OpenCv，EmguCv及.net之间的互动(The Interaction of OpenCv, EmguCv AND .net)

http://www.cnblogs.com/xrwang/archive/2010/01/26/TheInteractionOfOpenCv-EmguCvANDDotNet.html

前言

在.net中使用OpenCv和EmguCv时，必须在三者支持的图像格式之间进行转换。.net中用Bitmap类来承载图像，OpenCv中用IplImage指针来承载图像，EmguCv中用Image<TColor,TDepth>来承载图像。本文主要讲述如何在IplImage、Image<TColor,TDepth>和Bitmap之间转换。

IplImage  <=>  MIplImage

MIplImage是IplImage中的托管实现，它是.net与OpenCv之间沟通的桥梁。IplImage指针和MIplImage之间的转换主要用到了Marshal类中的PtrToStructure、StructureToPtr、AllocHGlobal和FreeHGlobal这几个静态方法。

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/// <summary> /// 将MIplImage结构转换到IplImage指针； /// 注意：指针在使用完之后必须用Marshal.FreeHGlobal方法释放。 /// </summary> /// <param name="mi">MIplImage对象</param> /// <returns>返回IplImage指针</returns> public static IntPtr MIplImageToIplImagePointer(MIplImage mi) {     IntPtr ptr = Marshal.AllocHGlobal(mi.nSize);     Marshal.StructureToPtr(mi, ptr, false);     return ptr; }   /// <summary> /// 将IplImage指针转换成MIplImage结构 /// </summary> /// <param name="ptr">IplImage指针</param> /// <returns>返回MIplImage结构</returns> public static MIplImage IplImagePointerToMIplImage(IntPtr ptr) {     return (MIplImage)Marshal.PtrToStructure(ptr, typeof(MIplImage)); }

需要注意的是，不能使用 MIplImage * pmi=(MIplImage *)ptr.ToPointer();  和  IntPtr ptr=&mi; 之类的写法。

IplImage  <=>  Image<TColor,TDepth>

用了MIplImage的辅助，我们可以很容易实现IplImage指针和Image<TColor,TDepth>之间的转换。

        /// <summary>
        /// 将IplImage指针转换成Emgucv中的Image对象；
        /// 注意：这里需要您自己根据IplImage中的depth和nChannels来决定
        /// </summary>
        /// <typeparam name="TColor">Color type of this image (either Gray, Bgr, Bgra, Hsv, Hls, Lab, Luv, Xyz or Ycc)</typeparam>
        /// <typeparam name="TDepth">Depth of this image (either Byte, SByte, Single, double, UInt16, Int16 or Int32)</typeparam>
        /// <param name="ptr">IplImage指针</param>
        /// <returns>返回Image对象</returns>
        public static Image<TColor, TDepth> IplImagePointerToEmgucvImage<TColor, TDepth>(IntPtr ptr)
            where TColor : struct, IColor
            where TDepth : new()
        {
            MIplImage mi = IplImagePointerToMIplImage(ptr);
            return new Image<TColor, TDepth>(mi.width, mi.height, mi.widthStep, mi.imageData);
        }

