From ec3656ff7a189acc6adf3d2f7df04aef22d5f4ef Mon Sep 17 00:00:00 2001 From: Brian Popow Date: Fri, 1 May 2020 10:38:47 +0200 Subject: [PATCH] Add PngTransparentColorBehavior enum --- .../Formats/Png/IPngEncoderOptions.cs | 5 +++-- src/ImageSharp/Formats/Png/PngEncoder.cs | 2 +- src/ImageSharp/Formats/Png/PngEncoderCore.cs | 15 +++++++------ .../Formats/Png/PngEncoderOptions.cs | 4 ++-- .../Png/PngTransparentColorBehavior.cs | 22 +++++++++++++++++++ .../Formats/Png/PngEncoderTests.cs | 8 +++---- 6 files changed, 39 insertions(+), 17 deletions(-) create mode 100644 src/ImageSharp/Formats/Png/PngTransparentColorBehavior.cs diff --git a/src/ImageSharp/Formats/Png/IPngEncoderOptions.cs b/src/ImageSharp/Formats/Png/IPngEncoderOptions.cs index 770afa3c5..ca9d5757f 100644 --- a/src/ImageSharp/Formats/Png/IPngEncoderOptions.cs +++ b/src/ImageSharp/Formats/Png/IPngEncoderOptions.cs @@ -70,8 +70,9 @@ namespace SixLabors.ImageSharp.Formats.Png PngChunkFilter? ChunkFilter { get; } /// - /// Gets a value indicating whether fully transparent pixels should be converted to black pixels. + /// Gets a value indicating whether fully transparent pixels that may contain R, G, B values which are not 0, + /// should be converted to transparent black, which can yield in better compression in some cases. /// - bool MakeTransparentBlack { get; } + PngTransparentColorBehavior TransparentColorBehavior { get; } } } diff --git a/src/ImageSharp/Formats/Png/PngEncoder.cs b/src/ImageSharp/Formats/Png/PngEncoder.cs index 062e56c1d..d4ca4b7df 100644 --- a/src/ImageSharp/Formats/Png/PngEncoder.cs +++ b/src/ImageSharp/Formats/Png/PngEncoder.cs @@ -47,7 +47,7 @@ namespace SixLabors.ImageSharp.Formats.Png public bool IgnoreMetadata { get; set; } /// - public bool MakeTransparentBlack { get; set; } + public PngTransparentColorBehavior TransparentColorBehavior { get; set; } /// /// Encodes the image to the specified stream from the . diff --git a/src/ImageSharp/Formats/Png/PngEncoderCore.cs b/src/ImageSharp/Formats/Png/PngEncoderCore.cs index 12ffb2cfc..05c17f376 100644 --- a/src/ImageSharp/Formats/Png/PngEncoderCore.cs +++ b/src/ImageSharp/Formats/Png/PngEncoderCore.cs @@ -145,10 +145,11 @@ namespace SixLabors.ImageSharp.Formats.Png PngMetadata pngMetadata = metadata.GetFormatMetadata(PngFormat.Instance); PngEncoderOptionsHelpers.AdjustOptions(this.options, pngMetadata, out this.use16Bit, out this.bytesPerPixel); Image clonedImage = null; - if (this.options.MakeTransparentBlack) + bool clearTransparency = this.options.TransparentColorBehavior == PngTransparentColorBehavior.Clear; + if (clearTransparency) { clonedImage = image.Clone(); - MakeTransparentPixelsBlack(clonedImage); + ClearTransparentPixels(clonedImage); } IndexedImageFrame quantized = this.CreateQuantizedImage(image, clonedImage); @@ -162,7 +163,7 @@ namespace SixLabors.ImageSharp.Formats.Png this.WritePhysicalChunk(stream, metadata); this.WriteExifChunk(stream, metadata); this.WriteTextChunks(stream, pngMetadata); - this.WriteDataChunks(this.options.MakeTransparentBlack ? clonedImage : image, quantized, stream); + this.WriteDataChunks(clearTransparency ? clonedImage : image, quantized, stream); this.WriteEndChunk(stream); stream.Flush(); @@ -190,11 +191,11 @@ namespace SixLabors.ImageSharp.Formats.Png } /// - /// Makes transparent pixels black. + /// Convert transparent pixels, to transparent black pixels, which can yield to better compression in some cases. /// /// The type of the pixel. /// The cloned image where the transparent pixels