How Can I Optimize Bitmap Manipulation in C# for Better Performance?

Tips to improve C# bitmap processing performance

Directly accessing and modifying bitmap pixels is a computationally intensive operation, especially when using the standard Bitmap.GetPixel() and Bitmap.SetPixel() methods. To improve performance, consider the following techniques:

Convert bitmap to byte array and back

For fast batch operations on bitmap pixels, you can convert the bitmap to a byte array and process the raw pixel data directly. This can significantly reduce runtime by avoiding the overhead of individual pixel accesses.

The following code demonstrates how to convert a bitmap to a byte array:

<code class="language-csharp">public static byte[] BitmapToByteArray(Bitmap bitmap)
{
    int size = bitmap.Width * bitmap.Height * 4; // 假设为32位RGBA格式
    byte[] data = new byte[size];

    BitmapData bData = bitmap.LockBits(
        new Rectangle(0, 0, bitmap.Width, bitmap.Height),
        ImageLockMode.ReadOnly,
        PixelFormat.Format32bppArgb);

    Marshal.Copy(bData.Scan0, data, 0, size);

    return data;
}</code>

The following code demonstrates how to convert a byte array back to a bitmap:

<code class="language-csharp">public static Bitmap ByteArrayToBitmap(byte[] data, int width, int height)
{
    int size = width * height * 4; // 假设为32位RGBA格式
    Bitmap bitmap = new Bitmap(width, height, PixelFormat.Format32bppArgb);

    BitmapData bData = bitmap.LockBits(
        new Rectangle(0, 0, width, height),
        ImageLockMode.WriteOnly,
        PixelFormat.Format32bppArgb);

    Marshal.Copy(data, 0, bData.Scan0, size);

    return bitmap;
}</code>

Use insecure code to directly access pixel data

For best performance, you can use unsafe code to access bitmap pixel data directly. This avoids the overhead of marshaling and provides the fastest possible access speed.

The following code shows an example of using unsafe code to modify bitmap pixels:

<code class="language-csharp">public unsafe void ModifyPixelsUnsafe(Bitmap bitmap)
{
    BitmapData bData = bitmap.LockBits(
        new Rectangle(0, 0, bitmap.Width, bitmap.Height),
        ImageLockMode.ReadWrite,
        PixelFormat.Format32bppArgb);

    byte* scan0 = (byte*)bData.Scan0.ToPointer();
    // ... 直接操作 scan0 指针访问像素数据 ...
}</code>

Please note that unsafe code should be used with caution as it may cause memory corruption if used incorrectly.

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