完成图片优化处理

Author: lindexi

src/MediaConverters/MediaConverters.Lib/Imaging/Optimizations/ImageFileOptimization.cs

@@ -0,0 +1,181 @@
+using System;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.Formats.Gif;
+using SixLabors.ImageSharp.Formats.Png;
+using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Processing;
+
+namespace DotNetCampus.MediaConverters.Imaging.Optimizations;
+
+public static class ImageFileOptimization
+{
+    /// <summary>
+    /// 对插入的图片进行一些预处理，以解决各种各样的图片处理问题（如 DPI 问题、内存问题、后缀名错误等）。
+    /// 其中，最大宽高是图片为 96.0 DPI 下的逻辑宽高。
+    /// 在处理完后，将返回一张新的图片路径。
+    /// </summary>
+    /// <param name="imageFile"></param>
+    /// <param name="maxImageWidth">限制图片的最大宽度。为空则表示不限制</param>
+    /// <param name="maxImageHeight">限制图片的最大高度。为空则表示不限制</param>
+    /// <param name="copyNewFile">是否先行拷贝新的文件，再进行处理，避免图片占用。默认为 true。</param>
+    /// <param name="workingFolder"></param>
+    /// <returns></returns>
+    public static async Task<ImageFileOptimizationResult> OptimizeImageFileAsync(FileInfo imageFile,
+        DirectoryInfo workingFolder, int? maxImageWidth = null, int? maxImageHeight = null, bool copyNewFile = true)
+    {
+        if (!File.Exists(imageFile.FullName))
+        {
+            // 不能依靠 imageFile.Exists 属性，因为属性可能还没更新
+            return new ImageFileOptimizationResult
+            {
+                OptimizedImageFile = null,
+                FailureReason = ImageFileOptimizationFailureReason.FileNotFound
+            };
+        }
+
+        Directory.CreateDirectory(workingFolder.FullName);
+
+        var file = imageFile;
+        if (copyNewFile)
+        {
+            var newFilePath = Path.Join(workingFolder.FullName, $"{Path.GetRandomFileName()}_{imageFile.Name}");
+            file.CopyTo(newFilePath);
+            file = new FileInfo(newFilePath);
+        }
+
+        Image<Rgba32> image;
+        try
+        {
+            await using var fileStream = new FileStream(file.FullName, FileMode.Open, FileAccess.Read, FileShare.Read);
+
+            // 额外输出旋转图片的情况
+            image = await Image.LoadAsync<Rgba32>(fileStream);
+        }
+        catch (ImageFormatException e)
+        {
+            // 这里是明确的图片处理的错误，可以转换为输出信息。如果是其他错误，继续抛出
+            ImageFileOptimizationFailureReason failureReason = default;
+
+            if (e is UnknownImageFormatException)
+            {
+                failureReason = ImageFileOptimizationFailureReason.UnknownImageFormat;
+            }
+            else if (e is InvalidImageContentException)
+            {
+                failureReason = ImageFileOptimizationFailureReason.InvalidImageContent;
+            }
+
+            return new ImageFileOptimizationResult()
+            {
+                OptimizedImageFile = null,
+                Exception = e,
+                FailureReason = failureReason
+            };
+        }
+
+        if (image.Metadata.DecodedImageFormat is GifFormat)
+        {
+            return new ImageFileOptimizationResult()
+            {
+                OptimizedImageFile = null,
+                FailureReason = ImageFileOptimizationFailureReason.NotSupported
+            };
+        }
+
+        var fileExtension = image.Metadata.DecodedImageFormat?.FileExtensions.FirstOrDefault();
+
+        if (maxImageWidth is not null && maxImageHeight is not null)
+        {
+            LimitImageSize(image, maxImageWidth.Value * maxImageHeight.Value);
+        }
+        else
+        {
+            LimitImageSize(image, maxImageWidth, maxImageHeight);
+        }
+
+        // 重新保存即可
+        var outputImageFilePath = Path.Join(workingFolder.FullName, $"{Path.GetRandomFileName()}.png");
+        await image.SaveAsPngAsync(outputImageFilePath, new PngEncoder()
+        {
+            ColorType = PngColorType.RgbWithAlpha,
+            BitDepth = PngBitDepth.Bit8,
+        });
+
+        return new ImageFileOptimizationResult()
+        {
+            OptimizedImageFile = new FileInfo(outputImageFilePath),
+            FailureReason = ImageFileOptimizationFailureReason.Ok
+        };
+    }
+
+    /// <summary>
+    /// 限制图片尺寸。按照面积方式限制，保持比例
+    /// </summary>
+    /// <param name="image"></param>
+    /// <param name="maxPixelCount"></param>
+    public static void LimitImageSize(Image<Rgba32> image, int maxPixelCount)
+    {
+        if (image.Width * image.Height <= maxPixelCount)
+        {
+            // 尺寸没有超过限制，直接返回
+            return;
+        }
+
+        var pixelWidth = (int) Math.Sqrt(maxPixelCount * image.Width / (double) image.Height);
+        var pixelHeight = (int) Math.Sqrt(maxPixelCount * image.Height / (double) image.Width);
+        image.Mutate(context => context.Resize(new Size(pixelWidth, pixelHeight), compand: true));
+    }
+
+    /// <summary>
+    /// 限制图片尺寸。保持比例
+    /// </summary>
+    /// <param name="image"></param>
+    /// <param name="maxImageWidth"></param>
+    /// <param name="maxImageHeight"></param>
+    public static void LimitImageSize(Image<Rgba32> image, int? maxImageWidth, int? maxImageHeight)
+    {
+        if (maxImageWidth is null && maxImageHeight is null)
+        {
+            return;
+        }
+
+        if (image.Width <= maxImageWidth && image.Height <= maxImageHeight)
+        {
+            return;
+        }
+
+        var pixelWidth = image.Width;
+        var pixelHeight = image.Height;
+
+        var scale = pixelWidth / (double) pixelHeight;
+
+        // 如果图片的宽度超过限制，则缩放到限制的宽度
+        if (maxImageWidth is not null && pixelWidth > maxImageWidth)
+        {
+            pixelWidth = maxImageWidth.Value;
+            pixelHeight = (int) Math.Round(pixelWidth / scale, MidpointRounding.AwayFromZero);
+        }
+
+        if (maxImageHeight is not null && pixelHeight > maxImageHeight)
+        {
+            pixelHeight = maxImageHeight.Value;
+            pixelWidth = (int) Math.Round(pixelHeight * scale, MidpointRounding.AwayFromZero);
+        }
+
+        image.Mutate(context => context.Resize(new Size(pixelWidth, pixelHeight), compand: true));
+    }
+
+    /// <summary>
+    /// 图片压缩的最大宽度
+    /// </summary>
+    private const int MaxWidth = 3840;
+
+    /// <summary>
+    /// 图片压缩的最大高度
+    /// </summary>
+    private const int MaxHeight = 2160;
+}

