Add support for OpenEXR image format by brianpopow · Pull Request #3096 · SixLabors/ImageSharp

brianpopow · 2026-03-29T18:12:31Z

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I have written a descriptive pull-request title
I have verified that there are no overlapping pull-requests open
I have verified that I am following the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
I have provided test coverage for my change (where applicable)

Description

This PR adds support for decoding and encoding of images in the OpenEXR format. OpenEXR is a HDR image format, therefore I have added two new pixel formats Rgb96 and Rgba128 which store each color channel as UInt32.

The specification can be found here: https://openexr.com/en/latest/index.html#openexr

A reference implementation can be found here: https://github.com/AcademySoftwareFoundation/openexr.git

# Conflicts: # src/ImageSharp/Configuration.cs

# Conflicts: # src/ImageSharp/Formats/Bmp/BmpConstants.cs # src/ImageSharp/Formats/Bmp/BmpDecoder.cs # src/ImageSharp/Formats/Bmp/BmpFormat.cs

# Conflicts: # src/ImageSharp/Configuration.cs # src/ImageSharp/Formats/Bmp/BmpArrayFileHeader.cs # src/ImageSharp/Formats/Bmp/BmpConstants.cs # src/ImageSharp/Formats/Bmp/BmpFormat.cs # src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs # src/ImageSharp/Formats/ImageExtensions.Save.cs # src/ImageSharp/Formats/Pbm/BufferedReadStreamExtensions.cs # tests/ImageSharp.Tests/ConfigurationTests.cs # tests/ImageSharp.Tests/Formats/GeneralFormatTests.cs

# Conflicts: # src/ImageSharp/Configuration.cs # src/ImageSharp/Formats/Bmp/BmpArrayFileHeader.cs # src/ImageSharp/Formats/Bmp/BmpConstants.cs # src/ImageSharp/Formats/Bmp/BmpDecoder.cs # src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs # src/ImageSharp/Formats/Bmp/BmpFileHeader.cs # src/ImageSharp/Formats/Bmp/BmpFormat.cs # src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs # src/ImageSharp/Formats/Bmp/BmpInfoHeader.cs # src/ImageSharp/Formats/ImageDecoderUtilities.cs # src/ImageSharp/Formats/ImageExtensions.Save.cs # src/ImageSharp/Formats/Pbm/BufferedReadStreamExtensions.cs # src/ImageSharp/Image.Decode.cs # tests/ImageSharp.Tests/ConfigurationTests.cs # tests/ImageSharp.Tests/Formats/GeneralFormatTests.cs

# Conflicts: # src/ImageSharp/Formats/Bmp/BmpFormat.cs # src/ImageSharp/Formats/ImageDecoderUtilities.cs # src/ImageSharp/Formats/ImageExtensions.Save.cs # src/ImageSharp/Formats/OpenExr/ExrDecoderCore.cs

# Conflicts: # src/ImageSharp/Configuration.cs # src/ImageSharp/Formats/ImageDecoderUtilities.cs # tests/ImageSharp.Tests/TestUtilities/TestEnvironment.Formats.cs

JimBobSquarePants · 2026-04-06T13:28:59Z

src/ImageSharp/PixelFormats/PixelImplementations/Rgba128.cs

+            PixelAlphaRepresentation.Unassociated);
+
+    /// <inheritdoc/>
+    public readonly Rgba32 ToRgba32() => throw new NotImplementedException();


We need to implement all these.

this is now implemented

JimBobSquarePants · 2026-04-06T13:31:53Z

tests/Directory.Build.targets

    See https://github.com/ImageMagick/ImageMagick/commit/27a0a9c37f18af9c8d823a3ea076f600843b553c
    -->
-    <PackageReference Update="Magick.NET-Q16-AnyCPU" Version="13.10.0" />
+    <PackageReference Update="Magick.NET-Q16-AnyCPU" Version="14.11.1" />


Oh, you got this working!! Fantastic!! 🙌

I had to upgrade to the latest version of Magick.NET, because of an issue decoding some exr files, which was fixed here

Unfortunately this also changed how some bitmaps which are RLE compressed are decoded. I had to change some testcases to use CompareToReferenceOutput instead of using the reference decoder: 0c3ca3d

I'm absolutely fine with CompareToReferenceOutput . Our decoder is rock solid now and that should be enough to protect against regression.

