OpenCV(EmguCV)2.1新特性介绍之图像差异StereoSGBM与设置窗口属性SetWindowProperty(StereoSGBM Of OpenCV 2.1)

作者：王先荣

    上次介绍了OpenCV2.1中新增的图像分割算法GrabCut，本文将介绍StereoSGBM与SetWindowProperty。其中StereoSGBM用于计算两幅图像间的差异图，跟已有的StereoBM和StereoGC作用一样，算法不同而已；SetWindowProperty用于设置窗口的属性，目前仅可用于设置全屏属性。

比较图像间的差异StereoSGBM
    StereoSGBM用于计算两幅图像间的差异图，在OpenCV的在线文档中有非常详细的介绍，地址是：“http://opencv.willowgarage.com/documentation/cpp/camera_calibration_and_3d_reconstruction.html#stereosgbm”。参数非常多，如果不使用默认的参数，需要仔细查看每个参数的说明，以免出错。OpenCV的具体实现在命名空间cv中的StereoSGBM类，目前还没有对应的C风格封装；EmguCV将其封装在StereoSGBM类中。
    StereoSGBM除了参数很多之外，使用起来蛮简单的，如下所示：

//创建StereoSGBM对象
StereoSGBM sgbm = new StereoSGBM((int)nudMinDisparity.Value, (int)nudNumDisparities.Value, (int)nudSADWindowSize.Value, (int)nudP1.Value,
    (int)nudP2.Value, (int)nudDisp12MaxDiff.Value, (int)nudPreFilterCap.Value, (int)nudUniquenessRatio.Value,
    (int)nudSpeckleWindowSize.Value, (int)nudSpeckleRange.Value, chkFullDP.Checked);
//查找两幅图像间的相关性（差异）
sgbm.FindStereoCorrespondence(leftImage, rightImage, disparityImage);
//显示结果
pbDisparity.Image = disparityImage.Bitmap;
//释放资源
sgbm.Dispose(); 

完整的示例（附带了StereoBM和StereoGC的示例）请看：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
using System.Runtime.InteropServices;
using Emgu.CV;
using Emgu.CV.CvEnum;
using Emgu.CV.Structure;

namespace NewFeaturesOfOpenCV2._1
{
    public partial class FormStereoCorrespondence : Form
    {
        //私有成员
        private string leftImageFileName = "wky_sls_2272x1704.jpg";     //左边的图像文件名
        private string rightImageFileName = "wky_sls_2272x1704_2.jpg";  //右边的图像文件名
        private Image<Gray, Byte> leftImage = null;                     //左边的灰度图像
        private Image<Gray, Byte> rightImage = null;                    //右边的灰度图像
        private Image<Gray, Int16> disparityImage = null;               //差异图像
        private Stopwatch sw = new Stopwatch();                         //计时器

        public FormStereoCorrespondence()
        {
            InitializeComponent();
        }

        //设置SGBM的默认参数
        private void btnFillDefaultParameters_Click(object sender, EventArgs e)
        {
            nudSADWindowSize.Value = 3;
            nudP1.Value = 0;
            nudP2.Value = 0;
            nudDisp12MaxDiff.Value = 0;
            nudPreFilterCap.Value = 0;
            nudUniquenessRatio.Value = 0;
            nudSpeckleWindowSize.Value = 0;
            nudSpeckleRange.Value = 0;
            chkFullDP.Checked = false;
        }

        //设置SGBM的推荐参数
        private void btnFillRecommendedParameters_Click(object sender, EventArgs e)
        {
            nudUniquenessRatio.Value = 5;
            nudSpeckleWindowSize.Value = 50;
            nudSpeckleRange.Value = 16;
        }

        //窗体加载时
        private void FormStereoCorrespondence_Load(object sender, EventArgs e)
        {
            //设置提示
            toolTip.SetToolTip(nudNumDisparities, "必须大于0，且能被16除尽");
            toolTip.SetToolTip(nudSADWindowSize, "缺省为0；如果指定则必须是正奇数，推荐值为3～11");
            toolTip.SetToolTip(nudP1, "缺省为0；推荐值为8*number_of_image_channels*SADWindowSize*SADWindowSize");
            toolTip.SetToolTip(nudP2, "缺省为0；如果指定则P2>P1，推荐值为32*number_of_image_channels*SADWindowSize*SADWindowSize");
            toolTip.SetToolTip(nudDisp12MaxDiff, "如果设置为负值，则跳过左右差异检查");
            toolTip.SetToolTip(nudUniquenessRatio, "缺省为0，推荐值为5～15");
            toolTip.SetToolTip(nudSpeckleWindowSize, "缺省为0，推荐值为50～200");
            toolTip.SetToolTip(nudSpeckleRange, "缺省为0；如果指定则必须是能被16整除的正数，推荐值为16或者32");
            //初始化图像
            InitImage(true);
            InitImage(false);
        }

