C# 压缩图片

.net下跨平台图像处理

https://github.com/mono/SkiaSharp

安装包

skiasharp

效果

代码

ImageCompression.cs

using SkiaSharp;namespace ImageCompressStu01
{/// <summary>/// 图片压缩/// </summary>public class ImageCompression{/// <summary>/// 压缩图片/// </summary>/// <param name="source">原文件位置</param>/// <param name="target">生成目标文件位置</param>/// <param name="maxWidth">最大宽度，根据此宽度计算是否需要缩放，计算新高度</param>/// <param name="quality">图片质量，范围0-100</param>public static void Compress(string source, string target, decimal maxWidth, int quality){using (var file = File.OpenRead(source))using (var fileStream = new SKManagedStream(file))using (var bitmap = SKBitmap.Decode(fileStream)){var width = (decimal)bitmap.Width;var height = (decimal)bitmap.Height;var newWidth = width;var newHeight = height;if (width > maxWidth){newWidth = maxWidth;newHeight = height / width * maxWidth;}using (var resized = bitmap.Resize(new SKImageInfo((int)newWidth, (int)newHeight), SKFilterQuality.Medium)){if (resized != null){using (var image = SKImage.FromBitmap(resized))using (var writeStream = File.OpenWrite(target)){image.Encode(SKEncodedImageFormat.Jpeg, quality).SaveTo(writeStream);}}}}}}
}

Program.cs

namespace ImageCompressStu01
{internal class Program{static void Main(string[] args){string source = "001.jpg";//实验1 不改变尺寸，图片质量改为80，存为jpg图片ImageCompression.Compress(source, "target-1.jpg", 1920, 80);//实验2 不改变尺寸，图片质量改为80，存为png图片ImageCompression.Compress(source, "target-2.png", 1920, 80);//实验3 尺寸缩放到宽度800，图片质量改为80，存为jpg图片ImageCompression.Compress(source, "target-3.jpg", 800, 80);//实验4 尺寸缩放到宽度800，图片质量改为60，存为jpg图片ImageCompression.Compress(source, "target-4.jpg", 800, 60);}}
}

这个是针对桌面或者控制台项目，web项目处理方式可以参考下面的方法

/// <summary>
/// 压缩图片
/// </summary>
/// <param name="file">IFormFile转化为stream</param>
/// <param name="maxWidth">最大宽度，根据此宽度计算是否需要缩放，计算新高度</param>
/// <param name="quality">图片质量，范围0-100</param>
public static byte[]? Compress(Stream file, decimal maxWidth, int quality)
{byte[]? result = null;using (var fileStream = new SKManagedStream(file))using (var bitmap = SKBitmap.Decode(fileStream)){var width = (decimal)bitmap.Width;var height = (decimal)bitmap.Height;var newWidth = width;var newHeight = height;if (width > maxWidth){newWidth = maxWidth;newHeight = height / width * maxWidth;}using (var resized = bitmap.Resize(new SKImageInfo((int)newWidth, (int)newHeight), SKFilterQuality.Medium)){if (resized != null){using (var image = SKImage.FromBitmap(resized)){result = image.Encode(SKEncodedImageFormat.Jpeg, quality).ToArray();}}}}return result;
}

IFormfile转stream方法如下

//内存流
var memory = new MemoryStream();
await formFile.CopyToAsync(memory);
//一定要重置一下，要不然执行压缩会报错
stream.Seek(0, SeekOrigin.Begin);
//文件流
var filePath = "xxxxx.txt";
using (var stream = System.IO.File.Create(filePath))
{await formFile.CopyToAsync(stream);
}

参考1
参考2

扩展

生成海报的开源库，可以跨平台使用
https://github.com/SixLabors/ImageSharp