亮度和对比度应该是最常见的处理要求了。就算是N年前9寸黑白电视机也必有这两个旋钮。
亮度调整算法很简单。对每一个像素的RGB值同时加上或减去一个特定的值就可以了。当然由于RGB取值范围都是在[0,255]的,所以要考虑到越界的问题。
/**//// <summary>
/// 图像明暗调整
/// </summary>
/// <param name="b">原始图</param>
/// <param name="degree">亮度[-255, 255]</param>
/// <returns></returns>
public static Bitmap KiLighten(Bitmap b, int degree)
...{
if (b == null)
...{
return null;
}
if (degree < -255) degree = -255;
if (degree > 255) degree = 255;
try
...{
int width = b.Width;
int height = b.Height;
int pix = 0;
BitmapData data = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
unsafe
...{
byte* p = (byte*)data.Scan0;
int offset = data.Stride - width * 3;
for (int y = 0; y < height; y++)
...{
for (int x = 0; x < width; x++)
...{
// 处理指定位置像素的亮度
for (int i = 0; i < 3; i++)
...{
pix = p[i] + degree;
if (degree < 0) p[i] = (byte)Math.Max(0, pix);
if (degree > 0) p[i] = (byte)Math.Min(255, pix);
} // i
p += 3;
} // x
p += offset;
} // y
}
b.UnlockBits(data);
return b;
}
catch
...{
return null;
}
} // end of Lighten
/// 图像明暗调整
/// </summary>
/// <param name="b">原始图</param>
/// <param name="degree">亮度[-255, 255]</param>
/// <returns></returns>
public static Bitmap KiLighten(Bitmap b, int degree)
...{
if (b == null)
...{
return null;
}
if (degree < -255) degree = -255;
if (degree > 255) degree = 255;
try
...{
int width = b.Width;
int height = b.Height;
int pix = 0;
BitmapData data = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
unsafe
...{
byte* p = (byte*)data.Scan0;
int offset = data.Stride - width * 3;
for (int y = 0; y < height; y++)
...{
for (int x = 0; x < width; x++)
...{
// 处理指定位置像素的亮度
for (int i = 0; i < 3; i++)
...{
pix = p[i] + degree;
if (degree < 0) p[i] = (byte)Math.Max(0, pix);
if (degree > 0) p[i] = (byte)Math.Min(255, pix);
} // i
p += 3;
} // x
p += offset;
} // y
}
b.UnlockBits(data);
return b;
}
catch
...{
return null;
}
} // end of Lighten
对比度校正的思想也很简单,大的原则就是让亮的更亮,暗的更暗。具体实现的方式有很多种,比如取一个阀值,超过的就加一定的值,不到的就减一定的值等等。
/**//// <summary>
/// 图像对比度调整
/// </summary>
/// <param name="b">原始图</param>
/// <param name="degree">对比度[-100, 100]</param>
/// <returns></returns>
public static Bitmap KiContrast(Bitmap b, int degree)
...{
if (b == null)
...{
return null;
}
if (degree < -100) degree = -100;
if (degree > 100) degree = 100;
try
...{
double pixel = 0;
double contrast = (100.0 + degree) / 100.0;
contrast *= contrast;
int width = b.Width;
int height = b.Height;
BitmapData data = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
unsafe
...{
byte* p = (byte*)data.Scan0;
int offset = data.Stride - width * 3;
for (int y = 0; y < height; y++)
...{
for (int x = 0; x < width; x++)
...{
// 处理指定位置像素的对比度
for (int i = 0; i < 3; i++)
...{
pixel = ((p[i] / 255.0 - 0.5) * contrast + 0.5) * 255;
if (pixel < 0) pixel = 0;
if (pixel > 255) pixel = 255;
p[i] = (byte)pixel;
} // i
p += 3;
} // x
p += offset;
} // y
}
b.UnlockBits(data);
return b;
}
catch
...{
return null;
}
} // end of Contrast
/// 图像对比度调整
/// </summary>
/// <param name="b">原始图</param>
/// <param name="degree">对比度[-100, 100]</param>
/// <returns></returns>
public static Bitmap KiContrast(Bitmap b, int degree)
...{
if (b == null)
...{
return null;
}
if (degree < -100) degree = -100;
if (degree > 100) degree = 100;
try
...{
double pixel = 0;
double contrast = (100.0 + degree) / 100.0;
contrast *= contrast;
int width = b.Width;
int height = b.Height;
BitmapData data = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
unsafe
...{
byte* p = (byte*)data.Scan0;
int offset = data.Stride - width * 3;
for (int y = 0; y < height; y++)
...{
for (int x = 0; x < width; x++)
...{
// 处理指定位置像素的对比度
for (int i = 0; i < 3; i++)
...{
pixel = ((p[i] / 255.0 - 0.5) * contrast + 0.5) * 255;
if (pixel < 0) pixel = 0;
if (pixel > 255) pixel = 255;
p[i] = (byte)pixel;
} // i
p += 3;
} // x
p += offset;
} // y
}
b.UnlockBits(data);
return b;
}
catch
...{
return null;
}
} // end of Contrast