From 0c65e13a4ec6becac842f3fda5c4bca92913f97a Mon Sep 17 00:00:00 2001
From: "WINDEV2110EVAL\\User" <jubilant-enigma@private.com>
Date: Mon, 6 Dec 2021 21:40:26 -0800
Subject: [PATCH] Don't save the exif text chunk if it is successfully parsed

---
 src/ImageSharp/Formats/Png/PngDecoderCore.cs  | 27 +++++++++++--------
 .../Formats/Png/PngMetadataTests.cs           |  6 ++++-
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index 236c447ab..436e706e8 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -976,12 +976,16 @@ namespace SixLabors.ImageSharp.Formats.Png
 
             if (this.TryUncompressTextData(compressedData, PngConstants.Encoding, out string uncompressed))
             {
-                metadata.TextData.Add(new PngTextData(name, uncompressed, string.Empty, string.Empty));
-            }
-
-            if (name.Equals("Raw profile type exif", StringComparison.OrdinalIgnoreCase))
-            {
-                this.ReadLegacyExifTextChunk(baseMetadata, uncompressed);
+                if (name.Equals("Raw profile type exif", StringComparison.OrdinalIgnoreCase) &&
+                    this.TryReadLegacyExifTextChunk(baseMetadata, uncompressed))
+                {
+                    // Successfully parsed exif data stored as text in this chunk
+                }
+                else
+                {
+                    // Seems to be regular old text data, or we failed to parse it in any special way
+                    metadata.TextData.Add(new PngTextData(name, uncompressed, string.Empty, string.Empty));
+                }
             }
         }
 
@@ -992,7 +996,7 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// </summary>
         /// <param name="metadata">The <see cref="ImageMetadata"/> to store the decoded exif tags into.</param>
         /// <param name="data">The contents of the "raw profile type exif" text chunk.</param>
-        private void ReadLegacyExifTextChunk(ImageMetadata metadata, string data)
+        private bool TryReadLegacyExifTextChunk(ImageMetadata metadata, string data)
         {
             ReadOnlySpan<char> dataSpan = data.AsSpan();
             dataSpan = dataSpan.TrimStart();
@@ -1000,7 +1004,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             if (!StringEquals(dataSpan.Slice(0, 4), "exif".AsSpan(), StringComparison.OrdinalIgnoreCase))
             {
                 // "exif" identifier is missing from the beginning of the text chunk
-                return;
+                return false;
             }
 
             // Skip to the data length
@@ -1014,7 +1018,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             if (dataLength < ExifHeader.Length)
             {
                 // Not enough room for the required exif header, this data couldn't possibly be valid
-                return;
+                return false;
             }
 
             // Parse the hex-encoded data into the byte array we are going to hand off to ExifProfile
@@ -1034,7 +1038,7 @@ namespace SixLabors.ImageSharp.Formats.Png
                 if (!tempExifBuf.AsSpan().Slice(0, ExifHeader.Length).SequenceEqual(ExifHeader))
                 {
                     // Exif header in the hex data is not valid
-                    return;
+                    return false;
                 }
 
                 // Skip over the exif header we just tested
@@ -1059,10 +1063,11 @@ namespace SixLabors.ImageSharp.Formats.Png
             }
             catch
             {
-                return;
+                return false;
             }
 
             this.MergeOrSetExifProfile(metadata, new ExifProfile(exifBlob), replaceExistingKeys: false);
+            return true;
         }
 
         private static bool StringEquals(ReadOnlySpan<char> span1, ReadOnlySpan<char> span2, StringComparison comparisonType)
diff --git a/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs
index d763d2ba0..8db1d1aaf 100644
--- a/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs
@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -300,8 +301,11 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
                 IImageInfo imageInfo = Image.Identify(stream);
                 Assert.NotNull(imageInfo);
                 Assert.NotNull(imageInfo.Metadata.ExifProfile);
-                ExifProfile exif = imageInfo.Metadata.ExifProfile;
 
+                PngMetadata meta = imageInfo.Metadata.GetFormatMetadata(PngFormat.Instance);
+                Assert.DoesNotContain(meta.TextData, t => t.Keyword.Equals("Raw profile type exif", StringComparison.OrdinalIgnoreCase));
+
+                ExifProfile exif = imageInfo.Metadata.ExifProfile;
                 Assert.Equal(0, exif.InvalidTags.Count);
                 Assert.Equal(3, exif.Values.Count);