锐化
在图像处理中需要有边缘鲜明的图像，即需对图像进行锐化。因为锐化能够突出图像的边缘信息。加强图像的轮廓特征，使之便于人眼的观察或机器的识别。另外，从处理效果来看，锐化是一种与滤波相反的图像处理技术。
常用的锐化算法有梯度孙子，一阶的sobel算子和Prewitt算子以及二阶的拉普拉斯运算等。实际上，根据锐化的目的，可以采用多种方法来达到其效果。在此采用一种简单的锐化方法，即原像素+边缘像素平均值*系数。
g(x,y)=f(i,j)+k/N(f(x,y)-f(i,j))对图像上的每一点都是这样的。g（x,y)为锐化后的像素颜色值；N为邻域像素点；k为锐化系数。i，j属于当前像素点（x，y）的邻域。一般就是8个点啦。
代码如下：
//锐化
public static Bitmap sharpen(Bitmap b)
{
if (b == null)
{
MessageBox.Show("无图像可处理", "提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
return null;
}
string sp = Interaction.InputBox("请输入一个0~1之间的锐化参数", "锐化参数设置", "0.5", 100, 100);
if (sp == "" || Convert.ToSingle(sp) < 0 || Convert.ToSingle(sp) > 1)
{
MessageBox.Show("锐化参数必须在0~1之间", "提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
float val = Convert.ToSingle(sp);
int w = b.Width;
int h = b.Height;
try
{
Bitmap bmprtn = new Bitmap(w, h, PixelFormat.Format24bppRgb);
BitmapData srcData = b.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
BitmapData dstData = bmprtn.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);
unsafe
{
byte* pIn = (byte*)srcData.Scan0.ToPointer();
byte* pOut = (byte*)dstData.Scan0.ToPointer();
int stride = srcData.Stride;
byte* p;
for (int y = 0; y < h; y++)
{
for (int x = 0; x < w; x++)
{
if (x == 0 || x == w - 1 || y == 0 || y == h - 1)
{
pOut[0] = pIn[0];
pOut[1] = pIn[1];
pOut[2] = pIn[2];
}
else
{
int r1, r2, r3, r4, r5, r6, r7, r8, r0;
int g1, g2, g3, g4, g5, g6, g7, g8, g0;
int b1, b2, b3, b4, b5, b6, b7, b8, b0;
float vR, vG, vB;
p = pIn - stride - 3;
r1 = p[2];
g1 = p[1];
b1 = p[0];
p = pIn - stride;
r2 = p[2];
g2 = p[1];
b2 = p[0];
p = pIn - stride + 3;
r3 = p[2];
g3 = p[1];
b3 = p[0];
p = pIn - 3;
r4 = p[2];
g4 = p[1];
b4 = p[0];
p = pIn + 3;
r5 = p[2];
g5 = p[1];
b5 = p[0];
p = pIn + stride - 3;
r6 = p[2];
g6 = p[1];
b6 = p[0];
p = pIn + stride;
r7 = p[2];
g7 = p[1];
b7 = p[0];
p = pIn + stride + 3;
r8 = p[2];
g8 = p[1];
b8 = p[0];
p = pIn + stride + 3;
r8 = p[2];
g8 = p[1];
b8 = p[0];
p = pIn;
r0 = p[2];
g0 = p[1];
b0 = p[0];
vR = (float)r0 - (float)(r1 + r2 + r3 + r4 + r5 + r6 + r7 + r8) / 8;
vG = (float)g0 - (float)(g1 + g2 + g3 + g4 + g5 + g6 + g7 + g8) / 8;
vB = (float)b0 - (float)(b1 + b2 + b3 + b4 + b5 + b6 + b7 + b8) / 8;
vR = r0 + vR * val;
vG = g0 + vG * val;
vB = b0 + vB * val;
if (vR > 0)
{
vR = Math.Min(255, vR);
}
else
{
vR = Math.Max(0, vR);
}
if (vG > 0)
{
vG = Math.Min(255, vG);
}
else
{
vG = Math.Max(0, vG);
}
if (vB > 0)
{
vB = Math.Min(255, vB);
}
else
{
vB = Math.Max(0, vB);
}
pOut[0] = (byte)vB;
pOut[1] = (byte)vG;
pOut[2] = (byte)vR;
}
pIn += 3;
pOut += 3;
}
pIn += srcData.Stride - w * 3;
pOut += srcData.Stride - w * 3;
}
}
b.UnlockBits(srcData);
bmprtn.UnlockBits(dstData);
return bmprtn;
}
catch
{
return null;
}
}