C#图片灰度处理(位深度24→位深度8)C#图片二值化处理(位深度8→位深度1)

Posted 2022-03-26 aaronguo

C#图片灰度处理(位深度24→位深度8)

#region 灰度处理
        /// <summary>
        /// 将源图像灰度化，并转化为8位灰度图像。
        /// </summary>
        /// <param name="original"> 源图像。 </param>
        /// <returns> 8位灰度图像。 </returns>
        public static Bitmap RgbToGrayScale(Bitmap original)
        
            if (original != null)
            
                // 将源图像内存区域锁定
                Rectangle rect = new Rectangle(0, 0, original.Width, original.Height);
                BitmapData bmpData = original.LockBits(rect, ImageLockMode.ReadOnly,
                        PixelFormat.Format24bppRgb);

                // 获取图像参数
                int width = bmpData.Width;
                int height = bmpData.Height;
                int stride = bmpData.Stride;  // 扫描线的宽度,比实际图片要大
                int offset = stride - width * 3;  // 显示宽度与扫描线宽度的间隙
                IntPtr ptr = bmpData.Scan0;   // 获取bmpData的内存起始位置的指针
                int scanBytesLength = stride * height;  // 用stride宽度，表示这是内存区域的大小

                // 分别设置两个位置指针，指向源数组和目标数组
                int posScan = 0, posDst = 0;
                byte[] rgbValues = new byte[scanBytesLength];  // 为目标数组分配内存
                Marshal.Copy(ptr, rgbValues, 0, scanBytesLength);  // 将图像数据拷贝到rgbValues中
                // 分配灰度数组
                byte[] grayValues = new byte[width * height]; // 不含未用空间。
                // 计算灰度数组

                byte blue, green, red, YUI;



                for (int i = 0; i < height; i++)
                
                    for (int j = 0; j < width; j++)
                    

                        blue = rgbValues[posScan];
                        green = rgbValues[posScan + 1];
                        red = rgbValues[posScan + 2];
                        YUI = (byte)(0.229 * red + 0.587 * green + 0.144 * blue);
                        //grayValues[posDst] = (byte)((blue + green + red) / 3);
                        grayValues[posDst] = YUI;
                        posScan += 3;
                        posDst++;

                    
                    // 跳过图像数据每行未用空间的字节，length = stride - width * bytePerPixel
                    posScan += offset;
                

                // 内存解锁
                Marshal.Copy(rgbValues, 0, ptr, scanBytesLength);
                original.UnlockBits(bmpData);  // 解锁内存区域

                // 构建8位灰度位图
                Bitmap retBitmap = BuiltGrayBitmap(grayValues, width, height);
                return retBitmap;
            
            else
            
                return null;
            
        

        /// <summary>
        /// 用灰度数组新建一个8位灰度图像。
        /// </summary>
        /// <param name="rawValues"> 灰度数组(length = width * height)。 </param>
        /// <param name="width"> 图像宽度。 </param>
        /// <param name="height"> 图像高度。 </param>
        /// <returns> 新建的8位灰度位图。 </returns>
        private static Bitmap BuiltGrayBitmap(byte[] rawValues, int width, int height)
        
            // 新建一个8位灰度位图，并锁定内存区域操作
            Bitmap bitmap = new Bitmap(width, height, PixelFormat.Format8bppIndexed);
            BitmapData bmpData = bitmap.LockBits(new Rectangle(0, 0, width, height),
                 ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed);

            // 计算图像参数
            int offset = bmpData.Stride - bmpData.Width;        // 计算每行未用空间字节数
            IntPtr ptr = bmpData.Scan0;                         // 获取首地址
            int scanBytes = bmpData.Stride * bmpData.Height;    // 图像字节数 = 扫描字节数 * 高度
            byte[] grayValues = new byte[scanBytes];            // 为图像数据分配内存

            // 为图像数据赋值
            int posSrc = 0, posScan = 0;                        // rawValues和grayValues的索引
            for (int i = 0; i < height; i++)
            
                for (int j = 0; j < width; j++)
                
                    grayValues[posScan++] = rawValues[posSrc++];
                
                // 跳过图像数据每行未用空间的字节，length = stride - width * bytePerPixel
                posScan += offset;
            

            // 内存解锁
            Marshal.Copy(grayValues, 0, ptr, scanBytes);
            bitmap.UnlockBits(bmpData);  // 解锁内存区域

            // 修改生成位图的索引表，从伪彩修改为灰度
            ColorPalette palette;
            // 获取一个Format8bppIndexed格式图像的Palette对象
            using (Bitmap bmp = new Bitmap(1, 1, PixelFormat.Format8bppIndexed))
            
                palette = bmp.Palette;
            
            for (int i = 0; i < 256; i++)
            
                palette.Entries[i] = Color.FromArgb(i, i, i);
            
            // 修改生成位图的索引表
            bitmap.Palette = palette;

            return bitmap;
        
        #endregion

C#图片二值化处理(位深度8→位深度1)

#region 二值化

        #region Otsu阈值法二值化模块   

        /// <summary>   
        /// Otsu阈值   
        /// </summary>   
        /// <param name="b">位图流</param>   
        /// <returns></returns>   
        public Bitmap OtsuThreshold()
        
