opengl学习笔记（四）:openCV读入图片，openGL实现纹理贴图

在opengl中实现三维物体的纹理贴图的第一步就是要读入图片，然后指定该图片为纹理图片。

首先利用opencv的cvLoadImage函数把图像读入到内存中

img = cvLoadImage("../shanghai.bmp", 1);   //读入彩色图

然后利用下面代码在内存中开辟一个跟读入图片大小相同的内存空间：

#include <iostream>
#include <GL/gl.h>
#include <GL/glu.h>
#include <opencv2/opencv.hpp>

using namespace cv;
using namespace std;

/*
Mat img = imread("../shanghai.bmp");

int width = img.cols;
int height = img.cols;

GLubyte* pixels;

GLuint load_texture(cv::Mat& image)
{
    int width = image.cols;
    int height = image.cols;
    //OpenGL纹理用整型数表示
    GLuint texture_ID;

    //获取图像指针
    int pixellength = width*height*3;
    pixels = new GLubyte[pixellength];
    memcpy(pixels, image.data, pixellength * sizeof(unsigned char));

    //将texture_ID设置为2D纹理信息
    glGenTextures(1, &texture_ID);
    glBindTexture(GL_TEXTURE_2D, texture_ID);
    //纹理放大缩小使用线性插值
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, pixels);

    free(pixels);
    return texture_ID;
}

void draw()
{
    glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    drawCameraFrame();
    glFlush();
}

void drawCameraFrame()
{
    GLuint image = load_texture();
    if (!m_isTextureInitialized)
    {
        glGenTextures(1, &m_backgroundTextureId);
        glBindTexture(GL_TEXTURE_2D, m_backgroundTextureId);

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        m_isTextureInitialized = true;
    }

    int w = m_backgroundTextureId.cols;
    int h = m_backgroundTextureId.rows;

    glPixelStorei(GL_PACK_ALIGNMENT, 1);
    glBindTexture(GL_TEXTURE_2D, m_backgroundTextureId);

    if (m_backgroundImage.channels() == 3)
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, m_backgroundImage.data);
    else if(m_backgroundImage.channels() == 4)
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_BGRA_EXT, GL_UNSIGNED_BYTE, m_backgroundImage.data);
    else if (m_backgroundImage.channels()==1)
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, m_backgroundImage.data);

    const GLfloat bgTextureVertices[] = { 0, 0, w, 0, 0, h, w, h };
    const GLfloat bgTextureCoords[]   = { 1, 0, 1, 1, 0, 0, 0, 1 };
    const GLfloat proj[]              = { 0, -2.f/w, 0, 0, -2.f/h, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1 };

    glMatrixMode(GL_PROJECTION);
    glLoadMatrixf(proj);

    glMatrixMode(GL_MODEVIEW);
    glLoadIdentity();

    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, m_backgroundTextureId);

    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    glVertexPointer(2, GL_FLOAT, 0, bgTextureVertices);
    glTexCoordPointer(2, GL_FLOAT, 0, bgTextureCoords);

    glColor4f(1,1,1,1);
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisable(GL_TEXTURE_2D);
}

void processVideo()
{
    cv::Mat currentFrame;
    capture >> currentFrame;

    // Check the capture succeeded:
    if (currentFrame.empty())
    {
        std::cout << "Cannot open video capture device" << std::endl;
        return;
    }

    cv::Size frameSize(currentFrame.cols, currentFrame.rows);
}

bool processFrame(const cv::Mat& cameraFrame)
{
    // Clone image used for background (we will draw overlay on it)
    cv::Mat img = cameraFrame.clone();

    // Set a new camera frame:
    drawingCtx.updateBackground(img);

    // Request redraw of the window:
    drawingCtx.updateWindow();