will be changed. - private static void MakeTransparentPixelsBlack(Image image) + private static void ClearTransparentPixels(Image image) where TPixel : unmanaged, IPixel { Rgba32 rgba32 = default; @@ -207,7 +208,7 @@ namespace SixLabors.ImageSharp.Formats.Png if (rgba32.A == 0) { - span[x].FromRgba32(Color.Black); + span[x].FromRgba32(Color.Transparent); } } } @@ -224,7 +225,7 @@ namespace SixLabors.ImageSharp.Formats.Png where TPixel : unmanaged, IPixel { IndexedImageFrame quantized; - if (this.options.MakeTransparentBlack) + if (this.options.TransparentColorBehavior == PngTransparentColorBehavior.Clear) { quantized = PngEncoderOptionsHelpers.CreateQuantizedFrame(this.options, clonedImage); this.bitDepth = PngEncoderOptionsHelpers.CalculateBitDepth(this.options, quantized); diff --git a/src/ImageSharp/Formats/Png/PngEncoderOptions.cs b/src/ImageSharp/Formats/Png/PngEncoderOptions.cs index d0eb1a843..e46dafada 100644 --- a/src/ImageSharp/Formats/Png/PngEncoderOptions.cs +++ b/src/ImageSharp/Formats/Png/PngEncoderOptions.cs @@ -31,7 +31,7 @@ namespace SixLabors.ImageSharp.Formats.Png this.InterlaceMethod = source.InterlaceMethod; this.ChunkFilter = source.ChunkFilter; this.IgnoreMetadata = source.IgnoreMetadata; - this.MakeTransparentBlack = source.MakeTransparentBlack; + this.TransparentColorBehavior = source.TransparentColorBehavior; } /// @@ -68,6 +68,6 @@ namespace SixLabors.ImageSharp.Formats.Png public bool IgnoreMetadata { get; set; } /// - public bool MakeTransparentBlack { get; set; } + public PngTransparentColorBehavior TransparentColorBehavior { get; set; } } } diff --git a/src/ImageSharp/Formats/Png/PngTransparentColorBehavior.cs b/src/ImageSharp/Formats/Png/PngTransparentColorBehavior.cs new file mode 100644 index 000000000..b459751c4 --- /dev/null +++ b/src/ImageSharp/Formats/Png/PngTransparentColorBehavior.cs @@ -0,0 +1,22 @@ +// Copyright (c) Six Labors and contributors. +// Licensed under the GNU Affero General Public License, Version 3. + +namespace SixLabors.ImageSharp.Formats.Png +{ + /// + /// Enum indicating how the transparency should be handled on encoding. + /// + public enum PngTransparentColorBehavior + { + /// + /// Converts fully transparent pixels that may contain R, G, B values which are not 0, + /// to transparent black, which can yield in better compression in some cases. + /// + Clear, + + /// + /// The transparency will be kept as is. + /// + Preserve + } +} diff --git a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs index 857445260..d29279b29 100644 --- a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs +++ b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs @@ -392,17 +392,15 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png [Theory] [InlineData(PngColorType.Palette)] - [InlineData(PngColorType.Rgb)] [InlineData(PngColorType.RgbWithAlpha)] - [InlineData(PngColorType.Grayscale)] [InlineData(PngColorType.GrayscaleWithAlpha)] - public void Encode_WithMakeTransparentBlackOption_Works(PngColorType colorType) + public void Encode_WithPngTransparentColorBehaviorClear_Works(PngColorType colorType) { // arrange var image = new Image(50, 50); var encoder = new PngEncoder() { - MakeTransparentBlack = true, + TransparentColorBehavior = PngTransparentColorBehavior.Clear, ColorType = colorType }; Rgba32 rgba32 = Color.Blue; @@ -442,7 +440,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png if (y > 25) { - expectedColor = Color.Black; + expectedColor = Color.Transparent; } for (int x = 0; x < actual.Width; x++)