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)

梦里梦外; 2021-12-07 11:51 727阅读 0赞

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

转载于:https://www.cnblogs.com/aaronguo/p/11150243.html