        //加载图像1
        private void btnLoadLeftImage_Click(object sender, EventArgs e)
        {
            LoadImage(true);
        }

        //加载图像2
        private void btnLoadRightImage_Click(object sender, EventArgs e)
        {
            LoadImage(false);
        }

        /// <summary>
        /// 加载图像
        /// </summary>
        /// <param name="isLeft">是左边的图像吗？</param>
        private void LoadImage(bool isLeft)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.CheckFileExists = true;
            ofd.DefaultExt = "jpg";
            ofd.Filter = "图片文件|*.jpg;*.png;*.bmp|所有文件|*.*";
            if (ofd.ShowDialog(this) == DialogResult.OK)
            {
                if (ofd.FileName != "")
                {
                    if (isLeft)
                        leftImageFileName = ofd.FileName;
                    else
                        rightImageFileName = ofd.FileName;
                    InitImage(isLeft);
                }
            }
            ofd.Dispose();
        }

        /// <summary>
        /// 初始化图像
        /// </summary>
        /// <param name="isLeft">是左边的图像吗？</param>
        private void InitImage(bool isLeft)
        {
            if (isLeft)
            {
                Image<Bgr, Byte> image = new Image<Bgr, byte>(leftImageFileName);
                pbLeft.Image = image.Bitmap;
                if (leftImage != null)
                    leftImage.Dispose();
                leftImage = image.Convert<Gray, Byte>();
                if (disparityImage != null)
                    disparityImage.Dispose();
                disparityImage = new Image<Gray, short>(leftImage.Size);
                image.Dispose();
            }
            else
            {
                Image<Bgr, Byte> image = new Image<Bgr, byte>(rightImageFileName);
                pbRight.Image = image.Bitmap;
                if (rightImage != null)
                    rightImage.Dispose();
                rightImage = image.Convert<Gray, Byte>();
                image.Dispose();
            }
        }

        //开始计算
        private void btnCalc_Click(object sender, EventArgs e)
        {
            if (leftImage.Size != rightImage.Size)
            {
                MessageBox.Show(this, "两幅图像的尺寸不一致，不能比较。", "错误提示");
                return;
            }
            if (tcStereo.SelectedTab == tpStereoSGBM)
            {
                StereoSGBM sgbm = new StereoSGBM((int)nudMinDisparity.Value, (int)nudNumDisparities.Value, (int)nudSADWindowSize.Value, (int)nudP1.Value,
                    (int)nudP2.Value, (int)nudDisp12MaxDiff.Value, (int)nudPreFilterCap.Value, (int)nudUniquenessRatio.Value,
                    (int)nudSpeckleWindowSize.Value, (int)nudSpeckleRange.Value, chkFullDP.Checked);
                sw.Stop();
                sw.Start();
                sgbm.FindStereoCorrespondence(leftImage, rightImage, disparityImage);
                sw.Stop();
                pbDisparity.Image = disparityImage.Bitmap;
                sgbm.Dispose();
                lblStatus.Text = string.Format("SGBM比较耗时{0:F04}毫秒。", sw.ElapsedMilliseconds);
            }
            else if (tcStereo.SelectedTab == tpStereoBM)
            {
                STEREO_BM_TYPE type = cbBMType.Text == "BASIC" ? STEREO_BM_TYPE.BASIC : (cbBMType.Text == "FISH_EYE" ? STEREO_BM_TYPE.FISH_EYE : STEREO_BM_TYPE.NARROW);
                StereoBM bm = new StereoBM(type, (int)nudBMNumberOfDisparities.Value);
                sw.Stop();
                sw.Start();
                bm.FindStereoCorrespondence(leftImage, rightImage, disparityImage);
                sw.Stop();
                pbDisparity.Image = disparityImage.Bitmap;
                bm.Dispose();
                lblStatus.Text = string.Format("BM比较耗时{0:F04}毫秒。", sw.ElapsedMilliseconds);
            }
            else if (tcStereo.SelectedTab == tpStereoGC)
            {
                StereoGC gc = new StereoGC((int)nudGCNumberOfDisparities.Value, (int)nudGCMaxIters.Value);
                Image<Gray, Int16> rightDisparityImage = new Image<Gray, short>(leftImage.Size);
                sw.Stop();
                sw.Start();
                gc.FindStereoCorrespondence(leftImage, rightImage, disparityImage, rightDisparityImage);
                sw.Stop();
                CvInvoke.cvConvertScale(rightDisparityImage.Ptr, rightDisparityImage.Ptr, 16d, 0d);
                CvInvoke.cvConvertScale(disparityImage.Ptr, disparityImage.Ptr, -16d, 0d);
                pbDisparity.Image = rightDisparityImage.Bitmap;
                rightDisparityImage.Dispose();
                gc.Dispose();
                lblStatus.Text = string.Format("GC比较耗时{0:F04}毫秒。", sw.ElapsedMilliseconds);
            }
        }

