FILE_IS_DIRECTORY\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_PERMISSION_DENIED_TO_READ:
+      fputs("IMLIB_LOAD_ERROR_PERMISSION_DENIED_TO_READ\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_NO_LOADER_FOR_FILE_FORMAT:
+      fputs("IMLIB_LOAD_ERROR_NO_LOADER_FOR_FILE_FORMAT\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_PATH_TOO_LONG:
+      fputs("IMLIB_LOAD_ERROR_PATH_TOO_LONG\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_PATH_COMPONENT_NON_EXISTANT:
+      fputs("IMLIB_LOAD_ERROR_PATH_COMPONENT_NON_EXISTANT\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_PATH_COMPONENT_NOT_DIRECTORY:
+      fputs("IMLIB_LOAD_ERROR_PATH_COMPONENT_NOT_DIRECTORY\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_PATH_POINTS_OUTSIDE_ADDRESS_SPACE:
+      fputs("IMLIB_LOAD_ERROR_PATH_POINTS_OUTSIDE_ADDRESS_SPACE\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_TOO_MANY_SYMBOLIC_LINKS:
+      fputs("IMLIB_LOAD_ERROR_TOO_MANY_SYMBOLIC_LINKS\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_OUT_OF_MEMORY:
+      fputs("IMLIB_LOAD_ERROR_OUT_OF_MEMORY\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_OUT_OF_FILE_DESCRIPTORS:
+      fputs("IMLIB_LOAD_ERROR_OUT_OF_FILE_DESCRIPTORS\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_PERMISSION_DENIED_TO_WRITE:
+      fputs("IMLIB_LOAD_ERROR_PERMISSION_DENIED_TO_WRITE\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_OUT_OF_DISK_SPACE:
+      fputs("IMLIB_LOAD_ERROR_OUT_OF_DISK_SPACE\n", stderr);
+      break;
+    case IMLIB_LOAD_ERROR_UNKNOWN:
+      fputs("IMLIB_LOAD_ERROR_UNKNOWN\n", stderr);
+      break;
+    default:
+      fprintf(stderr, "unknown error code %d, please report\n", error);
+      break;
+  }
+}

imgproc.h

@@ -171,4 +171,7 @@ int clip(int value, int min, int max);
 void save_image(const char *image_type, Imlib_Image *image, const char *fmt,
                 const char *filename, int flags);
 
+/* report Imlib2 load/save error to stderr */
+void report_imlib_error(Imlib_Load_Error error);
+
 #endif /* SSOCR2_IMGPROC_H */

ssocr.c

@@ -113,6 +113,7 @@ int main(int argc, char **argv)
   Imlib_Image image=NULL; /* an image handle */
   Imlib_Image new_image=NULL; /* a temporary image handle */
   Imlib_Image debug_image=NULL; /* DEBUG */
+  Imlib_Load_Error load_error=0; /* save Imlib2 error code on image I/O*/
   char *imgfile=NULL; /* filename of image file */
   int use_tmpfile=0; /* flag to know if temporary image file is used */
 
@@ -379,7 +380,7 @@ int main(int argc, char **argv)
   if(flags & VERBOSE) {
     fprintf(stderr, "loading image %s\n", imgfile);
   }
-  image = imlib_load_image_immediately_without_cache(imgfile);
+  image = imlib_load_image_with_error_return(imgfile, &load_error);
   if(use_tmpfile) {
     if(flags & VERBOSE)
       fprintf(stderr, "removing temporary image file %s\n", imgfile);
@@ -389,6 +390,7 @@ int main(int argc, char **argv)
   }
   if(!image) {
     fprintf(stderr, "could not load image %s\n", imgfile);
+    report_imlib_error(load_error);
     exit(99);
   }