Merge pull request #272 from Enet4/imp/lossless-bitdepth

Admit more precision values in JPEG Lossless

benches/decoding_benchmark.rs

@@ -35,7 +35,7 @@ fn main() {
     }));
 
     c.bench_function("decode a 3072x2048 RGB Lossless JPEG", |b| b.iter(|| {
-        read_image(include_bytes!("../tests/reftest/images/lossless/jpeg_lossless_sel1-rgb.jpg"))
+        read_image(include_bytes!("../tests/reftest/images/lossless/1/jpeg_lossless_sel1-rgb.jpg"))
     }));
     c.final_summary();
 }

src/decoder.rs

@@ -173,8 +173,8 @@ impl<R: Read> Decoder<R> {
             Some(ref frame) => {
                 let pixel_format = match frame.components.len() {
                     1 => match frame.precision {
-                        8 => PixelFormat::L8,
-                        16 => PixelFormat::L16,
+                        2..=8 => PixelFormat::L8,
+                        9..=16 => PixelFormat::L16,
                         _ => panic!(),
                     },
                     3 => PixelFormat::RGB24,
@@ -360,7 +360,7 @@ impl<R: Read> Decoder<R> {
                             frame.precision,
                         )));
                     }
-                    if frame.precision != 8 && frame.precision != 16 {
+                    if !(2..=16).contains(&frame.precision) {
                         return Err(Error::Unsupported(UnsupportedFeature::SamplePrecision(
                             frame.precision,
                         )));

tests/reftest/images/lossless/1/README.md

@@ -0,0 +1,5 @@
+# JPEG Lossless data set 1
+
+The files starting with jpeg_lossless were taken from <https://github.com/rii-mango/JPEGLosslessDecoderJS>.
+The image data bytes were extracted from the DICOM files.
+The reference PNG files were created with the IJG library as distributed in the GDCM toolkit <https://github.com/malaterre/GDCM/tree/master/Utilities/gdcmjpeg>.

tests/reftest/images/lossless/2/README.md

@@ -0,0 +1,18 @@
+# JPEG Lossless data set 2
+
+The JPEG losssless files in this data set
+were collected from the DICOM-WG04 compilation of public DICOM files in
+<ftp://medical.nema.org/medical/dicom/DataSets/WG04> (revision 2004/08/26),
+extracting the JPEG data from the files' pixel data.
+
+The ground truth was collected from the respective reference (uncompressed) files
+and converted to 16-bit PNG files.
+
+## Description
+
+- **MR4**: 512x512, 12 bit precision, non-hierarchical, selection value 1
+  - JPEG extracted from DICOM file `JPLL/MR4_JPLL`
+  - Ground truth converted from DICOM file `REF/MR4_UNC`
+- **XA1**: 1024x1024, 10 bit precision, non-hierarchical, selection value 1
+  - JPEG extracted from DICOM file `JPLL/XA1_JPLL`
+  - Ground truth converted from DICOM file `REF/XA1_UNC`