JimBobSquarePants · 2026-04-06T13:33:07Z

src/ImageSharp/Formats/Exr/Compression/Compressors/ZipExrCompressor.cs

+        for (int i = 1; i < predicted.Length; i++)
+        {
+            int d = (predicted[i] - p + 128 + 256) & 255;
+            p = predicted[i];


You can use ref here

JimBobSquarePants · 2026-04-06T13:34:09Z

src/ImageSharp/Formats/Exr/Compression/Decompressors/ZipExrCompression.cs

+
+        if (totalRead == 0)
+        {
+            ExrThrowHelper.ThrowInvalidImageContentException("Could not read zip compressed image data!");


I wonder if we should just break here? Normally we try to return as much pixel information as we can.

JimBobSquarePants · 2026-04-06T13:36:19Z

src/ImageSharp/Formats/Exr/Compression/ExrBaseDecompressor.cs

+
+namespace SixLabors.ImageSharp.Formats.Exr.Compression;
+
+internal abstract class ExrBaseDecompressor : ExrBaseCompression


I know these types are internal but I'm finding it very useful currently to document the crap out of everything (AI really helps here.)

brianpopow · 2026-04-07T09:20:08Z

@brianpopow I'll be able to focus on a proper review this week.

@JimBobSquarePants: dont worry keep your time, it is not urgent.

Just as a heads up: I noticed issues with the pixel conversion methods introduced with the new pixel types. I am trying to add tests for them in the next days. Those conversion methods will change, so maybe exclude them from a review until then, because they will change anyway.

tests/ImageSharp.Tests/PixelFormats/Rgb96Tests.cs

tests/ImageSharp.Tests/PixelFormats/Rgba128Tests.cs

JimBobSquarePants · 2026-04-10T00:38:02Z

...t/BmpDecoderTests/BmpDecoder_CanDecode_RunLengthEncoded_4Bit_WithDelta_Rgba32_pal4rlecut.png

This output looks bugged to me. Has the Magick comparison been hiding an issue?

The image looks like this:

The image is from the bmp suite where alot of the edge case image in the tests come from.

From the description of the image:

An RLE-compressed image that uses “delta” codes, and early EOL & EOBMP markers, to skip over some pixels. It’s okay if the viewer’s image doesn’t exactly match any of the reference images.

It looks like the third image in the "correct display" list: the undefined pixels are black.

src/ImageSharp/Formats/Exr/ExrDecoderCore.cs

…r4 was not used

brianpopow added 30 commits December 26, 2021 11:24

Parse open EXR header

9dda678

Decode uncompressed EXR images with 16 bit pixel data for each channel

a27696a

Decode EXR images with 32 bit float pixel data

d3993f7

Decode EXR images with unsigned int pixel data

aaf2143

Encode EXR image with float pixel data

799dafe

Encode EXR image with HalfSingle pixel data

4cf95a5

Encode EXR image with usigned int pixel data

7e7472d

Update tests for EXR images

652b385

Add support for decoding EXR images with alpha channel

70cfcc9

Add support for decoding exr with zips compression

3279762

Add support for decoding RLE exr images

85501f3

Add support for ZIP compressed exr images

69c8cd8

Add support for decoding gray exr images

fdc7b61

Refactor

fd0c245

Merge remote-tracking branch 'origin/main' into bp/openExr

88a06e8

# Conflicts: # src/ImageSharp/Configuration.cs

Merge remote-tracking branch 'origin/main' into bp/openExr

aabe561

# Conflicts: # src/ImageSharp/Formats/Bmp/BmpConstants.cs # src/ImageSharp/Formats/Bmp/BmpDecoder.cs # src/ImageSharp/Formats/Bmp/BmpFormat.cs

