图像特效---旋转模糊滤镜

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本文介绍一种旋转模糊滤镜的实现算法。

旋转模糊主要特点是：整张图像围绕一个中心点做旋转变换，同时有个控制旋转程度的变量和一个控制模糊程度的变量，来完成这个效果。图像中距离中心点越近，旋转和模糊的程度都越小，反之，越大。

假设中心点O坐标为(cenX,cenY)，当前点位置为P(x,y)：

1，PO距离Dis=Math.Sqrt((y - cenY) * (y - cenY) + (x - cenX) * (x - cenX));

2，PO和水平方向夹角angle=Math.Atan2((double)(y - cenY), (double)(x - cenX));

3，当前点P对应的旋转后新的坐标newX,newY计算：

newX = Dis * Math.Cos(angle) + cenX;

newY = Dis * Math.Sin(angle) + cenY;

下面给出完整的C#代码：

///

/// Rotate Blur

///

/// Source image.

/// The X position of Blur.

/// The Y position of Blur.

/// The intensity of blur,0-100.

/// The result image.

private Bitmap RotateBlurProcess(Bitmap srcBitmap, int cenX, int cenY, int intensity)

{

Bitmap a = new Bitmap(srcBitmap);

int w = a.Width;

int h = a.Height;

cenX = Math.Min(w - 1, Math.Max(0, cenX));

cenY = Math.Min(h - 1, Math.Max(0, cenY));

Bitmap dst = new Bitmap(w, h);

System.Drawing.Imaging.BitmapData srcData = a.LockBits(new Rectangle(0, 0, w, h), System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

System.Drawing.Imaging.BitmapData dstData = dst.LockBits(new Rectangle(0, 0, w, h), System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

unsafe

{

byte* pIn = (byte*)srcData.Scan0.ToPointer();

byte* pOut = (byte*)dstData.Scan0.ToPointer();

byte* p = null;

int stride = srcData.Stride - w * 4;

int newX = 0, newY = 0;

double angle = 0;

double temp = 0, r = 0, g = 0, b = 0;

for (int y = 0; y < h; y++)

{

for (int x = 0; x < w; x++)

{

r = 0;

g = 0;

b = 0;

temp = Math.Sqrt((y - cenY) * (y - cenY) + (x - cenX) * (x - cenX));

angle = Math.Atan2((double)(y - cenY), (double)(x - cenX));

for (int n = 0; n < intensity; n++)

{

angle = angle + 0.005;

newX = (int)(temp * Math.Cos(angle) + (double)cenX);

newY = (int)(temp * Math.Sin(angle) + (double)cenY);

newX = Math.Min(w - 1, Math.Max(0, newX));

newY = Math.Min(h - 1, Math.Max(0, newY));

p = pIn + newY * srcData.Stride + newX * 4;

b = b + p[0];

g = g + p[1];

r = r + p[2];

}

b = Math.Min(255, Math.Max(0, b / intensity));

g = Math.Min(255, Math.Max(0, g / intensity));

r = Math.Min(255, Math.Max(0, r / intensity));

pOut[0] = (byte)b;

pOut[1] = (byte)g;

pOut[2] = (byte)r;

pOut[3] = (byte)255;

pOut += 4;

}

pOut += stride;

}

a.UnlockBits(srcData);

dst.UnlockBits(dstData);

}

return dst;

}

最后，看下效果图：

原图

效果图

demo link: 点击打开链接

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