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

 学海无涯GL 2013-04-10

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

作者：王先荣

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。

View Code
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/// <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;
}

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：
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/// <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;
    }
}

总算，写完了，打字真累啊。

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