17.3.2.7 二值化（内存处理）

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二值化的算法请参看第17.3.1.5节。17.3.1.5 二值化（黑白）-CSDN博客

【例 17.48】二值化算法一。

        //黑白1
        private void btn2Color1_Click(object sender, EventArgs e)
        {
            Bitmap destImg = new Bitmap(sourceImg.Width, sourceImg.Height);
            BitmapData sourceData = sourceImg.LockBits(new Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
            BitmapData destData = destImg.LockBits(new Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);
            IntPtr pSource = sourceData.Scan0;
            int allBytes = sourceData.Stride * sourceData.Height;
            byte[] rgbvalues = new byte[allBytes];
            Marshal.Copy(pSource, rgbvalues, 0, allBytes);
 
            int pos = 0;
            int R, G, B;
            byte avgValue;
 
            for (int j = 0; j < sourceData.Height; j++)
            {
                for (int i = 0; i < sourceData.Width; i++)
                {
                    B = rgbvalues[pos];
                    G = rgbvalues[pos + 1];
                    R = rgbvalues[pos + 2];
                    avgValue = (byte)((B + G + R) / 3);
                    if (avgValue >= 128)
                        avgValue = 255;
                    else
                        avgValue = 0;
                    rgbvalues[pos] = avgValue; 
                    rgbvalues[pos + 1] = avgValue;
                    rgbvalues[pos + 2] = avgValue;
                    pos = pos + 3;
                }
                pos = pos + sourceData.Stride - sourceData.Width * 3;
            }
 
            IntPtr pDest = destData.Scan0;
            Marshal.Copy(rgbvalues, 0, pDest, allBytes);
            sourceImg.UnlockBits(sourceData);
            destImg.UnlockBits(destData);
            picDest.Image = destImg;
        }

【例 17.49】二值化算法二

      //黑白2
        private void btn2Color2_Click(object sender, EventArgs e)
        {
            Bitmap destImg = new Bitmap(sourceImg.Width, sourceImg.Height);
            BitmapData sourceData = sourceImg.LockBits(new Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
            BitmapData destData = destImg.LockBits(new Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);
            IntPtr pSource = sourceData.Scan0;
            int allBytes = sourceData.Stride * sourceData.Height;
            byte[] rgbvalues = new byte[allBytes];
            Marshal.Copy(pSource, rgbvalues, 0, allBytes);
 
            int pos = 0;
            int R, G, B;
 
            int[] HistGram = new int[256];
 
            for (int j = 0; j < sourceData.Height; j++)
            {
                for (int i = 0; i < sourceData.Width; i++)
                {
                    R = rgbvalues[pos + 2];
                    HistGram[R] += 1;
                    pos = pos + 3;
                }
                pos = pos + sourceData.Stride - sourceData.Width * 3;
            }
 
            int threshold;
 
            int allSum = 0;
            int allCount=0;
            for(int k= 0;k<= 255;k++)
            {
                allCount += HistGram[k];
                allSum += k * HistGram[k];
            }
 
            threshold = allSum / allCount;
            pos = 0;
            for (int j = 0; j < sourceData.Height; j++)
            {
               for (int i = 0; i < sourceData.Width; i++)
               {
                    R = rgbvalues[pos + 2];
                    if (R >= threshold)
                        R = 255;
                    else
                        R = 0;
                    rgbvalues[pos] = (byte)R;
                    rgbvalues[pos + 1] = (byte)R;
                    rgbvalues[pos + 2] = (byte)R;
                    pos = pos + 3;
                }
                pos = pos + sourceData.Stride - sourceData.Width * 3;
            }
 
 
            IntPtr pDest= destData.Scan0;
            Marshal.Copy(rgbvalues, 0, pDest, allBytes);
            sourceImg.UnlockBits(sourceData);
            destImg.UnlockBits(destData);
            picDest.Image = destImg;
        }

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