PhotoShop算法原理解析系列-像素化-碎片

private void CmdFragment_Click(object sender, EventArgs e)
{ int X, Y, Z, XX, YY; int Width, Height, Stride; int Speed, Index; int SumR, SumG, SumB;
 Bitmap Bmp = (Bitmap)Pic.Image; if (Bmp.PixelFormat != PixelFormat.Format24bppRgb) throw new Exception("不支持的图像格式.");

 Width = Bmp.Width; Height = Bmp.Height; Stride = (int)((Bmp.Width * 3 + 3) & 0XFFFFFFFC); byte[] ImageData = new byte[Stride * Height]; // 用于保存图像数据，（处理前后的都为他)
 byte[] ImageDataC = new byte[Stride * Height]; // 用于保存克隆的图像数据
 int[] OffsetX = new int[] { 4, -4, -4, 4 }; // 每个点的偏移量
 int[] OffsetY = new int[] { -4, -4, 4, 4 }; fixed (byte* P = &ImageData[0], CP = &ImageDataC[0])
 { byte* DataP = P, DataCP = CP;
 BitmapData BmpData = new BitmapData();
 BmpData.Scan0 = (IntPtr)DataP; // 设置为字节数组的的第一个元素在内存中的地址
 BmpData.Stride = Stride;
 Bmp.LockBits(new Rectangle(0, 0, Bmp.Width, Bmp.Height), ImageLockMode.ReadWrite | ImageLockMode.UserInputBuffer, PixelFormat.Format24bppRgb, BmpData);

 Stopwatch Sw = new Stopwatch(); // 只获取计算用时 Sw.Start();
 System.Buffer.BlockCopy(ImageData, 0, ImageDataC, 0, Stride * Height); // 填充克隆数据 

 for (Y = 0; Y < Height; Y++)
 {
 Speed = Y * Stride; for (X = 0; X < Width; X++)
 {
 SumB = 0; SumG = 0; SumR = 0; for (Z = 0; Z < 4; Z++) // 累积取样点的取样和 {
 XX = X + OffsetX[Z];
 YY = Y + OffsetY[Z]; if (XX < 0) // 注意越界
 XX = 0; else if (XX >= Width)
 XX = Width - 1; if (YY < 0)
 YY = 0; else if (YY >= Height)
 YY = Height - 1;
 Index = YY * Stride + XX * 3;
 SumB += DataCP[Index];
 SumG += DataCP[Index + 1];
 SumR += DataCP[Index + 2];
 }

 DataP[Speed] = (byte)((SumB+2) >> 2); // 求平均值(Sum+2)/4,为什么要+2，就为了四舍五入。比如如果计算

while (XX >= Width)
 XX = XX - Width;while (XX < 0)
 XX = XX + Width;while (YY >= Height)
 YY = YY - Height;while (YY < 0)
 YY = YY + Height;

 if (XX >= 0 && XX < Width && YY >= 0 && YY < Height)
 {
 // 累加计算
 }