Add test for gray alpha based on tRNS chunk

Add grayalpha-with-tRNS-chunk.png sourced from https://css-ig.net/articles/truepng for which the following call returns non-Zero value: png_get_valid( this->get_struct(), this->get_info(), PNG_INFO_tRNS ) Let's assume this is valid test image with tRNS chunk. Add <define>BOOST_GIL_IO_TEST_ALLOW_READING_IMAGES to Jamfile for PNG tests. NOTE: Deliberately not defined BOOST_GIL_IO_TEST_ALLOW_WRITING_IMAGES as it seems to require some extra configuration, currently it causes some tests to fail. So, Jamfile likely needs more updates and clean-up.
boostorg · Jul 16, 2019 · 8d6d783 · 8d6d783
1 parent d7884ee
commit 8d6d783
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diff --git a/test/extension/io/Jamfile b/test/extension/io/Jamfile
@@ -52,6 +52,7 @@ alias full :
       :
       :
       :
+        <define>BOOST_GIL_IO_TEST_ALLOW_READING_IMAGES
           [ ac.check-library /zlib//zlib : <library>/zlib//zlib : <build>no ]
           [ ac.check-library /libpng//libpng : <library>/libpng//libpng : <build>no ]
     ]

diff --git a/test/extension/io/images/png/grayalpha-with-tRNS-chunk.png b/test/extension/io/images/png/grayalpha-with-tRNS-chunk.png
diff --git a/test/extension/io/images/png/grayscale-with-tRNS-chunk.png b/test/extension/io/images/png/grayscale-with-tRNS-chunk.png
diff --git a/test/extension/io/png_read_test.cpp b/test/extension/io/png_read_test.cpp
@@ -125,6 +125,25 @@ BOOST_AUTO_TEST_CASE( read_pixel_per_meter )
     BOOST_CHECK_EQUAL( backend._info._pixels_per_meter, png_uint_32( 1417 ));
 }
 
+BOOST_AUTO_TEST_CASE(read_grayscale_with_trns_chunk)
+{
+    // Source of test image: bird-graylevel-a1.png at https://css-ig.net/articles/truepng
+    auto test_image = png_base_in + "grayscale-with-tRNS-chunk.png";
+    image_read_settings<png_tag> settings;
+    settings.set_read_members_true();
+
+    auto backend = read_image_info(test_image, settings);
+    BOOST_CHECK_EQUAL(backend._info._width, 200u);
+    BOOST_CHECK_EQUAL(backend._info._height, 193u);
+    BOOST_CHECK_EQUAL(backend._info._bit_depth, 8);
+    BOOST_CHECK_EQUAL(backend._info._num_channels, 1u);
+    BOOST_CHECK_EQUAL(backend._info._color_type, PNG_COLOR_TYPE_GRAY);
+
+    gray_alpha8_image_t image;
+    read_image(test_image, image, settings);
+    BOOST_CHECK_EQUAL(image.width(), 200u);
+    BOOST_CHECK_EQUAL(image.height(), 193u);
+}
 #endif // BOOST_GIL_IO_TEST_ALLOW_READING_IMAGES
 
 #ifdef BOOST_GIL_IO_USE_PNG_TEST_SUITE_IMAGES