processing image - opencv - image

Question

I've got the code (using VS2010, C++, Windows Forms Application) below:
#pragma once
#include <cv.h>
#include <highgui.h>
#ifdef _DEBUG
//debug
#pragma comment(lib,"cv210d.lib")
#pragma comment(lib,"cxcore210d.lib")
#pragma comment(lib,"cvaux210d.lib")
#pragma comment(lib,"highgui210d.lib")
#else
//release
#pragma comment(lib,"cv210.lib")
#pragma comment(lib,"cxcore210.lib")
#pragma comment(lib,"cvaux210.lib")
#pragma comment(lib,"highgui210.lib")
#endif
//Global variables
IplImage* src = NULL;
IplImage* hsv = NULL;
IplImage* dst = NULL;
IplImage* v_plane = NULL;
IplImage* h_plane = NULL;
IplImage* s_plane = NULL;
namespace HW4 {
using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;
/// <summary>
/// Summary for Form1
/// </summary>
public ref class Form1 : public System::Windows::Forms::Form
{
public:
Form1(void)
{
InitializeComponent();
//
//TODO: Add the constructor code here
//
}
protected:
/// <summary>
/// Clean up any resources being used.
/// </summary>
~Form1()
{
if (components)
{
delete components;
}
}
private: System::Windows::Forms::PictureBox^ pictureBox1;
protected:
private: System::Windows::Forms::PictureBox^ pictureBox2;
private: System::Windows::Forms::Button^ ExitButton;
private:
/// <summary>
/// Required designer variable.
/// </summary>
System::ComponentModel::Container ^components;
#pragma region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
void InitializeComponent(void)
{
this->pictureBox1 = (gcnew System::Windows::Forms::PictureBox());
this->pictureBox2 = (gcnew System::Windows::Forms::PictureBox());
this->ExitButton = (gcnew System::Windows::Forms::Button());
(cli::safe_cast<System::ComponentModel::ISupportInitialize^ >(this->pictureBox1))->BeginInit();
(cli::safe_cast<System::ComponentModel::ISupportInitialize^ >(this->pictureBox2))->BeginInit();
this->SuspendLayout();
//
// pictureBox1
//
this->pictureBox1->Location = System::Drawing::Point(12, 49);
this->pictureBox1->Name = L"pictureBox1";
this->pictureBox1->Size = System::Drawing::Size(255, 212);
this->pictureBox1->SizeMode = System::Windows::Forms::PictureBoxSizeMode::StretchImage;
this->pictureBox1->TabIndex = 0;
this->pictureBox1->TabStop = false;
//
// pictureBox2
//
this->pictureBox2->Location = System::Drawing::Point(354, 49);
this->pictureBox2->Name = L"pictureBox2";
this->pictureBox2->Size = System::Drawing::Size(255, 212);
this->pictureBox2->SizeMode = System::Windows::Forms::PictureBoxSizeMode::StretchImage;
this->pictureBox2->TabIndex = 1;
this->pictureBox2->TabStop = false;
//
// ExitButton
//
this->ExitButton->Location = System::Drawing::Point(272, 278);
this->ExitButton->Name = L"ExitButton";
this->ExitButton->Size = System::Drawing::Size(64, 31);
this->ExitButton->TabIndex = 2;
this->ExitButton->Text = L"Exit";
this->ExitButton->UseVisualStyleBackColor = true;
this->ExitButton->Click += gcnew System::EventHandler(this, &Form1::ExitButton_Click);
//
// Form1
//
this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
this->ClientSize = System::Drawing::Size(635, 333);
this->Controls->Add(this->ExitButton);
this->Controls->Add(this->pictureBox2);
this->Controls->Add(this->pictureBox1);
this->Name = L"Form1";
this->Text = L"Form1";
this->Load += gcnew System::EventHandler(this, &Form1::Form1_Load);
(cli::safe_cast<System::ComponentModel::ISupportInitialize^ >(this->pictureBox1))->EndInit();
(cli::safe_cast<System::ComponentModel::ISupportInitialize^ >(this->pictureBox2))->EndInit();
this->ResumeLayout(false);
}
#pragma endregion
private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) {
src = cvLoadImage("D:\\Pictures\\hungry.jpg");
dst = cvCreateImage(cvGetSize(src),8,3);
hsv = cvCreateImage(cvGetSize(src),8,3);
h_plane = cvCreateImage(cvGetSize(src),8,1);
s_plane = cvCreateImage(cvGetSize(src),8,1);
v_plane = cvCreateImage(cvGetSize(src),8,1);
cvCvtColor(src,hsv,CV_BGR2HSV);
cvSplit(hsv,h_plane,s_plane,v_plane,0);
cvEqualizeHist(v_plane,v_plane);
cvMerge(h_plane,s_plane,v_plane,0,hsv);
cvCvtColor(hsv,dst,CV_HSV2BGR);
//Before you debug, choose SizeMode property of PictureBoxs = StretchImage.
pictureBox1->Image = gcnew //replacement of cvShowImage
System::Drawing::Bitmap(src->width,src->height,src->widthStep,
System::Drawing::Imaging::PixelFormat::Format24bppRgb,(System::IntPtr) src->imageData);
pictureBox1->Refresh();
pictureBox2->Image = gcnew //replacement of cvShowImage
System::Drawing::Bitmap(dst->width,dst->height,dst->widthStep,
System::Drawing::Imaging::PixelFormat::Format24bppRgb,(System::IntPtr) dst->imageData);
pictureBox2->Refresh();
/*cvReleaseImage(&src);
cvReleaseImage(&hsv);
cvReleaseImage(&dst);
cvReleaseImage(&h_plane);
cvReleaseImage(&s_plane);
cvReleaseImage(&v_plane);*/
}
private: System::Void ExitButton_Click(System::Object^ sender, System::EventArgs^ e) {
cvReleaseImage(&src);
cvReleaseImage(&hsv);
cvReleaseImage(&dst);
cvReleaseImage(&h_plane);
cvReleaseImage(&s_plane);
cvReleaseImage(&v_plane);
this->Close();
}
};
}
Consider the part of code:
cvReleaseImage(&src);
cvReleaseImage(&hsv);
cvReleaseImage(&dst);
cvReleaseImage(&h_plane);
cvReleaseImage(&s_plane);
cvReleaseImage(&v_plane);
if i put this part at the end of the Form1_Load, there'll be an error as the following picture:
However, if i put this part in the ExitButton_Click function, it's ok!
i don't know why ? hope someone can give me an explaination ! thanks for your help !^~^

Answer 1

In the following line you are using opencv image buffers and if you fee these buffers in the end of form load function, .net engine could not load image anymore
But if you free the buffer in form exit, it won't care ...
pictureBox1->Image = gcnew ...

Answer 2

The Form-Load event in .Net can be used to allocate resources before the form is loaded and rendered. By freeing the image buffer at the end of the load, you remove the image resource that the form needs to display. Just imagine that there is some internal method that calls your Load() method and then it calls an internal Display() method, which uses data from the Load() method. If you load the data and then release it before the "Display()" method is called, you are freeing memory that is required in the Display() method.
As Roozbeh said, if you put it in the exit, the form is not trying to display anything so it doesn't need that image resource (from the buffer). The exit method is naturally a good place to deallocate things.