        /// <summary>
        /// 将IplImage指针转换成Emgucv中的IImage接口；
        /// 1通道对应灰度图像，3通道对应BGR图像，4通道对应BGRA图像。
        /// 注意：3通道可能并非BGR图像，而是HLS,HSV等图像
        /// </summary>
        /// <param name="ptr">IplImage指针</param>
        /// <returns>返回IImage接口</returns>
        public static IImage IplImagePointToEmgucvIImage(IntPtr ptr)
        {
            MIplImage mi = IplImagePointerToMIplImage(ptr);
            Type tColor;
            Type tDepth;
            string unsupportedDepth = "不支持的像素位深度IPL_DEPTH";
            string unsupportedChannels = "不支持的通道数（仅支持1，2，4通道）";
            switch (mi.nChannels)
            {
                case 1:
                    tColor = typeof(Gray);
                    switch (mi.depth)
                    {
                        case IPL_DEPTH.IPL_DEPTH_8U:
                            tDepth = typeof(Byte);
                            return new Image<Gray, Byte>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_16U:
                            tDepth=typeof(UInt16);
                            return new Image<Gray, UInt16>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_16S:
                            tDepth = typeof(Int16);
                            return new Image<Gray, Int16>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_32S:
                            tDepth = typeof(Int32);
                            return new Image<Gray, Int32>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_32F:
                            tDepth = typeof(Single);
                            return new Image<Gray, Single>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_64F:
                            tDepth = typeof(Double);
                            return new Image<Gray, Double>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        default:
                            throw new NotImplementedException(unsupportedDepth);
                    }
                case 3:
                    tColor = typeof(Bgr);
                    switch (mi.depth)
                    {
                        case IPL_DEPTH.IPL_DEPTH_8U:
                            tDepth = typeof(Byte);
                            return new Image<Bgr, Byte>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_16U:
                            tDepth = typeof(UInt16);
                            return new Image<Bgr, UInt16>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_16S:
                            tDepth = typeof(Int16);
                            return new Image<Bgr, Int16>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_32S:
                            tDepth = typeof(Int32);
                            return new Image<Bgr, Int32>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_32F:
                            tDepth = typeof(Single);
                            return new Image<Bgr, Single>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_64F:
                            tDepth = typeof(Double);
                            return new Image<Bgr, Double>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        default:
                            throw new NotImplementedException(unsupportedDepth);
                    }
                case 4:
                    tColor = typeof(Bgra);
                    switch (mi.depth)
                    {
                        case IPL_DEPTH.IPL_DEPTH_8U:
                            tDepth = typeof(Byte);
                            return new Image<Bgra, Byte>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_16U:
                            tDepth = typeof(UInt16);
                            return new Image<Bgra, UInt16>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_16S:
                            tDepth = typeof(Int16);
                            return new Image<Bgra, Int16>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_32S:
                            tDepth = typeof(Int32);
                            return new Image<Bgra, Int32>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_32F:
                            tDepth = typeof(Single);
                            return new Image<Bgra, Single>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        case IPL_DEPTH.IPL_DEPTH_64F:
                            tDepth = typeof(Double);
                            return new Image<Bgra, Double>(mi.width, mi.height, mi.widthStep, mi.imageData);
                        default:
                            throw new NotImplementedException(unsupportedDepth);
                    }
                default:
                    throw new NotImplementedException(unsupportedChannels);
            }
        }

        /// <summary>
        /// 将Emgucv中的Image对象转换成IplImage指针；
        /// </summary>
        /// <typeparam name="TColor">Color type of this image (either Gray, Bgr, Bgra, Hsv, Hls, Lab, Luv, Xyz or Ycc)</typeparam>
        /// <typeparam name="TDepth">Depth of this image (either Byte, SByte, Single, double, UInt16, Int16 or Int32)</typeparam>
        /// <param name="image">Image对象</param>
        /// <returns>返回IplImage指针</returns>
        public static IntPtr EmgucvImageToIplImagePointer<TColor, TDepth>(Image<TColor, TDepth> image)
            where TColor : struct, IColor
            where TDepth : new()
        {
            return image.Ptr;//IplImage*,CvCapture*等指针在C#中都用IntPtr来代替，且其中没有cvGetMCvSize函数，故用cvGetImageROI来暂时代替
        }

Image<TColor,TDepth>  <=>  Bitmap

EmguCv中已经实现了这二者之间的转换，分别是Image<TColor,TDepth>类的下列成员：

(1)public Bitmap Bitmap { get; set; }

该属性可以获取或者设置位图；对于Image<Gray, Byte>, Image<Bgr, Byte> 和 Image<Bgra, Byte>这三种情况效率很高，因为Image<TColor,TDepth>和Bitmap共享数据内存。

(2)public Bitmap ToBitmap(int width,int height)及public Bitmap ToBitmap()方法

(3)public Image(Bitmap bmp)

(4)public Image(int width,int height,int stride,IntPtr scan0)

