C#如何增加图片的色调？

Question

我有一张图片，里面有文字。我已经使用 ColorMatrix 将该图片转换为灰度。

public Bitmap MakeGrayscale(Bitmap original)
{
    //create a blank bitmap the same size as original
    Bitmap newBitmap = new Bitmap(original.Width, original.Height);

    //get a graphics object from the new image
    Graphics g = Graphics.FromImage(newBitmap);

    //create the grayscale ColorMatrix
    ColorMatrix colorMatrix = new ColorMatrix(
       new float[][] 
         {
     new float[] {.3f, .3f, .3f, 0, 0}, // 30% red.
     new float[] {.59f, .59f, .59f, 0, 0}, // 59% green.
     new float[] {.11f, .11f, .11f, 0, 0}, // 11% blue.
     new float[] {0, 0, 0, 1, 0},
     new float[] {0, 0, 0, 0, 1}
          });

    //create some image attributes
    ImageAttributes attributes = new ImageAttributes();


    //set the color matrix attribute
    attributes.SetColorMatrix(colorMatrix);

    //draw the original image on the new image
    //using the grayscale color matrix
    g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height),
       0, 0, original.Width, original.Height, GraphicsUnit.Pixel, attributes);

    //dispose the Graphics object
    g.Dispose();
    return newBitmap;
}

现在，这是相当灰度的（黑白色调）。我想增加黑色调并使其变暗，这可以用 Photoshop 来实现。请告诉我如何在 C# 中实现这一目标？

请告诉我。

干杯! :)

Answer 1

一种方法是通常强制像素变暗，尝试迭代位图中的所有像素（颜色对象），并将它们替换为按百分比变暗的新颜色
这段代码可能会有所帮助

    /// <summary>
    /// Darkens the immage, giving a number greater then one will not brighten the image correctly
    /// </summary>
    /// <param name="bmp">The bitmap to darken</param>
    /// <param name="multiplier">The multiplier, should be less then oen to darker the picture</param>
    static void DarkenImage(Bitmap bmp, double multiplier)
    {
        for (int i = 0; i < bmp.Width; i++)
        {
            // Iterates over all the pixels
            for (int j = 0; j < bmp.Height; j++)
            {
                // Gets the current pixel
                var currentPixel = bmp.GetPixel(i, j);

                // Assigns each value the multiply, or the max value 255
                var newPixel = Color.FromArgb(
                    Math.Min((byte)255, (byte)(currentPixel.R * multiplier)),
                    Math.Min((byte)255, (byte)(currentPixel.G * multiplier)),
                    Math.Min((byte)255, (byte)(currentPixel.B * multiplier))
                    );

                // Sets the pixel 
                bmp.SetPixel(i, j, newPixel);
            }
        }
    }