Add additional chunk types

src/ImageSharp/Formats/Png/PngChunkType.cs

@@ -73,6 +73,58 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// either alpha values associated with palette entries (for indexed-color images)
         /// or a single transparent color (for grayscale and true color images).
         /// </summary>
-        Transparency = 0x74524E53U
+        Transparency = 0x74524E53U,
+
+        /// <summary>
+        /// The tIME chunk gives the time of the last image modification (not the time of initial image creation).
+        /// </summary>
+        Time = 0x74494d45,
+
+        /// <summary>
+        /// The bKGD chunk specifies a default background colour to present the image against.
+        /// If there is any other preferred background, either user-specified or part of a larger page (as in a browser),
+        /// the bKGD chunk should be ignored.
+        /// </summary>
+        Background = 0x624b4744,
+
+        /// <summary>
+        /// The iCCP chunk contains a embedded color profile. If the iCCP chunk is present,
+        /// the image samples conform to the colour space represented by the embedded ICC profile as defined by the International Color Consortium.
+        /// </summary>
+        EmbeddedColorProfile = 0x69434350,
+
+        /// <summary>
+        /// The sBIT chunk defines the original number of significant bits (which can be less than or equal to the sample depth).
+        /// This allows PNG decoders to recover the original data losslessly even if the data had a sample depth not directly supported by PNG.
+        /// </summary>
+        SignificantBits = 0x73424954,
+
+        /// <summary>
+        /// If the sRGB chunk is present, the image samples conform to the sRGB colour space [IEC 61966-2-1] and should be displayed
+        /// using the specified rendering intent defined by the International Color Consortium.
+        /// </summary>
+        StandardRgbColourSpace = 0x73524742,
+
+        /// <summary>
+        /// The hIST chunk gives the approximate usage frequency of each colour in the palette.
+        /// </summary>
+        Histogram = 0x68495354,
+
+        /// <summary>
+        /// The sPLT chunk contains the suggested palette.
+        /// </summary>
+        SuggestedPalette = 0x73504c54,
+
+        /// <summary>
+        /// The cHRM chunk may be used to specify the 1931 CIE x,y chromaticities of the red,
+        /// green, and blue display primaries used in the image, and the referenced white point.
+        /// </summary>
+        Chroma = 0x6348524d,
+
+        /// <summary>
+        /// Malformed chunk named CgBI produced by apple, which is not conform to the specification.
+        /// Related issue is here https://github.com/SixLabors/ImageSharp/issues/410
+        /// </summary>
+        MalformedApple = 0x43674249
     }
 }

tests/ImageSharp.Tests/Formats/Png/PngChunkTypeTests.cs

@@ -19,9 +19,20 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
             Assert.Equal(PngChunkType.End, GetType("IEND"));
             Assert.Equal(PngChunkType.Transparency, GetType("tRNS"));
             Assert.Equal(PngChunkType.Text, GetType("tEXt"));
+            Assert.Equal(PngChunkType.InternationalText, GetType("iTXt"));
+            Assert.Equal(PngChunkType.CompressedText, GetType("zTXt"));
+            Assert.Equal(PngChunkType.Chroma, GetType("cHRM"));
             Assert.Equal(PngChunkType.Gamma, GetType("gAMA"));
             Assert.Equal(PngChunkType.Physical, GetType("pHYs"));
             Assert.Equal(PngChunkType.Exif, GetType("eXIf"));
+            Assert.Equal(PngChunkType.Time, GetType("tIME"));
+            Assert.Equal(PngChunkType.Background, GetType("bKGD"));
+            Assert.Equal(PngChunkType.EmbeddedColorProfile, GetType("iCCP"));
+            Assert.Equal(PngChunkType.StandardRgbColourSpace, GetType("sRGB"));
+            Assert.Equal(PngChunkType.SignificantBits, GetType("sBIT"));
+            Assert.Equal(PngChunkType.Histogram, GetType("hIST"));
+            Assert.Equal(PngChunkType.SuggestedPalette, GetType("sPLT"));
+            Assert.Equal(PngChunkType.MalformedApple, GetType("CgBI"));
         }
 
         private static PngChunkType GetType(string text)