Merge fix_endianness and rev_hpredict methods

src/decoder/image.rs

@@ -399,7 +399,15 @@ impl Image {
             | (ColorType::CMYK(n), _)
             | (ColorType::Gray(n), _)
                 if usize::from(n) == buffer.byte_len() * 8 => {}
-            (ColorType::Gray(n), DecodingBuffer::U8(_)) if n <= 8 => {}
+            (ColorType::Gray(n), DecodingBuffer::U8(_)) if n < 8 => match self.predictor {
+                Predictor::None => {}
+                Predictor::Horizontal => {
+                    return Err(TiffError::UnsupportedError(
+                        TiffUnsupportedError::HorizontalPredictor(color_type),
+                    ))
+                }
+                Predictor::__NonExhaustive => unreachable!(),
+            },
             (type_, _) => {
                 return Err(TiffError::UnsupportedError(
                     TiffUnsupportedError::UnsupportedColorType(type_),
@@ -407,6 +415,17 @@ impl Image {
             }
         }
 
+        // Validate that the predictor is supported for the sample type.
+        match (self.predictor, &buffer) {
+            (Predictor::Horizontal, DecodingBuffer::F32(_))
+            | (Predictor::Horizontal, DecodingBuffer::F64(_)) => {
+                return Err(TiffError::UnsupportedError(
+                    TiffUnsupportedError::HorizontalPredictor(color_type),
+                ));
+            }
+            _ => {}
+        }
+
         let compressed_bytes = self.chunk_bytes.get(chunk).ok_or(TiffError::FormatError(
             TiffFormatError::InconsistentSizesEncountered,
         ))?;
@@ -443,7 +462,12 @@ impl Image {
             let tile = &mut buffer.as_bytes_mut()[..total_samples * byte_len];
             reader.read_exact(tile)?;
 
-            super::fix_endianness(&mut buffer.subrange(0..total_samples), byte_order);
+            for row in 0..(chunk_dimensions.1 - padding.1) {
+                let row_start = row * output_width * samples;
+                let row_end = (row + 1) * output_width * samples;
+                let row = buffer.subrange(row_start..row_end);
+                super::fix_endianness_and_predict(row, samples, byte_order, predictor);
+            }
             if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
                 super::invert_colors(&mut buffer.subrange(0..total_samples), color_type);
             }
@@ -461,29 +485,14 @@ impl Image {
                     io::copy(&mut reader.by_ref().take(len), &mut io::sink())?;
                 }
 
-                super::fix_endianness(&mut buffer.subrange(row_start..row_end), byte_order);
+                let mut row = buffer.subrange(row_start..row_end);
+                super::fix_endianness_and_predict(row.copy(), samples, byte_order, predictor);
                 if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
-                    super::invert_colors(&mut buffer.subrange(row_start..row_end), color_type);
+                    super::invert_colors(&mut row, color_type);
                 }
             }
         }
 
-        match predictor {
-            Predictor::None => {}
-            Predictor::Horizontal => {
-                super::rev_hpredict(
-                    buffer,
-                    (
-                        u32::try_from(chunk_dimensions.0 - padding.0)?,
-                        u32::try_from(chunk_dimensions.1 - padding.1)?,
-                    ),
-                    output_width,
-                    color_type,
-                )?;
-            }
-            Predictor::__NonExhaustive => unreachable!(),
-        }
-
         Ok(())
     }
 }