Read resolution from EXIF metadata in WebP

SixLabors · Nov 30, 2023 · f74b6ac · f74b6ac
1 parent 0d1296f
commit f74b6ac
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Showing 2 changed files with 54 additions and 1 deletion.
diff --git a/src/ImageSharp/Formats/Webp/WebpDecoderCore.cs b/src/ImageSharp/Formats/Webp/WebpDecoderCore.cs
@@ -3,6 +3,7 @@
 
 using System.Buffers;
 using System.Buffers.Binary;
+using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats.Webp.Lossless;
 using SixLabors.ImageSharp.Formats.Webp.Lossy;
 using SixLabors.ImageSharp.IO;
@@ -339,10 +340,33 @@ private void ReadExifProfile(BufferedReadStream stream, ImageMetadata metadata,
                 return;
             }
 
-            metadata.ExifProfile = new ExifProfile(exifData);
+            ExifProfile exifProfile = new(exifData);
+
+            // Set the resolution from the metadata.
+            double horizontalValue = GetExifResolutionValue(exifProfile, ExifTag.XResolution);
+            double verticalValue = GetExifResolutionValue(exifProfile, ExifTag.YResolution);
+
+            if (horizontalValue > 0 && verticalValue > 0)
+            {
+                metadata.HorizontalResolution = horizontalValue;
+                metadata.VerticalResolution = verticalValue;
+                metadata.ResolutionUnits = UnitConverter.ExifProfileToResolutionUnit(exifProfile);
+            }
+
+            metadata.ExifProfile = exifProfile;
         }
     }
 
+    private static double GetExifResolutionValue(ExifProfile exifProfile, ExifTag<Rational> tag)
+    {
+        if (exifProfile.TryGetValue(tag, out IExifValue<Rational>? resolution))
+        {
+            return resolution.Value.ToDouble();
+        }
+
+        return 0;
+    }
+
     /// <summary>
     /// Reads the XMP profile the stream.
     /// </summary>

diff --git a/tests/ImageSharp.Tests/Formats/WebP/WebpDecoderTests.cs b/tests/ImageSharp.Tests/Formats/WebP/WebpDecoderTests.cs
@@ -4,6 +4,7 @@
 using System.Runtime.Intrinsics.X86;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Webp;
+using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Tests.TestUtilities;
 using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
@@ -493,4 +494,32 @@ private static void RunDecodeLossyWithComplexFilterTest()
 
     [Fact]
     public void DecodeLossyWithComplexFilterTest_WithoutHardwareIntrinsics_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunDecodeLossyWithComplexFilterTest, HwIntrinsics.DisableHWIntrinsic);
+
+    [Theory]
+    [InlineData(Lossy.BikeWithExif)]
+    public void Decode_VerifyRatio(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using MemoryStream stream = new(testFile.Bytes, false);
+        using Image image = WebpDecoder.Instance.Decode(DecoderOptions.Default, stream);
+        ImageMetadata meta = image.Metadata;
+
+        Assert.Equal(37.8, meta.HorizontalResolution);
+        Assert.Equal(37.8, meta.VerticalResolution);
+        Assert.Equal(PixelResolutionUnit.PixelsPerCentimeter, meta.ResolutionUnits);
+    }
+
+    [Theory]
+    [InlineData(Lossy.BikeWithExif)]
+    public void Identify_VerifyRatio(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using MemoryStream stream = new(testFile.Bytes, false);
+        ImageInfo image = WebpDecoder.Instance.Identify(DecoderOptions.Default, stream);
+        ImageMetadata meta = image.Metadata;
+
+        Assert.Equal(37.8, meta.HorizontalResolution);
+        Assert.Equal(37.8, meta.VerticalResolution);
+        Assert.Equal(PixelResolutionUnit.PixelsPerCentimeter, meta.ResolutionUnits);
+    }
 }