这个构造函数几乎是万能的，只要您清楚图像的内存分布，以及想要的目的。

IplImage  <=>  Bitmap

    IplImage指针和Bitmap间的转换有两种方式，第一种是利用Image<TColor,TDepth>作媒介；第二种是自己写转换的方法，例如我写的下列代码：

        /// <summary>
        /// 将IplImage指针转换成位图对象；
        /// 对于不支持的像素格式，可以先使用cvCvtColor函数转换成支持的图像指针
        /// </summary>
        /// <param name="ptr">IplImage指针</param>
        /// <returns>返回位图对象</returns>
        public static Bitmap IplImagePointerToBitmap(IntPtr ptr)
        {
            MIplImage mi = IplImagePointerToMIplImage(ptr);
            PixelFormat pixelFormat;    //像素格式
            string unsupportedDepth = "不支持的像素位深度IPL_DEPTH";
            string unsupportedChannels = "不支持的通道数（仅支持1，2，4通道）";
            switch(mi.nChannels)
            {
                case 1:
                    switch (mi.depth)
                    {
                        case IPL_DEPTH.IPL_DEPTH_8U:
                            pixelFormat = PixelFormat.Format8bppIndexed;
                            break;
                        case IPL_DEPTH.IPL_DEPTH_16U:
                            pixelFormat = PixelFormat.Format16bppGrayScale;
                            break;
                        default:
                            throw new NotImplementedException(unsupportedDepth);
                    }
                    break;
                case 3:
                    switch (mi.depth)
                    {
                        case IPL_DEPTH.IPL_DEPTH_8U:
                            pixelFormat = PixelFormat.Format24bppRgb;
                            break;
                        case IPL_DEPTH.IPL_DEPTH_16U:
                            pixelFormat = PixelFormat.Format48bppRgb;
                            break;
                        default:
                            throw new NotImplementedException(unsupportedDepth);
                    }
                    break;
                case 4:
                    switch (mi.depth)
                    {
                        case IPL_DEPTH.IPL_DEPTH_8U:
                            pixelFormat = PixelFormat.Format32bppArgb;
                            break;
                        case IPL_DEPTH.IPL_DEPTH_16U:
                            pixelFormat = PixelFormat.Format64bppArgb;
                            break;
                        default:
                            throw new NotImplementedException(unsupportedDepth);
                    }
                    break;
                default:
                    throw new NotImplementedException(unsupportedChannels);

            }
            Bitmap bitmap = new Bitmap(mi.width, mi.height, mi.widthStep, pixelFormat, mi.imageData);
            //对于灰度图像，还要修改调色板
            if (pixelFormat == PixelFormat.Format8bppIndexed)
                SetColorPaletteOfGrayscaleBitmap(bitmap);
            return bitmap;
        }

        /// <summary>
        /// 将位图转换成IplImage指针
        /// </summary>
        /// <param name="bitmap">位图对象</param>
        /// <returns>返回IplImage指针</returns>
        public static IntPtr BitmapToIplImagePointer(Bitmap bitmap)
        {
            IImage iimage = null;
            switch (bitmap.PixelFormat)
            {
                case PixelFormat.Format8bppIndexed:
                    iimage = new Image<Gray, Byte>(bitmap);
                    break;
                case PixelFormat.Format16bppGrayScale:
                    iimage = new Image<Gray, UInt16>(bitmap);
                    break;
                case PixelFormat.Format24bppRgb:
                    iimage = new Image<Bgr, Byte>(bitmap);
                    break;
                case PixelFormat.Format32bppArgb:
                    iimage = new Image<Bgra, Byte>(bitmap);
                    break;
                case PixelFormat.Format48bppRgb:
                    iimage = new Image<Bgr, UInt16>(bitmap);
                    break;
                case PixelFormat.Format64bppArgb:
                    iimage = new Image<Bgra, UInt16>(bitmap);
                    break;
                default:
                    Image<Bgra, Byte> tmp1 = new Image<Bgra, Byte>(bitmap.Size);
                    Byte[, ,] data = tmp1.Data;
                    for (int i = 0; i < bitmap.Width; i++)
                    {
                        for (int j = 0; j < bitmap.Height; j++)
                        {
                            Color color = bitmap.GetPixel(i, j);
                            data[j, i, 0] = color.B;
                            data[j, i, 1] = color.G;
                            data[j, i, 2] = color.R;
                            data[j, i, 3] = color.A;
                        }
                    }
                    iimage = tmp1;
                    break;
            }
            return iimage.Ptr;
        }

        /// <summary>
        /// 设置256级灰度位图的调色板
        /// </summary>
        /// <param name="bitmap"></param>
        public static void SetColorPaletteOfGrayscaleBitmap(Bitmap bitmap)
        {
            PixelFormat pixelFormat = bitmap.PixelFormat;
            if (pixelFormat == PixelFormat.Format8bppIndexed)
            {
                ColorPalette palette = bitmap.Palette;
                for (int i = 0; i < palette.Entries.Length; i++)
                    palette.Entries[i] = Color.FromArgb(255, i, i, i);
                bitmap.Palette = palette;
            }
        }