mirror of https://github.com/SixLabors/ImageSharp
James Jackson-South
7 years ago
committed by
GitHub
GitHub
7 changed files with 223 additions and 181 deletions
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// Copyright (c) Six Labors and contributors.
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// Licensed under the Apache License, Version 2.0.
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#if !NETCOREAPP2_1
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using System; |
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using System.Text; |
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namespace SixLabors.ImageSharp |
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{ |
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/// <summary>
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/// Extension methods for the <see cref="Encoder"/> type.
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/// </summary>
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internal static unsafe class EncoderExtensions |
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{ |
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/// <summary>
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/// Gets a string from the provided buffer data.
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/// </summary>
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/// <param name="encoding">The encoding.</param>
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/// <param name="buffer">The buffer.</param>
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/// <returns>The string.</returns>
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public static string GetString(this Encoding encoding, ReadOnlySpan<byte> buffer) |
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{ |
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#if NETSTANDARD1_1
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return encoding.GetString(buffer.ToArray()); |
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#else
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fixed (byte* bytes = buffer) |
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{ |
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return encoding.GetString(bytes, buffer.Length); |
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} |
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#endif
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} |
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} |
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} |
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#endif
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@ -0,0 +1,107 @@ |
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using System; |
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using System.Buffers.Binary; |
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using SixLabors.ImageSharp.Common.Helpers; |
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using SixLabors.ImageSharp.MetaData; |
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namespace SixLabors.ImageSharp.Formats.Png.Chunks |
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{ |
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/// <summary>
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/// The pHYs chunk specifies the intended pixel size or aspect ratio for display of the image.
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/// </summary>
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internal readonly struct PhysicalChunkData |
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{ |
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public const int Size = 9; |
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public PhysicalChunkData(uint x, uint y, byte unitSpecifier) |
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{ |
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this.XAxisPixelsPerUnit = x; |
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this.YAxisPixelsPerUnit = y; |
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this.UnitSpecifier = unitSpecifier; |
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} |
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/// <summary>
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/// Gets the number of pixels per unit on the X axis.
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/// </summary>
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public uint XAxisPixelsPerUnit { get; } |
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/// <summary>
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/// Gets the number of pixels per unit on the Y axis.
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/// </summary>
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public uint YAxisPixelsPerUnit { get; } |
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/// <summary>
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/// Gets the unit specifier.
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/// 0: unit is unknown
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/// 1: unit is the meter
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/// When the unit specifier is 0, the pHYs chunk defines pixel aspect ratio only; the actual size of the pixels remains unspecified.
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/// </summary>
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public byte UnitSpecifier { get; } |
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/// <summary>
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/// Parses the PhysicalChunkData from the given buffer.
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/// </summary>
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/// <param name="data">The data buffer.</param>
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/// <returns>The parsed PhysicalChunkData.</returns>
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public static PhysicalChunkData Parse(ReadOnlySpan<byte> data) |
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{ |
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uint hResolution = BinaryPrimitives.ReadUInt32BigEndian(data.Slice(0, 4)); |
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uint vResolution = BinaryPrimitives.ReadUInt32BigEndian(data.Slice(4, 4)); |
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byte unit = data[8]; |
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return new PhysicalChunkData(hResolution, vResolution, unit); |
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} |
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/// <summary>
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/// Constructs the PngPhysicalChunkData from the provided metadata.
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/// If the resolution units are not in meters, they are automatically convereted.
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/// </summary>
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/// <param name="meta">The metadata.</param>
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/// <returns>The constructed PngPhysicalChunkData instance.</returns>
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public static PhysicalChunkData FromMetadata(ImageMetaData meta) |
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{ |
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byte unitSpecifier = 0; |
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uint x; |
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uint y; |
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switch (meta.ResolutionUnits) |
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{ |
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case PixelResolutionUnit.AspectRatio: |
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unitSpecifier = 0; // Unspecified
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x = (uint)Math.Round(meta.HorizontalResolution); |
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y = (uint)Math.Round(meta.VerticalResolution); |
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break; |
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case PixelResolutionUnit.PixelsPerInch: |
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unitSpecifier = 1; // Per meter
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x = (uint)Math.Round(UnitConverter.InchToMeter(meta.HorizontalResolution)); |
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y = (uint)Math.Round(UnitConverter.InchToMeter(meta.VerticalResolution)); |
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break; |
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case PixelResolutionUnit.PixelsPerCentimeter: |
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unitSpecifier = 1; // Per meter
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x = (uint)Math.Round(UnitConverter.CmToMeter(meta.HorizontalResolution)); |
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y = (uint)Math.Round(UnitConverter.CmToMeter(meta.VerticalResolution)); |
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break; |
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default: |
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unitSpecifier = 1; // Per meter
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x = (uint)Math.Round(meta.HorizontalResolution); |
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y = (uint)Math.Round(meta.VerticalResolution); |
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break; |
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} |
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return new PhysicalChunkData(x, y, unitSpecifier); |
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} |
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/// <summary>
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/// Writes the data to the given buffer.
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/// </summary>
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/// <param name="buffer">The buffer.</param>
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public void WriteTo(Span<byte> buffer) |
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{ |
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BinaryPrimitives.WriteUInt32BigEndian(buffer.Slice(0, 4), this.XAxisPixelsPerUnit); |
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BinaryPrimitives.WriteUInt32BigEndian(buffer.Slice(4, 4), this.YAxisPixelsPerUnit); |
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buffer[8] = this.UnitSpecifier; |
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} |
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} |
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} |
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