Changelog entry for tile treatment

CHANGES.md

@@ -11,6 +11,12 @@ Changes:
   directory state if they fail. This includes the failure to interpret an IFD
   as a supported image in the case of `*_image` variants.
 
+Compatibility:
+- Changed how tiled TIFF files are detected. The presence of a TileWidth OR
+  TileHeight/TileLength tag now marks an image as tiled. Data is no retrieved
+  from either StripOffsets or TileOffsets with the latter taking precedence.
+  This is closer to the behavior of libtiff.
+
 # Version 0.11.3
 
 Additions:

src/decoder/image.rs

@@ -330,113 +330,114 @@ impl Image {
             PlanarConfiguration::Planar => samples,
         };
 
+        // Note: Not strictly according to specification. The specification says that tiled images
+        // must have their data encoded in `TileByteCounts` and `TileOffsets`. But `libtiff`
+        // processes tags one-by-one and with *either* of these it will set the flag for the image
+        // being tiled. Also it will just use whatever offsets are available. (I believe also using
+        // the first of the two tag pairs that's available—remember tags are encoded ascending).
+        let is_tiled = ifd.contains(Tag::TileWidth) || ifd.contains(Tag::TileLength);
+        let has_strips = ifd.contains(Tag::StripByteCounts) && ifd.contains(Tag::StripOffsets);
+        let has_tiles = ifd.contains(Tag::TileByteCounts) && ifd.contains(Tag::TileOffsets);
+
         let chunk_type;
         let chunk_offsets;
         let chunk_bytes;
         let strip_decoder;
         let tile_attributes;
-        match (
-            ifd.contains(Tag::StripByteCounts),
-            ifd.contains(Tag::StripOffsets),
-            ifd.contains(Tag::TileByteCounts),
-            ifd.contains(Tag::TileOffsets),
-        ) {
-            (true, true, false, false) => {
-                chunk_type = ChunkType::Strip;
 
-                chunk_offsets = tag_reader
-                    .find_tag(Tag::StripOffsets)?
-                    .unwrap()
-                    .into_u64_vec()?;
-                chunk_bytes = tag_reader
-                    .find_tag(Tag::StripByteCounts)?
-                    .unwrap()
-                    .into_u64_vec()?;
-                let rows_per_strip = tag_reader
-                    .find_tag(Tag::RowsPerStrip)?
-                    .map(Value::into_u32)
-                    .transpose()?
-                    .unwrap_or(height);
-                strip_decoder = Some(StripDecodeState { rows_per_strip });
-                tile_attributes = None;
+        if !is_tiled && has_strips {
+            chunk_type = ChunkType::Strip;
 
-                if chunk_offsets.len() != chunk_bytes.len() {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::InconsistentSizesEncountered,
-                    ));
-                }
+            chunk_offsets = tag_reader
+                .find_tag(Tag::StripOffsets)?
+                .unwrap()
+                .into_u64_vec()?;
+            chunk_bytes = tag_reader
+                .find_tag(Tag::StripByteCounts)?
+                .unwrap()
+                .into_u64_vec()?;
+            let rows_per_strip = tag_reader
+                .find_tag(Tag::RowsPerStrip)?
+                .map(Value::into_u32)
+                .transpose()?
+                .unwrap_or(height);
+            strip_decoder = Some(StripDecodeState { rows_per_strip });
+            tile_attributes = None;
 
