AnyImageImporter: attempt to detect AVIF files.

What a mess. Modern formats stand on a shaky pile of ancient tech.

doc/changelog.dox

@@ -1010,7 +1010,7 @@ See also:
     a file extension and MIME type corresponding to a file format produced by
     a particular plugin.
 -   Recognizing BMP and TIFF file header magic in @relativeref{Trade,AnyImageImporter}
--   Recognizing ASTC and WebP files and data in
+-   Recognizing ASTC, AVIF 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))

src/MagnumPlugins/AnyImageImporter/AnyImageImporter.cpp

@@ -73,6 +73,8 @@ void AnyImageImporter::doOpenFile(const Containers::StringView filename) {
     Containers::StringView plugin;
     if(normalizedExtension == ".astc"_s)
         plugin = "AstcImporter"_s;
+    else if(normalizedExtension == ".avif"_s)
+        plugin = "AvifImporter"_s;
     else if(normalizedExtension == ".basis"_s)
         plugin = "BasisImporter"_s;
     else if(normalizedExtension == ".bmp"_s)
@@ -206,6 +208,19 @@ void AnyImageImporter::doOpenData(Containers::Array<char>&& data, DataFlags) {
        unfortunately it being in LE means it's SCALABLE in reverse :) */
     if(dataString.hasPrefix("\x13\xAB\xA1\x5C"_s))
         plugin = "AstcImporter"_s;
+    /* Total guesswork. AVIF is an image format inside a HEIF container, which
+       itself is a ISOBMFF format, for which the spec isn't open (yay haha):
+        https://en.wikipedia.org/wiki/ISO_base_media_file_format
+       According to https://github.com/strukturag/libheif/issues/83 what
+       matters is a FourCC after the `ftyp` "box", which starts at the fourth
+       bytes, with the initial four bytes not specified anywhere. It *seems*
+       that for AVIF it's `ftypavif`, so let's check for that. In case of HEIF
+       there can be many other "brands" in a "box", whatever that is, but
+       that's suffering for another day. */
+    /** @todo https://github.com/file/file/blob/9ed4d8c65854d9d28519291f21dd92c44c4abc18/magic/Magdir/animation#L298
+        lists `avis` for image sequences, maybe detect that also? */
+    else if(dataString.size() >= 12 && dataString.slice(4, 12) == "ftypavif"_s)
+        plugin = "AvifImporter"_s;
     /* https://github.com/BinomialLLC/basis_universal/blob/7d784c728844c007d8c95d63231f7adcc0f65364/transcoder/basisu_file_headers.h#L78 */
     else if(dataString.hasPrefix("sB"_s))
         plugin = "BasisImporter"_s;

src/MagnumPlugins/AnyImageImporter/AnyImageImporter.h

@@ -61,6 +61,8 @@ Supported formats:
 -   Adaptive Scalable Texture Compression (`*.astc` or data with corresponding
     signature), loaded with @ref AstcImporter or any other plugin that provides
     it
+-   AV1 Image File Format (`*.avif` or data with corresponding signature),
+    loaded  with @ref AvifImporter or any other plugin that provides it
 -   Basis Universal (`*.basis` or data with corresponding signature), loaded
     with @ref BasisImporter or any other plugin that provides it
 -   Windows Bitmap (`*.bmp` or data with corresponding signature), loaded with

src/MagnumPlugins/AnyImageImporter/Test/AnyImageImporterTest.cpp

@@ -98,6 +98,8 @@ constexpr struct {
        variants if there are */
     {"ASTC", "8x8.astc", false, "AstcImporter"},
     {"ASTC data", "8x8.astc", true, "AstcImporter"},
+    {"AVIF", "rgb.avif", false, "AvifImporter"},
+    {"AVIF data", "rgb.avif", true, "AvifImporter"},
     {"Basis", "rgb.basis", false, "BasisImporter"},
     {"Basis data", "rgb.basis", true, "BasisImporter"},
     {"BMP", "rgb.bmp", false, "BmpImporter"},
@@ -186,7 +188,12 @@ const struct {
     {"TIFF, but no zero byte", "MM\xff\x2a"_s, "4d4dff2a"},
     {"KTX, but wrong version", "\xabKTX 30\xbb\r\n\x1a\n"_s, "ab4b5458"},
     {"RIFF (for WebP), but only 4 bytes", "RIFF"_s, "52494646"},
-    {"WebP, but only 11 bytes", "RIFF    WEB"_s, "52494646"}
+    {"WebP, but only 11 bytes", "RIFF    WEB"_s, "52494646"},
+    /* Yeah can't do \x20ftypavi because it's interpreted as 0x20f. Who thought
+       such variable-length encoding was a good idea?! Also, UGH, this message
+       in particular is rather useless, because the signature is only right
+       after that :/ */
+    {"AVIF, but not enough bytes", "\x00\x00\x00\x20" "ftypavi"_s, "00000020"},
 };
 
 constexpr struct {

src/MagnumPlugins/AnyImageImporter/Test/CMakeLists.txt

@@ -66,6 +66,7 @@ corrade_add_test(AnyImageImporterTest AnyImageImporterTest.cpp
         image.exr
         image.tiff
         pngs.ico
+        rgb.avif
         rgb.basis
         rgb.bmp
         rgb.hdr