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：
StereoSGBM完整示例
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：
完整的cvSetWindowProperty示例
//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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