Fix build errors

ea1aaa7

Add exr decoder tests

ce21f1a

Add support for decoding b44 compressed exr files

a9620ee

Fix warnings

ec8163a

Add DecodeTiledFloatingPointPixelData

28dcdf2

Merge remote-tracking branch 'origin/bp/openExr' into bp/openExr

d0d5e86

# Conflicts: # src/ImageSharp/Formats/Bmp/BmpFormat.cs # src/ImageSharp/Formats/ImageDecoderUtilities.cs # src/ImageSharp/Formats/ImageExtensions.Save.cs # src/ImageSharp/Formats/OpenExr/ExrDecoderCore.cs

Merge branch 'main' into bp/openExr

7748467

# Conflicts: # src/ImageSharp/Configuration.cs # src/ImageSharp/Formats/ImageDecoderUtilities.cs # tests/ImageSharp.Tests/TestUtilities/TestEnvironment.Formats.cs

Adjust exr decoder / encoder to ImageSharp changes

fa52ab7

Change exr name space to SixLabors.ImageSharp.Formats.Exr

83dba58

Fix issue in ExrImageFormatDetector.cs returning wrong format

b78402d

Use MagickReference decoder for exr decoding tests

faf87fb

Fix issue assigning pixel value from HalfVector4

eaea042

JimBobSquarePants reviewed Apr 6, 2026

View reviewed changes

Merge branch 'main' into bp/openExr

05c89f7

brianpopow and others added 3 commits April 7, 2026 18:03

Add tests for Rgb96 pixel conversions

d1623fe

Try fix issues with Rgb96 pixel conversions

787ebb2

Merge branch 'main' into bp/openExr

3fbf0ef

github-code-quality bot found potential problems Apr 7, 2026

View reviewed changes

tests/ImageSharp.Tests/PixelFormats/Rgb96Tests.cs Fixed Show fixed Hide fixed

Add null check for PixelComponentInfo in Rgb96_PixelInformation()

0ec523f

github-code-quality bot found potential problems Apr 7, 2026

View reviewed changes

tests/ImageSharp.Tests/PixelFormats/Rgb96Tests.cs Dismissed Show dismissed Hide dismissed

brianpopow and others added 3 commits April 8, 2026 19:07

Add tests for Rgba128

e611b1e

Fix issues with pixel conversions in Rgba128

24dbf63

Merge branch 'main' into bp/openExr

2abbedc

github-code-quality bot found potential problems Apr 8, 2026

View reviewed changes

tests/ImageSharp.Tests/PixelFormats/Rgba128Tests.cs Dismissed Show dismissed Hide dismissed

Merge branch 'main' into bp/openExr

fb32977

JimBobSquarePants reviewed Apr 10, 2026

View reviewed changes

JimBobSquarePants mentioned this pull request Apr 10, 2026

Disabled RLE BMP tests #3112

Closed

brianpopow added 3 commits April 11, 2026 19:35

Better test image for uint pixel type

51463a3

Remove unnecessary ColorScaleTo32Bit when decoding pixel type uint32

b4cd27f

Remove ExrCompression property from ExrBaseCompression, it is not needed

5926455

github-code-quality bot found potential problems Apr 11, 2026

View reviewed changes

src/ImageSharp/Formats/Exr/ExrDecoderCore.cs Fixed Show fixed Hide fixed

brianpopow and others added 6 commits April 12, 2026 17:13

Remove no longer needed ColorScaleTo32Bit()

0ceeba4

Add test case for uint pixel type with alpha

29f558a

Merge branch 'main' into bp/openExr

b15625e

Fix mistake when encoding uint pixel data: value from Rgb96.FromVecto…

3722997

…r4 was not used

Write alpha channel when encoding exr images

15701e5

Add better test image for uint rgba pixel type

af14463


		namespace SixLabors.ImageSharp.Formats.Exr.Compression;

		internal abstract class ExrBaseDecompressor : ExrBaseCompression

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brianpopow commented Apr 7, 2026

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brianpopow commented Mar 29, 2026 •

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