review changes: pass in width/height, unwrap reader bytes

src/decoder/image.rs

@@ -381,7 +381,8 @@ impl Image {
     }
 
     fn create_reader<'r, R: 'r + Read>(
-        &self,
+        width: u32,
+        height: u32,
         reader: R,
         compression_method: CompressionMethod,
         compressed_length: u64,
@@ -454,22 +455,24 @@ impl Image {
                 Box::new(Cursor::new(data))
             }
             CompressionMethod::Fax4 => {
-                let width = u16::try_from(self.width)?;
+                let width = u16::try_from(width)?;
-                let height = u16::try_from(self.height)?;
+                let height = u16::try_from(height)?;
                 let mut out: Vec<u8> = Vec::with_capacity(usize::from(width) * usize::from(height));
 
-                let mut buffer = Vec::with_capacity(usize::try_from(compressed_length)?);
-                reader.take(compressed_length).read_to_end(&mut buffer)?;
-
                 // all extant tiff/fax4 decoders I've found always assume that the photometric interpretation
                 // is `WhiteIsZero`, ignoring the tag. ImageMagick appears to generate fax4-encoded tiffs
                 // with the tag incorrectly set to `BlackIsZero`.
-                fax::decoder::decode_g4(buffer.into_iter(), width, Some(height), |transitions| {
+                fax::decoder::decode_g4(
-                    out.extend(fax::decoder::pels(transitions, width).map(|c| match c {
+                    reader.bytes().map(|b| b.unwrap()),
-                        fax::Color::Black => 255,
+                    width,
-                        fax::Color::White => 0,
+                    Some(height),
-                    }))
+                    |transitions| {
-                });
+                        out.extend(fax::decoder::pels(transitions, width).map(|c| match c {
+                            fax::Color::Black => 255,
+                            fax::Color::White => 0,
+                        }))
+                    },
+                );
                 Box::new(Cursor::new(out))
             }
             method => {
@@ -673,7 +676,9 @@ impl Image {
         assert!(output_row_stride >= data_row_bytes);
         assert!(buf.len() >= output_row_stride * (data_dims.1 as usize - 1) + data_row_bytes);
 
-        let mut reader = self.create_reader(
+        let mut reader = Self::create_reader(
+            self.width,
+            self.height,
             reader,
             compression_method,
             *compressed_bytes,