            // 图像灰度化   
            // b = Gray(b);   
            int width = bitmap.Width;
            int height = bitmap.Height;
            byte threshold = 0;
            int[] hist = new int[256];

            int AllPixelNumber = 0, PixelNumberSmall = 0, PixelNumberBig = 0;

            double MaxValue, AllSum = 0, SumSmall = 0, SumBig, ProbabilitySmall, ProbabilityBig, Probability;
            BitmapData bmpData = bitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);

            unsafe
            
                byte* p = (byte*)bmpData.Scan0;
                int offset = bmpData.Stride - width * 4;
                for (int j = 0; j < height; j++)
                
                    for (int i = 0; i < width; i++)
                    
                        hist[p[0]]++;
                        p += 4;
                    
                    p += offset;
                
                bitmap.UnlockBits(bmpData);
            
            //计算灰度为I的像素出现的概率   
            for (int i = 0; i < 256; i++)
            
                AllSum += i * hist[i];     //   质量矩   
                AllPixelNumber += hist[i];  //  质量       
            
            MaxValue = -1.0;
            for (int i = 0; i < 256; i++)
            
                PixelNumberSmall += hist[i];
                PixelNumberBig = AllPixelNumber - PixelNumberSmall;
                if (PixelNumberBig == 0)
                
                    break;
                

                SumSmall += i * hist[i];
                SumBig = AllSum - SumSmall;
                ProbabilitySmall = SumSmall / PixelNumberSmall;
                ProbabilityBig = SumBig / PixelNumberBig;
                Probability = PixelNumberSmall * ProbabilitySmall * ProbabilitySmall + PixelNumberBig * ProbabilityBig * ProbabilityBig;
                if (Probability > MaxValue)
                
                    MaxValue = Probability;
                    threshold = (byte)i;
                
            
            this.Threshoding(bitmap, threshold);
            bitmap = twoBit(bitmap);
            return bitmap; ;
         
        #endregion

        #region      固定阈值法二值化模块
        public Bitmap Threshoding(Bitmap b, byte threshold)
        
            int width = b.Width;
            int height = b.Height;
            BitmapData data = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
            unsafe
            
                byte* p = (byte*)data.Scan0;
                int offset = data.Stride - width * 4;
                byte R, G, B, gray;
                for (int y = 0; y < height; y++)
                
                    for (int x = 0; x < width; x++)
                    
                        R = p[2];
                        G = p[1];
                        B = p[0];
                        gray = (byte)((R * 19595 + G * 38469 + B * 7472) >> 16);
                        if (gray >= threshold)
                        
                            p[0] = p[1] = p[2] = 255;
                        
                        else
                        
                            p[0] = p[1] = p[2] = 0;
                        
                        p += 4;
                    
                    p += offset;
                
                b.UnlockBits(data);
                return b;

            

        
        #endregion

        #region 创建1位图像

        /// <summary>
        /// 创建1位图像
        /// </summary>
        /// <param name="srcBitmap"></param>
        /// <returns></returns>
        public Bitmap twoBit(Bitmap srcBitmap)
        
            int midrgb = Color.FromArgb(128, 128, 128).ToArgb();
            int stride;//简单公式((width/8)+3)&(~3)
            stride = (srcBitmap.Width % 8) == 0 ? (srcBitmap.Width / 8) : (srcBitmap.Width / 8) + 1;
            stride = (stride % 4) == 0 ? stride : ((stride / 4) + 1) * 4;
            int k = srcBitmap.Height * stride;
            byte[] buf = new byte[k];
            int x = 0, ab = 0;
            for (int j = 0; j < srcBitmap.Height; j++)
            
                k = j * stride;//因图像宽度不同、有的可能有填充字节需要跳越
                x = 0;
                ab = 0;
                for (int i = 0; i < srcBitmap.Width; i++)
                
                    //从灰度变单色（下法如果直接从彩色变单色效果不太好，不过反相也可以在这里控制）
                    if ((srcBitmap.GetPixel(i, j)).ToArgb() > midrgb)
                    
                        ab = ab * 2 + 1;
                    
                    else
                    
                        ab = ab * 2;
                    
                    x++;
                    if (x == 8)
                    
                        buf[k++] = (byte)ab;//每字节赋值一次，数组buf中存储的是十进制。
                        ab = 0;
                        x = 0;
                    
                
                if (x > 0)
                
                    //循环实现：剩余有效数据不满1字节的情况下须把它们移往字节的高位部分
                    for (int t = x; t < 8; t++) ab = ab * 2;
                    buf[k++] = (byte)ab;
                
            
            int width = srcBitmap.Width;
            int height = srcBitmap.Height;
            Bitmap dstBitmap = new Bitmap(width, height, PixelFormat.Format1bppIndexed);
            BitmapData dt = dstBitmap.LockBits(new Rectangle(0, 0, dstBitmap.Width, dstBitmap.Height), ImageLockMode.ReadWrite, dstBitmap.PixelFormat);
            Marshal.Copy(buf, 0, dt.Scan0, buf.Length);
            dstBitmap.UnlockBits(dt);
            return dstBitmap;
        

        #endregion

        #endregion