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C#實(shí)現(xiàn)將超大圖片(1GB)裁剪為8張小圖片

更新時(shí)間：2025年05月18日 10:06:32 作者：MartinYangHJ

C#處理超大圖片（1GB）需要特別注意內(nèi)存管理和性能優(yōu)化,這篇文章為大家整理了4種常見的處理方法,并進(jìn)行了對比,大家可以根據(jù)自己的需要進(jìn)行選擇

方法1：使用System.Drawing分塊處理（內(nèi)存優(yōu)化版）

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
 
class Program
{
    static void Main()
    {
        string sourceImagePath = "1GB_Image.bmp";
        string outputFolder = "CroppedImages";
        
        if (!Directory.Exists(outputFolder))
        {
            Directory.CreateDirectory(outputFolder);
        }
 
        // 獲取圖片尺寸但不加載全部內(nèi)容
        using (var image = Image.FromFile(sourceImagePath))
        {
            int totalWidth = image.Width;
            int totalHeight = image.Height;
            
            // 計(jì)算每塊尺寸 (2x4網(wǎng)格)
            int chunkWidth = totalWidth / 2;
            int chunkHeight = totalHeight / 4;
 
            // 分塊裁剪
            for (int row = 0; row < 4; row++)
            {
                for (int col = 0; col < 2; col++)
                {
                    int x = col * chunkWidth;
                    int y = row * chunkHeight;
                    
                    // 確保最后一塊包含剩余部分
                    int width = (col == 1) ? totalWidth - x : chunkWidth;
                    int height = (row == 3) ? totalHeight - y : chunkHeight;
 
                    CropImage(
                        sourceImagePath,
                        Path.Combine(outputFolder, $"part_{row}_{col}.jpg"),
                        x, y, width, height);
                }
            }
        }
    }
 
    static void CropImage(string sourcePath, string destPath, int x, int y, int width, int height)
    {
        // 使用流式處理避免全圖加載
        using (var source = new Bitmap(sourcePath))
        using (var dest = new Bitmap(width, height))
        using (var graphics = Graphics.FromImage(dest))
        {
            graphics.DrawImage(
                source,
                new Rectangle(0, 0, width, height),
                new Rectangle(x, y, width, height),
                GraphicsUnit.Pixel);
            
            // 保存為JPEG減少體積
            dest.Save(destPath, ImageFormat.Jpeg);
            Console.WriteLine($"已保存: {destPath} ({width}x{height})");
        }
    }
}

方法2：使用ImageSharp（現(xiàn)代跨平臺方案）

首先安裝NuGet包：

Install-Package SixLabors.ImageSharp

實(shí)現(xiàn)代碼：

using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Processing;
using SixLabors.ImageSharp.Formats.Jpeg;
 
class Program
{
    static async Task Main()
    {
        string sourcePath = "1GB_Image.jpg";
        string outputDir = "CroppedImages";
        
        Directory.CreateDirectory(outputDir);
 
        // 配置內(nèi)存選項(xiàng)處理大圖
        var configuration = Configuration.Default.Clone();
        configuration.MemoryAllocator = new SixLabors.ImageSharp.Memory.ArrayPoolMemoryAllocator();
 
        // 分塊加載和處理
        using (var image = await Image.LoadAsync(configuration, sourcePath))
        {
            int totalWidth = image.Width;
            int totalHeight = image.Height;
            
            int chunkWidth = totalWidth / 2;
            int chunkHeight = totalHeight / 4;
 
            for (int row = 0; row < 4; row++)
            {
                for (int col = 0; col < 2; col++)
                {
                    int x = col * chunkWidth;
                    int y = row * chunkHeight;
                    int width = (col == 1) ? totalWidth - x : chunkWidth;
                    int height = (row == 3) ? totalHeight - y : chunkHeight;
 
                    // 克隆并裁剪區(qū)域
                    using (var cropped = image.Clone(ctx => ctx
                        .Crop(new Rectangle(x, y, width, height))))
                    {
                        string outputPath = Path.Combine(outputDir, $"part_{row}_{col}.jpg");
                        await cropped.SaveAsync(outputPath, new JpegEncoder 
                        {
                            Quality = 80 // 適當(dāng)壓縮
                        });
                        Console.WriteLine($"已保存: {outputPath}");
                    }
                }
            }
        }
    }
}

方法3：使用內(nèi)存映射文件處理超大圖

using System;
using System.IO;
using System.IO.MemoryMappedFiles;
using System.Drawing;
using System.Drawing.Imaging;
 
class Program
{
    static void Main()
    {
        string sourcePath = "1GB_Image.bmp";
        string outputDir = "CroppedImages";
        
        Directory.CreateDirectory(outputDir);
 
        // 獲取BMP文件頭信息
        var bmpInfo = GetBmpInfo(sourcePath);
        int width = bmpInfo.Width;
        int height = bmpInfo.Height;
        int bytesPerPixel = bmpInfo.BitsPerPixel / 8;
        int stride = width * bytesPerPixel;
 
        // 計(jì)算分塊
        int chunkWidth = width / 2;
        int chunkHeight = height / 4;
 
