How to Convert Images to Grayscale in C#?

Detailed explanation of C# image grayscale conversion

Converting images to grayscale format is a common image processing task. This article will explore how to use the System.Drawing.Imaging.PixelFormat enumeration to implement grayscale conversion in C#.

16-bit pixel grayscale format

If you need a grayscale image with 16-bit pixels, you can use the following constructor:

Bitmap grayScaleBP = new System.Drawing.Bitmap(2, 2, System.Drawing.Imaging.PixelFormat.Format16bppGrayScale);

Image grayscale conversion

To convert an existing image (c) to a grayscale image (d) you can use the following code:

Bitmap d;
int x, y;

// 循环遍历图像像素并将其颜色重置为灰度
for (x = 0; x < ...; x++) {
    for (y = 0; y < ...; y++) {
        // 灰度转换逻辑...
    }
}

(The specific grayscale conversion code in the loop body is omitted here because the original text does not provide complete loop body content)

Faster grayscale conversion method

The following is a more efficient method of image grayscale conversion:

public static Bitmap MakeGrayscale3(Bitmap original)
{
    Bitmap newBitmap = new Bitmap(original.Width, original.Height);

    using (Graphics g = Graphics.FromImage(newBitmap))
    {
        // 创建灰度ColorMatrix
        ColorMatrix colorMatrix = new ColorMatrix(
            new float[][]
            {
                new float[] {.3f, .3f, .3f, 0, 0},
                new float[] {.59f, .59f, .59f, 0, 0},
                new float[] {.11f, .11f, .11f, 0, 0},
                new float[] {0, 0, 0, 1, 0},
                new float[] {0, 0, 0, 0, 1}
            });

        // 使用灰度ColorMatrix绘制原始图像
        g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height),
                    0, 0, original.Width, original.Height, GraphicsUnit.Pixel,
                    new ImageAttributes { ColorMatrix = colorMatrix });
    }

    return newBitmap;
}

This method uses ColorMatrix to perform grayscale conversion, thus improving performance.

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