C# 如何将32位深的bmp转成24位深的BMP

以下 C# 将32位深的 BMP 转成 24位深的 BMP 的示例代码：

using System.Drawing;
using System.Drawing.Imaging;

public static void Convert32BitTo24Bit(string inputFilePath, string outputFilePath)
{
    // Load the input bitmap.
    Bitmap inputBitmap = new Bitmap(inputFilePath);

    // Create a new 24-bit bitmap with the same dimensions as the input bitmap.
    Bitmap outputBitmap = new Bitmap(inputBitmap.Width, inputBitmap.Height, PixelFormat.Format24bppRgb);

    // Lock the input bitmap's bits.
    Rectangle inputRect = new Rectangle(0, 0, inputBitmap.Width, inputBitmap.Height);
    BitmapData inputData = inputBitmap.LockBits(inputRect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

    // Lock the output bitmap's bits.
    Rectangle outputRect = new Rectangle(0, 0, outputBitmap.Width, outputBitmap.Height);
    BitmapData outputData = outputBitmap.LockBits(outputRect, ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);

    // Copy the input bitmap's bits to the output bitmap, discarding the alpha channel.
    unsafe
    {
        byte* inputPtr = (byte*)inputData.Scan0;
        byte* outputPtr = (byte*)outputData.Scan0;

        for (int y = 0; y < inputBitmap.Height; y++)
        {
            for (int x = 0; x < inputBitmap.Width; x++)
            {
                outputPtr[0] = inputPtr[2];
                outputPtr[1] = inputPtr[1];
                outputPtr[2] = inputPtr[0];

                inputPtr += 4;
                outputPtr += 3;
            }

            inputPtr += inputData.Stride - (inputBitmap.Width * 4);
            outputPtr += outputData.Stride - (inputBitmap.Width * 3);
        }
    }

    // Unlock the input bitmap's bits.
    inputBitmap.UnlockBits(inputData);

    // Unlock the output bitmap's bits.
    outputBitmap.UnlockBits(outputData);

    // Save the output bitmap.
    outputBitmap.Save(outputFilePath, ImageFormat.Bmp);
}

使用示例：

Convert32BitTo24Bit("input.bmp", "output.bmp");

其中，`inputFilePath` 参数是要转换的 BMP 文件路径，`outputFilePath` 参数是转换后的 BMP 文件路径。