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