图像特效---挤压(Pinch)滤镜

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Pinch滤镜

Pinch滤镜是通过坐标变换来实现以某个点(cenX,cenY)为中心，某个半径R内图像向其挤压变形的效果。实现这个滤镜的算法很多，主要是数学公式的不同，大家可以自行设计，这里给个代码示例，大家可以直接使用。

代码如下：

///

/// Pinch Filter

///

/// Source image.

/// The X position of sun.

/// The Y position of sun.

/// The result image.

private Bitmap PinchFilterProcess(Bitmap srcBitmap, int cenX, int cenY)

{

Bitmap a = new Bitmap(srcBitmap);

int w = a.Width;

int h = a.Height;

int radius = 0;

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 sWidth = srcData.Stride;

int stride = sWidth - w * 4;

int offsetX = 0, offsetY = 0;

int newX = 0, newY = 0;

double radian = 0,degree = 10;

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

{

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

{

offsetX = x - cenX;

offsetY = y - cenY;

radian = Math.Atan2(offsetY, offsetX);

radius = (int)(Math.Sqrt(offsetX * offsetX + offsetY * offsetY));

radius = (int)(Math.Sqrt(radius) * degree);

newX = (int)(radius * Math.Cos(radian)) + cenX;

newY = (int)(radius * Math.Sin(radian)) + 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;

pOut[0] = (byte)p[0];

pOut[1] = (byte)p[1];

pOut[2] = (byte)p[2];

pOut[3] = (byte)255;

pOut += 4;

}

pOut += stride;

}

a.UnlockBits(srcData);

dst.UnlockBits(dstData);

}

return dst;

}

效果图如下：

原图

Pinch滤镜效果图

demo：http://www.zealfilter.com/forum.php?mod=viewthread&tid=55&extra=page%3D2

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