AnyImageImporter: recognize also the other Radiance HDR file signature.

doc/changelog.dox

@@ -944,6 +944,8 @@ See also:
 -   Recognizing BMP and TIFF file header magic in @relativeref{Trade,AnyImageImporter}
 -   Recognizing ASTC and WebP files and data in
     @relativeref{Trade,AnyImageImporter}
+-   Recognizing also a second variant of Radiance HDR file headers in
+    @relativeref{Trade,AnyImageImporter} (see [mosra/magnum#652](https://github.com/mosra/magnum/issues/652))
 -   Recognizing KTX2 files and data in @relativeref{Trade,AnyImageImporter} and
     @relativeref{Trade,AnyImageConverter} (see also
     [mosra/magnum#529](https://github.com/mosra/magnum/pull/529))

src/MagnumPlugins/AnyImageImporter/AnyImageImporter.cpp

@@ -215,8 +215,16 @@ void AnyImageImporter::doOpenData(Containers::Array<char>&& data, DataFlags) {
     /* http://www.openexr.com/openexrfilelayout.pdf */
     else if(dataString.hasPrefix("\x76\x2f\x31\x01"_s))
         plugin = "OpenExrImporter"_s;
-    /* https://en.wikipedia.org/wiki/Radiance_(software)#HDR_image_format */
-    else if(dataString.hasPrefix("#?RADIANCE"_s))
+    /* https://en.wikipedia.org/wiki/Radiance_(software)#HDR_image_format and
+       https://en.wikipedia.org/wiki/RGBE_image_format which lists also the \n
+       at the end. There's also a RGBE signature that isn't mentioned on
+       Wikipedia, at https://paulbourke.net/dataformats/pic/ or used by the
+       file utility https://github.com/file/file/blob/0fa2c8c3e64c372d038d46969bafaaa09a13a87b/magic/Magdir/images#L2755-L2759
+       but is used by https://www.graphics.cornell.edu/~bjw/rgbe/rgbe.c which
+       is subsequently derived from in e.g. https://github.com/kopaka1822/ImageViewer/blob/5ec358cf5c3f818c0cc4c363f5ec0c61aa99d372/dependencies/hdr/rgbe.h#L210
+       and stb_image recognizes that as well. */
+    else if(dataString.hasPrefix("#?RADIANCE\n"_s) ||
+            dataString.hasPrefix("#?RGBE\n"_s))
         plugin = "HdrImporter"_s;
     /* https://en.wikipedia.org/wiki/JPEG#Syntax_and_structure */
     else if(dataString.hasPrefix("\xff\xd8\xff"_s))

src/MagnumPlugins/AnyImageImporter/Test/AnyImageImporterTest.cpp

@@ -102,6 +102,7 @@ constexpr struct {
     {"JPEG2000", "image.jp2", false, "Jpeg2000Importer"},
     {"HDR", "rgb.hdr", false, "HdrImporter"},
     {"HDR data", "rgb.hdr", true, "HdrImporter"},
+    {"HDR data, different signature", "rgb.2.hdr", true, "HdrImporter"},
     {"ICO", "pngs.ico", false, "IcoImporter"},
     {"DDS", "rgba_dxt1.dds", false, "DdsImporter"},
     {"DDS data", "rgba_dxt1.dds", true, "DdsImporter"},
@@ -159,6 +160,7 @@ const struct {
     {"just one byte", "\x33"_s, "33"},
     {"just one zero byte", "\x00"_s, "00"},
     {"DDS, but no space", "DDS!"_s, "44445321"},
+    {"HDR, but without the trailing newline", "#?RADIANCE."_s, "233f5241"},
     {"TIFF, but too short", "II\x2a"_s, "49492a"},
     {"TIFF, but no zero byte", "MM\xff\x2a"_s, "4d4dff2a"},
     {"KTX, but wrong version", "\xabKTX 30\xbb\r\n\x1a\n"_s, "ab4b5458"},

src/MagnumPlugins/AnyImageImporter/Test/CMakeLists.txt

@@ -67,6 +67,8 @@ corrade_add_test(AnyImageImporterTest AnyImageImporterTest.cpp
         rgb.basis
         rgb.bmp
         rgb.hdr
+        # Created using https://github.com/kopaka1822/ImageViewer/
+        rgb.2.hdr
         rgb.png
         rgb.tga
         rgba_dxt1.dds