Implement retrieving XMP metadata for tiff

Author: 1c3t3a

src/codecs/tiff.rs

@@ -20,6 +20,8 @@ use crate::error::{
 use crate::metadata::Orientation;
 use crate::{utils, ImageDecoder, ImageEncoder, ImageFormat};
 
+const TAG_XML_PACKET: Tag = Tag::Unknown(700);
+
 /// Decoder for TIFF images.
 pub struct TiffDecoder<R>
 where
@@ -264,6 +266,24 @@ impl<R: BufRead + Seek> ImageDecoder for TiffDecoder<R> {
         }
     }
 
+    fn xmp_metadata(&mut self) -> ImageResult<Option<Vec<u8>>> {
+        let Some(decoder) = &mut self.inner else {
+            return Ok(None);
+        };
+
+        let value = match decoder.get_tag(TAG_XML_PACKET) {
+            Ok(value) => value,
+            Err(tiff::TiffError::FormatError(tiff::TiffFormatError::RequiredTagNotFound(_))) => {
+                return Ok(None);
+            }
+            Err(err) => return Err(ImageError::from_tiff_decode(err)),
+        };
+        value
+            .into_u8_vec()
+            .map(Some)
+            .map_err(ImageError::from_tiff_decode)
+    }
+
     fn orientation(&mut self) -> ImageResult<Orientation> {
         if let Some(decoder) = &mut self.inner {
             Ok(decoder

tests/images/tiff/testsuite/l1_xmp.tiff

@@ -6,6 +6,8 @@ use image::ImageDecoder;
 
 #[cfg(feature = "png")]
 use image::codecs::png::PngDecoder;
+#[cfg(feature = "tiff")]
+use image::codecs::tiff::TiffDecoder;
 #[cfg(feature = "webp")]
 use image::codecs::webp::WebPDecoder;
 
@@ -18,6 +20,9 @@ const EXPECTED_PNG_METADATA: &str = "<?xpacket begin='\u{feff}' id='W5M0MpCehiHz
 const XMP_WEBP_PATH: &str = "tests/images/webp/lossless_images/simple_xmp.webp";
 const EXPECTED_WEBP_METADATA: &str = "<?xpacket begin='\u{feff}' id='W5M0MpCehiHzreSzNTczkc9d'?>\n<x:xmpmeta xmlns:x='adobe:ns:meta/' x:xmptk='Image::ExifTool 13.25'>\n<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>\n\n <rdf:Description rdf:about=''\n  xmlns:dc='http://purl.org/dc/elements/1.1/'>\n  <dc:subject>\n   <rdf:Bag>\n    <rdf:li>sunset, mountains, nature</rdf:li>\n   </rdf:Bag>\n  </dc:subject>\n </rdf:Description>\n</rdf:RDF>\n</x:xmpmeta>\n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n<?xpacket end='w'?>";
 
+const XMP_TIFF_PATH: &str = "tests/images/tiff/testsuite/l1_xmp.tiff";
+const EXPECTED_METADATA_TIFF: &str = "<?xpacket begin='\u{feff}' id='W5M0MpCehiHzreSzNTczkc9d'?>\n<x:xmpmeta xmlns:x='adobe:ns:meta/' x:xmptk='Image::ExifTool 13.25'>\n<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>\n\n <rdf:Description rdf:about=''\n  xmlns:dc='http://purl.org/dc/elements/1.1/'>\n  <dc:subject>\n   <rdf:Bag>\n    <rdf:li>sunset, mountains, nature</rdf:li>\n   </rdf:Bag>\n  </dc:subject>\n </rdf:Description>\n</rdf:RDF>\n</x:xmpmeta>\n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n                                                                                                    \n<?xpacket end='w'?>";
+
 #[test]
 #[cfg(feature = "png")]
 fn test_read_xmp_png() -> Result<(), image::ImageError> {
@@ -46,3 +51,17 @@ fn test_read_xmp_webp() -> Result<(), image::ImageError> {
 
     Ok(())
 }
+
+#[test]
+#[cfg(feature = "tiff")]
+fn test_read_xmp_tiff() -> Result<(), image::ImageError> {
+    let img_path = PathBuf::from_str(XMP_TIFF_PATH).unwrap();
+
+    let data = fs::read(img_path)?;
+    let mut tiff_decoder = TiffDecoder::new(std::io::Cursor::new(data))?;
+    let metadata = tiff_decoder.xmp_metadata()?;
+    assert!(metadata.is_some());
+    assert_eq!(EXPECTED_METADATA_TIFF.as_bytes(), metadata.unwrap());
+
+    Ok(())
+}