}

int main( int argc, char** argv)
{
    cv::VideoCapture capture = cv::VideoCapture(1);
    cv::namedWindow(windowName, cv::WINDOW_OPENGL);
    cv::resizeWindow(windowName, frameSize.width, frameSize.height);
    cv::setOpenGlContext(windowName);
    cv::setOpenGlDrawCallback(windowName, draw, NULL);
    cv::updateWindow(windowName);

}
*/

Mat m_backgroundImage = imread("../shanghai.bmp");
GLuint m_backgroundTextureId;

void drawCameraFrame()
{
    glGenTextures(1, &m_backgroundTextureId);
    glBindTexture(GL_TEXTURE_2D, m_backgroundTextureId);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); 


    int w = m_backgroundImage.cols;
    int h = m_backgroundImage.rows;

    glPixelStorei(GL_PACK_ALIGNMENT, 1);
    glBindTexture(GL_TEXTURE_2D, m_backgroundTextureId);

  // Upload new texture data:

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, m_backgroundImage.data);
  
    //glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_BGRA_EXT, GL_UNSIGNED_BYTE, m_backgroundImage.data);
  
    //glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, m_backgroundImage.data);
    
    const GLfloat bgTextureVertices[] = { 0, 0, w, 0, 0, h, w, h };
    const GLfloat bgTextureCoords[]   = { 1, 0, 1, 1, 0, 0, 0, 1 };
    const GLfloat proj[]              = { 0, -2.f/w, 0, 0, -2.f/h, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1 };

    glMatrixMode(GL_PROJECTION);
    glLoadMatrixf(proj);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, m_backgroundTextureId);

    // Update attribute values.
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    glVertexPointer(2, GL_FLOAT, 0, bgTextureVertices);
    glTexCoordPointer(2, GL_FLOAT, 0, bgTextureCoords);

    glColor4f(1,1,1,1);
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisable(GL_TEXTURE_2D);

}

void draw(void* param)
{
    glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    drawCameraFrame(); 
    glFlush();
}

int main ( int argc, char** argv )
{
    cv::namedWindow("windowName", cv::WINDOW_OPENGL);

    cv::resizeWindow("windowName", m_backgroundImage.cols, m_backgroundImage.rows);

    cv::setOpenGlContext("windowName");

    cv::setOpenGlDrawCallback("windowName", draw, NULL);

    updateWindow("windowName");
    waitKey(0);
    return 0;
}

/*

#include <GL/glut.h>
#include <GL/gl.h>
#include <opencv2/cv.h>
#include <opencv2/highgui/highgui.hpp>

GLuint texture; //纹理图
IplImage *img;
unsigned char* textureImage;

void makeTextureImg(IplImage *image)
{
    int width = image->width;
    int height = image->height;
    CvScalar s;

    //读入彩色图
    textureImage = new unsigned char[width * height * 3];
    for (int i = 0; i < height; i++ )
        for (int j = 0; j < width; j++)
        {
            s = cvGet2D(image, i, j);
            textureImage[i * 3 * width + 3 * j] = s.val[0];
            textureImage[i * 3 * width + 3 * j + 1] = s.val[1];
            textureImage[i * 3 * width + 3 * j + 2] = s.val[2];
        }     

}

int loadTexture(IplImage* image, GLuint* text)
{
    if (image==NULL) return -1;
    glGenTextures(1, text);
    glBindTexture(GL_TEXTURE_2D, *text);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);

    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image->width, image->height, 0, GL_RGB, GL_UNSIGNED_BYTE, image->data);

    return 0;

}

void display()
{
    glClearColor (0.0,0.0,0.0,1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}

int main(int argc, char** argv)
{
    glutInit (&argc, argv);
    glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE);
    glutInitWindowSize (500, 500);
}
*/

程序运行结果如下：

参考博客：

https://blog.csdn.net/learn_sunzhuli/article/details/46642379

http://blog.sina.com.cn/s/blog_8d8425f30100yoi4.html

https://blog.csdn.net/u013898698/article/details/77164775

https://blog.csdn.net/wan_exe/article/details/70943020

 代码下载：github