        //关闭窗口时
        private void FormStereoCorrespondence_FormClosed(object sender, FormClosedEventArgs e)
        {
            //释放资源
            if (leftImage != null)
                leftImage.Dispose();
            if (rightImage != null)
                rightImage.Dispose();
            if (disparityImage != null)
                disparityImage.Dispose();
        }
    }
}

设置窗口属性SetWindowProperty
    目前只能用SetWindowProperty来设置窗口的全屏属性——全屏或者普通窗口。其实OpenCV2.1中还增加了一个名为cvGetWindowProperty的函数，用于获取窗口的属性，更新说明中没有提到而已。由于目前还没有这个函数的相关文档，我就详细点说说。
1.函数原型、参数说明及提示
void cvSetWindowProperty(const char* name, int prop_id, double prop_value)
作用：设置窗口的属性
返回值：无
参数：
name——窗口名称，对应于用cvNamedWindow创建窗口时使用的名称；
prop_id——属性id，目前有两种属性：CV_WND_PROP_FULLSCREEN    （=0）和CV_WND_PROP_AUTOSIZE（=1），但是仅CV_WND_PROP_FULLSCREEN有用；
prop_value——属性值，如果设置全屏属性，则该值可能有：CV_WINDOW_NORMAL（=0）和CV_WINDOW_FULLSCREEN    （=1）。
备注：（1）cvSetWindowProperty目前只能用于设置窗口的全屏属性；（2）在设置该属性前，要求窗口不能是AUTOSIZE的，否则设置无效；（3）基于第2点原因，在创建窗口时不能省略flag参数（即不能使用其默认值CV_WINDOW_AUTOSIZE）；（4）由于EmguCV封装的CvInvoke.cvNamedWindow强制使用了AUTOSIZE参数，因此不能使用它来创建窗口，需要自行进行P/Invoke调用；（5）OpenCV2.1更新文档中的使用示例是错误的，不要模仿。

double cvGetWindowProperty(const char* name, int prop_id)
作用：获取窗口的属性
返回值：返回窗口的属性值
参数：同cvSetWindowProperty

2.示例
您可以按如下所示使用cvSetWindowProperty：

cvSetWindowProperty(windowName, CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);

完整的示例请看：

        //全屏窗口
        private void btnSetWindowProperty_Click(object sender, EventArgs e)
        {
            Image<Bgr, Byte> image = new Image<Bgr, byte>("wky_qiao_2272x1704.jpg");
            string windowName = "stereoGC left disparity";
            cvNamedWindow(windowName, 0);
            cvResizeWindow(windowName, 640, 480);
            cvMoveWindow(windowName, 100, 100);
            cvSetWindowProperty(windowName, CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
            CvInvoke.cvShowImage(windowName, image.Ptr);
            CvInvoke.cvWaitKey(0);
            CvInvoke.cvDestroyWindow(windowName);
            image.Dispose();
        }

        //定义跟窗口相关的常量
        public const int CV_WND_PROP_FULLSCREEN = 0;
        public const int CV_WND_PROP_AUTOSIZE = 1;
        public const double CV_WINDOW_NORMAL = 0;
        public const double CV_WINDOW_FULLSCREEN = 1;
        public const int CV_WINDOW_AUTOSIZE = 1;
        //跟窗口有关的P/Invoke调用
        //设置窗口属性，目前只能设置CV_WND_PROP_FULLSCREEN
        [System.Runtime.InteropServices.DllImportAttribute("highgui210.dll", EntryPoint = "cvSetWindowProperty")]
        public static extern void cvSetWindowProperty([System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string name, int prop_id, double prop_value);
        //调整窗口的尺寸
        [System.Runtime.InteropServices.DllImportAttribute("highgui210.dll", EntryPoint = "cvResizeWindow")]
        public static extern void cvResizeWindow([System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string name, int width, int height);
        //移动窗口
        [System.Runtime.InteropServices.DllImportAttribute("highgui210.dll", EntryPoint = "cvMoveWindow")]
        public static extern void cvMoveWindow([System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string name, int x, int y);
        //创建指定名称的窗口
        [System.Runtime.InteropServices.DllImportAttribute("highgui210.dll", EntryPoint = "cvNamedWindow")]
        public static extern int cvNamedWindow([System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string name, int flags);
        //获取窗口对应的句柄HWnd
        [System.Runtime.InteropServices.DllImportAttribute("highgui210.dll", EntryPoint = "cvGetWindowHandle")]
        public static extern System.IntPtr cvGetWindowHandle([System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string name);
        //获取指定句柄对应的窗口名称
        [System.Runtime.InteropServices.DllImportAttribute("highgui210.dll", EntryPoint = "cvGetWindowName")]
        public static extern System.IntPtr cvGetWindowName(System.IntPtr windowHandle);
        //获取窗口的属性
        [System.Runtime.InteropServices.DllImportAttribute("highgui210.dll", EntryPoint = "cvGetWindowProperty")]
        public static extern double cvGetWindowProperty([System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string name, int prop_id);

    }

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