From 0b55bed262d75aac144e295bf83b98d1cb3ae142 Mon Sep 17 00:00:00 2001
From: Dmitry Pentin <riotbr3aker@gmail.com>
Date: Tue, 7 Sep 2021 04:12:56 +0300
Subject: [PATCH] Slightly improved tiff decoding with jpeg data, removed
 unnecessary GC pressure

---
 .../Jpeg/Components/Decoder/SpectralConverter.cs      |  2 +-
 .../Compression/Decompressors/JpegTiffCompression.cs  | 11 +++++------
 .../Decompressors/RgbJpegSpectralConverter.cs         |  2 +-
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/ImageSharp/Formats/Jpeg/Components/Decoder/SpectralConverter.cs b/src/ImageSharp/Formats/Jpeg/Components/Decoder/SpectralConverter.cs
index 23bb01409c..e975b11fbb 100644
--- a/src/ImageSharp/Formats/Jpeg/Components/Decoder/SpectralConverter.cs
+++ b/src/ImageSharp/Formats/Jpeg/Components/Decoder/SpectralConverter.cs
@@ -39,6 +39,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <param name="frame">The jpeg frame with the color space to convert to.</param>
         /// <param name="jpegData">The raw JPEG data.</param>
         /// <returns>The color converter.</returns>
-        public virtual JpegColorConverter GetColorConverter(JpegFrame frame, IRawJpegData jpegData) => JpegColorConverter.GetConverter(jpegData.ColorSpace, frame.Precision);
+        protected virtual JpegColorConverter GetColorConverter(JpegFrame frame, IRawJpegData jpegData) => JpegColorConverter.GetConverter(jpegData.ColorSpace, frame.Precision);
     }
 }
diff --git a/src/ImageSharp/Formats/Tiff/Compression/Decompressors/JpegTiffCompression.cs b/src/ImageSharp/Formats/Tiff/Compression/Decompressors/JpegTiffCompression.cs
index bd1c496b49..e764c014d3 100644
--- a/src/ImageSharp/Formats/Tiff/Compression/Decompressors/JpegTiffCompression.cs
+++ b/src/ImageSharp/Formats/Tiff/Compression/Decompressors/JpegTiffCompression.cs
@@ -65,22 +65,21 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
                 scanDecoder.ResetInterval = 0;
                 jpegDecoder.ParseStream(stream, scanDecoder, CancellationToken.None);
 
-                using var image = new Image<Rgb24>(this.configuration, spectralConverter.PixelBuffer, new ImageMetadata());
-                CopyImageBytesToBuffer(buffer, image);
+                CopyImageBytesToBuffer(buffer, spectralConverter.PixelBuffer);
             }
             else
             {
                 using var image = Image.Load<Rgb24>(stream);
-                CopyImageBytesToBuffer(buffer, image);
+                CopyImageBytesToBuffer(buffer, image.Frames.RootFrame.PixelBuffer);
             }
         }
 
-        private static void CopyImageBytesToBuffer(Span<byte> buffer, Image<Rgb24> image)
+        private static void CopyImageBytesToBuffer(Span<byte> buffer, Buffer2D<Rgb24> pixelBuffer)
         {
             int offset = 0;
-            for (int y = 0; y < image.Height; y++)
+            for (int y = 0; y < pixelBuffer.Height; y++)
             {
-                Span<Rgb24> pixelRowSpan = image.GetPixelRowSpan(y);
+                Span<Rgb24> pixelRowSpan = pixelBuffer.GetRowSpan(y);
                 Span<byte> rgbBytes = MemoryMarshal.AsBytes(pixelRowSpan);
                 rgbBytes.CopyTo(buffer.Slice(offset));
                 offset += rgbBytes.Length;
diff --git a/src/ImageSharp/Formats/Tiff/Compression/Decompressors/RgbJpegSpectralConverter.cs b/src/ImageSharp/Formats/Tiff/Compression/Decompressors/RgbJpegSpectralConverter.cs
index 45be3dd038..aefec7fa34 100644
--- a/src/ImageSharp/Formats/Tiff/Compression/Decompressors/RgbJpegSpectralConverter.cs
+++ b/src/ImageSharp/Formats/Tiff/Compression/Decompressors/RgbJpegSpectralConverter.cs
@@ -28,6 +28,6 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
         }
 
         /// <inheritdoc/>
-        public override JpegColorConverter GetColorConverter(JpegFrame frame, IRawJpegData jpegData) => JpegColorConverter.GetConverter(JpegColorSpace.RGB, frame.Precision);
+        protected override JpegColorConverter GetColorConverter(JpegFrame frame, IRawJpegData jpegData) => JpegColorConverter.GetConverter(JpegColorSpace.RGB, frame.Precision);
     }
 }