        // 使用內(nèi)存映射文件處理
        using (var mmf = MemoryMappedFile.CreateFromFile(sourcePath, FileMode.Open))
        {
            for (int row = 0; row < 4; row++)
            {
                for (int col = 0; col < 2; col++)
                {
                    int x = col * chunkWidth;
                    int y = row * chunkHeight;
                    int cropWidth = (col == 1) ? width - x : chunkWidth;
                    int cropHeight = (row == 3) ? height - y : chunkHeight;
 
                    // 創(chuàng)建目標(biāo)位圖
                    using (var dest = new Bitmap(cropWidth, cropHeight, PixelFormat.Format24bppRgb))
                    {
                        var destData = dest.LockBits(
                            new Rectangle(0, 0, cropWidth, cropHeight),
                            ImageLockMode.WriteOnly,
                            dest.PixelFormat);
 
                        try
                        {
                            // 計(jì)算源文件偏移量(BMP文件頭54字節(jié) + 數(shù)據(jù)偏移)
                            long offset = 54 + (height - y - 1) * stride + x * bytesPerPixel;
                            
                            // 逐行復(fù)制
                            for (int line = 0; line < cropHeight; line++)
                            {
                                using (var accessor = mmf.CreateViewAccessor(
                                    offset - line * stride, 
                                    cropWidth * bytesPerPixel))
                                {
                                    byte[] lineData = new byte[cropWidth * bytesPerPixel];
                                    accessor.ReadArray(0, lineData, 0, lineData.Length);
                                    
                                    IntPtr destPtr = destData.Scan0 + (line * destData.Stride);
                                    System.Runtime.InteropServices.Marshal.Copy(lineData, 0, destPtr, lineData.Length);
                                }
                            }
                        }
                        finally
                        {
                            dest.UnlockBits(destData);
                        }
 
                        string outputPath = Path.Combine(outputDir, $"part_{row}_{col}.jpg");
                        dest.Save(outputPath, ImageFormat.Jpeg);
                        Console.WriteLine($"已保存: {outputPath}");
                    }
                }
            }
        }
    }
 
    static (int Width, int Height, int BitsPerPixel) GetBmpInfo(string filePath)
    {
        using (var fs = new FileStream(filePath, FileMode.Open))
        using (var reader = new BinaryReader(fs))
        {
            // 讀取BMP頭
            if (reader.ReadChar() != 'B' || reader.ReadChar() != 'M')
                throw new Exception("不是有效的BMP文件");
            
            fs.Seek(18, SeekOrigin.Begin); // 跳轉(zhuǎn)到寬度信息
            int width = reader.ReadInt32();
            int height = reader.ReadInt32();
            fs.Seek(28, SeekOrigin.Begin); // 跳轉(zhuǎn)到位深信息
            int bitsPerPixel = reader.ReadInt16();
            
            return (width, height, bitsPerPixel);
        }
    }
}

方法4：使用Magick.NET（專業(yè)圖像處理）

首先安裝NuGet包：

Install-Package Magick.NET-Q16-x64

實(shí)現(xiàn)代碼：

using ImageMagick;
using System;
using System.IO;
 
class Program
{
    static void Main()
    {
        string sourcePath = "1GB_Image.tif";
        string outputDir = "CroppedImages";
        
        Directory.CreateDirectory(outputDir);
 
        // 設(shè)置資源限制
        MagickNET.SetResourceLimit(ResourceType.Memory, 1024 * 1024 * 1024); // 1GB
 
        // 使用像素流處理大圖
        using (var image = new MagickImage(sourcePath))
        {
            int width = image.Width;
            int height = image.Height;
            
            int chunkWidth = width / 2;
            int chunkHeight = height / 4;
 
            for (int row = 0; row < 4; row++)
            {
                for (int col = 0; col < 2; col++)
                {
                    int x = col * chunkWidth;
                    int y = row * chunkHeight;
                    int cropWidth = (col == 1) ? width - x : chunkWidth;
                    int cropHeight = (row == 3) ? height - y : chunkHeight;
 
                    using (var cropped = image.Clone(new MagickGeometry
                    {
                        X = x,
                        Y = y,
                        Width = cropWidth,
                        Height = cropHeight
                    }))
                    {
                        string outputPath = Path.Combine(outputDir, $"part_{row}_{col}.jpg");
                        cropped.Quality = 85;
                        cropped.Write(outputPath);
                        Console.WriteLine($"已保存: {outputPath}");
                    }
                }
            }
        }
    }
}

裁剪方案選擇建議

方法	優(yōu)點(diǎn)	缺點(diǎn)	使用場景
System.Drawing	內(nèi)置庫，簡單	內(nèi)存占用高	Windows小圖處理
ImageSharp	跨平臺，現(xiàn)代API	學(xué)習(xí)曲線	需要跨平臺支持
內(nèi)存映射	內(nèi)存效率高	復(fù)雜，僅限BMP	超大圖處理
Magick.NET	功能強(qiáng)大	需要安裝	專業(yè)圖像處理