C# 调整图像的亮度对比度和伽玛值
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Adjust brightness contrast and gamma of an image
提问by VladL
What is an easy way to adjust brightness contrast and gamma of an Image in .NET
在 .NET 中调整图像亮度对比度和伽玛的简单方法是什么
Will post the answer myself to find it later.
将自己发布答案以供稍后查找。
采纳答案by VladL
c# and gdi+ have a simple way to control the colors that are drawn. It's basically a ColorMatrix. It's a 5×5 matrix that is applied to each color if it is set. Adjusting brightness is just performing a translate on the color data, and contrast is performing a scale on the color. Gamma is a whole different form of transform, but it's included in ImageAttributes which accepts the ColorMatrix.
c# 和 gdi+ 有一种简单的方法来控制绘制的颜色。它基本上是一个 ColorMatrix。它是一个 5×5 的矩阵，如果它被设置，则应用于每种颜色。调整亮度只是对颜色数据进行转换，而对比度则是对颜色进行缩放。Gamma 是一种完全不同的变换形式，但它包含在接受 ColorMatrix 的 ImageAttributes 中。
Bitmap originalImage;
Bitmap adjustedImage;
float brightness = 1.0f; // no change in brightness
float contrast = 2.0f; // twice the contrast
float gamma = 1.0f; // no change in gamma
float adjustedBrightness = brightness - 1.0f;
// create matrix that will brighten and contrast the image
float[][] ptsArray ={
new float[] {contrast, 0, 0, 0, 0}, // scale red
new float[] {0, contrast, 0, 0, 0}, // scale green
new float[] {0, 0, contrast, 0, 0}, // scale blue
new float[] {0, 0, 0, 1.0f, 0}, // don't scale alpha
new float[] {adjustedBrightness, adjustedBrightness, adjustedBrightness, 0, 1}};
ImageAttributes imageAttributes = new ImageAttributes();
imageAttributes.ClearColorMatrix();
imageAttributes.SetColorMatrix(new ColorMatrix(ptsArray), ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
imageAttributes.SetGamma(gamma, ColorAdjustType.Bitmap);
Graphics g = Graphics.FromImage(adjustedImage);
g.DrawImage(originalImage, new Rectangle(0,0,adjustedImage.Width,adjustedImage.Height)
,0,0,originalImage.Width,originalImage.Height,
GraphicsUnit.Pixel, imageAttributes);
