Catch and throw PNG exceptions - fixes #1213

The png library uses setjmp/longjmp to throw exceptions when reading. If this
is not set up, the png library calls abort(). This change handles the errors
and throws a C++ exception instead.

This issue was found by testing images from pngsuite at
http://www.schaik.com/pngsuite/. These images are included and a unit test was
added to test both images that should be successful and images that should
throw an exception.

src/png_reader.cpp

@@ -119,6 +119,13 @@ void png_reader::init()
         throw image_reader_exception("failed to create info_ptr");
     }
 
+    if (setjmp(png_jmpbuf(png_ptr)))
+    {
+        png_destroy_read_struct(&png_ptr,0,0);
+        fclose(fp);
+        throw image_reader_exception("failed to read");
+    }
+
     png_set_read_fn(png_ptr, (png_voidp)fp, png_read_data);
 
     png_set_sig_bytes(png_ptr,8);
@@ -168,6 +175,13 @@ void png_reader::read(unsigned x0, unsigned y0,image_data_32& image)
         throw image_reader_exception("failed to create info_ptr");
     }
 
+    if (setjmp(png_jmpbuf(png_ptr)))
+    {
+        png_destroy_read_struct(&png_ptr,0,0);
+        fclose(fp);
+        throw image_reader_exception("failed to read");
+    }
+
     png_set_read_fn(png_ptr, (png_voidp)fp, png_read_data);
     png_read_info(png_ptr, info_ptr);
 

tests/data/pngsuite/PngSuite.LICENSE

@@ -0,0 +1,9 @@
+PngSuite
+--------
+
+Permission to use, copy, modify and distribute these images for any
+purpose and without fee is hereby granted.
+
+
+(c) Willem van Schaik, 1996, 2011
+

tests/data/pngsuite/PngSuite.README

@@ -0,0 +1,25 @@
+        PNGSUITE
+----------------
+
+        testset for PNG-(de)coders
+        created by Willem van Schaik
+------------------------------------
+
+This is a collection of graphics images created to test the png applications
+like viewers, converters and editors. All (as far as that is possible)
+formats supported by the PNG standard are represented.
+
+The suite consists of the following files:
+
+-	PngSuite.README		- this file
+-	PngSuite.LICENSE	- the PngSuite is freeware
+-	PngSuite.png		- image with PngSuite logo
+-	PngSuite.tgz		- archive of all PNG testfiles
+-	PngSuite.zip		- same in .zip format for PCs
+
+
+--------
+    (c) Willem van Schaik
+	willem@schaik.com
+        Calgary, April 2011
+