src/MediaConverters/MediaConverters.Lib/Imaging/Optimizations/ImageFileOptimizationFailureReason.cs

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+namespace DotNetCampus.MediaConverters.Imaging.Optimizations;
+
+public enum ImageFileOptimizationFailureReason
+{
+    /// <summary>
+    /// 没有错误
+    /// </summary>
+    Ok,
+
+    /// <summary>
+    /// 图片文件格式不支持
+    /// </summary>
+    UnknownImageFormat,
+
+    /// <summary>
+    /// 图片内容无效
+    /// </summary>
+    InvalidImageContent,
+
+    /// <summary>
+    /// 图片文件未找到
+    /// </summary>
+    FileNotFound,
+
+    /// <summary>
+    /// 不支持的图片格式
+    /// </summary>
+    NotSupported,
+}

src/MediaConverters/MediaConverters.Lib/Imaging/Optimizations/ImageFileOptimizationResult.cs

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+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
+
+namespace DotNetCampus.MediaConverters.Imaging.Optimizations;
+
+/// <summary>
+/// 图片文件优化结果
+/// </summary>
+public readonly record struct ImageFileOptimizationResult()
+{
+    /// <summary>
+    /// 优化后的图片文件
+    /// </summary>
+    public required FileInfo? OptimizedImageFile { get; init; }
+
+    public Exception? Exception { get; init; }
+    public ImageFileOptimizationFailureReason FailureReason { get; init; } = ImageFileOptimizationFailureReason.Ok;
+
+    [MemberNotNullWhen(true, nameof(OptimizedImageFile))]
+    public bool IsSuccess => OptimizedImageFile is not null;
+}