-                if rows_per_strip == 0 {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::InconsistentSizesEncountered,
-                    ));
-                }
-
-                if u32::try_from(chunk_offsets.len())?
-                    != height.div_ceil(rows_per_strip) * planes as u32
-                {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::IncorrectChunkCount {
-                            expected: height.div_ceil(rows_per_strip) * planes as u32,
-                            found: chunk_offsets.len() as u32,
-                        },
-                    ));
-                }
-            }
-            (false, false, true, true) => {
-                chunk_type = ChunkType::Tile;
-
-                let tile_width =
-                    usize::try_from(tag_reader.require_tag(Tag::TileWidth)?.into_u32()?)?;
-                let tile_length =
-                    usize::try_from(tag_reader.require_tag(Tag::TileLength)?.into_u32()?)?;
-
-                if tile_width == 0 {
-                    return Err(TiffFormatError::InvalidTagValueType(Tag::TileWidth).into());
-                } else if tile_length == 0 {
-                    return Err(TiffFormatError::InvalidTagValueType(Tag::TileLength).into());
-                }
-
-                strip_decoder = None;
-                tile_attributes = Some(TileAttributes {
-                    image_width: usize::try_from(width)?,
-                    image_height: usize::try_from(height)?,
-                    tile_width,
-                    tile_length,
-                });
-                chunk_offsets = tag_reader
-                    .find_tag(Tag::TileOffsets)?
-                    .unwrap()
-                    .into_u64_vec()?;
-                chunk_bytes = tag_reader
-                    .find_tag(Tag::TileByteCounts)?
-                    .unwrap()
-                    .into_u64_vec()?;
-
-                let tile = tile_attributes.as_ref().unwrap();
-
-                if chunk_offsets.len() != chunk_bytes.len() {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::InconsistentSizesEncountered,
-                    ));
-                }
-
-                if chunk_offsets.len() != tile.tiles_down() * tile.tiles_across() * planes as usize
-                {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::IncorrectChunkCount {
-                            expected: (tile.tiles_down() * tile.tiles_across() * planes as usize)
-                                as u32,
-                            found: chunk_offsets.len() as u32,
-                        },
-                    ));
-                }
-            }
-            (_, _, _, _) => {
+            if chunk_offsets.len() != chunk_bytes.len() {
                 return Err(TiffError::FormatError(
-                    TiffFormatError::StripTileTagConflict,
-                ))
+                    TiffFormatError::InconsistentSizesEncountered,
+                ));
             }
+
+            if rows_per_strip == 0 {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::InconsistentSizesEncountered,
+                ));
+            }
+
+            if u32::try_from(chunk_offsets.len())?
+                != height.div_ceil(rows_per_strip) * planes as u32
+            {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::IncorrectChunkCount {
+                        expected: height.div_ceil(rows_per_strip) * planes as u32,
+                        found: chunk_offsets.len() as u32,
+                    },
+                ));
+            }
+        } else if is_tiled && (has_strips || has_tiles) {
+            chunk_type = ChunkType::Tile;
+
+            let tile_width = usize::try_from(tag_reader.require_tag(Tag::TileWidth)?.into_u32()?)?;
+            let tile_length =
+                usize::try_from(tag_reader.require_tag(Tag::TileLength)?.into_u32()?)?;
+
+            // Prioritize tiles over strips, tiles are what we expect.
+            let (tag_offsets, tag_counts) = if has_tiles {
+                (Tag::TileOffsets, Tag::TileByteCounts)
+            } else {
+                (Tag::StripOffsets, Tag::StripByteCounts)
+            };
+
+            if tile_width == 0 {
+                return Err(TiffFormatError::InvalidTagValueType(Tag::TileWidth).into());
+            } else if tile_length == 0 {
+                return Err(TiffFormatError::InvalidTagValueType(Tag::TileLength).into());
+            }
+
+            strip_decoder = None;
+            tile_attributes = Some(TileAttributes {
+                image_width: usize::try_from(width)?,
+                image_height: usize::try_from(height)?,
+                tile_width,
+                tile_length,
+            });
+
+            chunk_offsets = tag_reader.find_tag(tag_offsets)?.unwrap().into_u64_vec()?;
+            chunk_bytes = tag_reader.find_tag(tag_counts)?.unwrap().into_u64_vec()?;
+
+            let tile = tile_attributes.as_ref().unwrap();
+
+            if chunk_offsets.len() != chunk_bytes.len() {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::InconsistentSizesEncountered,
+                ));
+            }
+
+            if chunk_offsets.len() != tile.tiles_down() * tile.tiles_across() * planes as usize {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::IncorrectChunkCount {
+                        expected: (tile.tiles_down() * tile.tiles_across() * planes as usize)
+                            as u32,
+                        found: chunk_offsets.len() as u32,
+                    },
+                ));
+            }
+        } else {
+            return Err(TiffError::FormatError(
+                TiffFormatError::StripTileTagConflict,
+            ));
         };
 
         let mut sample_format = sample_format;

src/decoder/mod.rs

@@ -857,64 +857,11 @@ impl TiffHeader {
 }
 
 impl<R: Read + Seek> Decoder<R> {
-    /// Parse the image header from the underlying file and create a decoder positioned before its
-    /// first directory.
-    ///
-    /// This method opens the file in a state _before_ the first (image) directory. You need to
-    /// call one of [`Self::next_image`], [`Self::next_directory`] or [`Self::seek_to_directory`]
-    /// to choose a directory before interacting with the tag methods.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use tiff::decoder::{Decoder, DecodingResult};
-    ///
-    /// let buffered_file = /* */
-    /// # std::io::Cursor::new(include_bytes!(concat!(
-    /// #   env!("CARGO_MANIFEST_DIR"), "/tests/images/tiled-gray-i1.tif"
-    /// # )));
-    ///
-    /// let mut decoder =  Decoder::open(buffered_file)?;
-    /// let mut img_buffer = DecodingResult::U8(vec![]);
-    ///
-    /// while decoder.more_images() {
-    ///     decoder.next_image()?;
-    ///     decoder.read_image_to_buffer(&mut img_buffer)?;
-    /// }
-    ///
-    /// # Ok::<_, tiff::TiffError>(())
-    /// ```
-    ///
-    /// # Relations
-    ///
-    /// The [`TiffHeader`] type allows opening a file with a custom offset.
-    pub fn open(mut r: R) -> TiffResult<Decoder<R>> {
-        let header = TiffHeader::parse(&mut r)?;
-        Ok(header.open(r))
-    }
-
     /// Create a decoder and attempt to parse the first image directory.
     ///
     /// To open a file without parsing any directory yet (for instance to retain a [`Decoder`] on
-    /// errors in the directory), use [`TiffHeader::parse`] and [`TiffHeader::open`] instead.
-    ///
-    /// This method is equivalent to [`Decoder::open`] except it provides no decoder when the first
-    /// IFD errors due to not being an image or an IO problem. It can be replaced precisely with
-    /// this sequence:
-    ///
-    /// ```no_run
-    /// # use tiff::decoder::Decoder;
-    /// # let r = std::io::BufReader::new(std::io::empty());
-    /// let decoder = {
-    ///     let mut tmp = Decoder::open(r)?;
-    ///     tmp.next_image()?;
-    ///     tmp
-    /// };
-    ///
-    /// # Ok::<_, tiff::TiffError>(())
-    /// ```
-    ///
-    #[deprecated = "Prefer `Decoder::open` followed by an explicit `next_image` call. These methods will become aliases in a future major release."]
+    /// errors in the directory), use [`TiffHeader::parse`] and [`TiffHeader::open`] instead..
+    #[deprecated = "Prefer `Decoder::open`. These methods will become aliases in a future major release."]
     pub fn new(mut r: R) -> TiffResult<Decoder<R>> {
         let header = TiffHeader::parse(&mut r)?;
         let mut decoder = header.open(r);
@@ -922,6 +869,15 @@ impl<R: Read + Seek> Decoder<R> {
         Ok(decoder)
     }
 
+    /// Parse the image header from the underlying file and create a decoder positioned before its
+    /// first directory.
+    ///
+    /// The [`TiffHeader`] type allows opening a file with a custom.
+    pub fn open(mut r: R) -> TiffResult<Decoder<R>> {
+        let header = TiffHeader::parse(&mut r)?;
+        Ok(header.open(r))
+    }
+
     /// Configure allocation limits for all subsequent operations.
     ///
     /// Limits apply to allocated return values such as from [`Decoder::read_image`] and

tests/decode_libtiffpic.rs

@@ -12,9 +12,7 @@ const REFERENCE_DIR: &str = "tests/libtiffpic";
 const FILES: &[(&str, bool)] = &[
     ("tests/libtiffpic/caspian.tif", true),
     ("tests/libtiffpic/cramps.tif", true),
-    // FIXME: See <https://github.com/image-rs/image-tiff/issues/338>, this has tiles as
-    // StripOffsets and has a RowsPerStrip.
-    ("tests/libtiffpic/cramps-tile.tif", false),
+    ("tests/libtiffpic/cramps-tile.tif", true),
     ("tests/libtiffpic/CVS/Entries", false),
     ("tests/libtiffpic/CVS/Repository", false),
     ("tests/libtiffpic/CVS/Root", false),
@@ -90,9 +88,7 @@ const FILES: &[(&str, bool)] = &[
     ("tests/libtiffpic/pc260001.tif", true),
     ("tests/libtiffpic/quad-jpeg.tif", true),
     ("tests/libtiffpic/quad-lzw.tif", true),
-    // FIXME: See <https://github.com/image-rs/image-tiff/issues/338>, this has tiles as
-    // StripOffsets and has a RowsPerStrip.
-    ("tests/libtiffpic/quad-tile.tif", false),
+    ("tests/libtiffpic/quad-tile.tif", true),
     ("tests/libtiffpic/README", false),
     ("tests/libtiffpic/smallliz.tif", true),
     ("tests/libtiffpic/strike.tif", true),