将 jpg 图像加载为纹理 - freeimage, opengl

Question

我尝试使用 FreeImage 库加载 jpg 图像。我使用了这段代码，但结果只是白色窗口。我想使用此图像作为背景，然后加载目标文件。

这是我使用的代码：

#include <windows.h>
#include <GL/glut.h>
#include <iostream>
#include <FreeImage.h>

FIBITMAP  *loadImage(const char *filename)
{
    FIBITMAP *dib1 = NULL;
    FREE_IMAGE_FORMAT fif = FreeImage_GetFIFFromFilename(filename);

    dib1 = FreeImage_Load(fif, filename, JPEG_DEFAULT);
    if (!dib1)
    {
       std::cerr << "Erreur ouverture d\'image" << std::endl;
       exit (0);

    } 
    std::cerr << "Success" << std::endl;
    return dib1;
}

GLuint loadTexture (FIBITMAP  * dib1)
{
    GLuint tex_id = 0;
    int x, y;
    int height, width;

    RGBQUAD rgbquad;
    FREE_IMAGE_TYPE type;
    BITMAPINFOHEADER *header;

    type = FreeImage_GetImageType(dib1);
    height = FreeImage_GetHeight(dib1);
    width = FreeImage_GetWidth(dib1);

    header = FreeImage_GetInfoHeader(dib1);
    int scanLineWidh = ((3*width)%4 == 0) ? 3*width : ((3*width)/4)*4+4;
    unsigned char * texels= (GLubyte*)calloc(height*scanLineWidh, sizeof(GLubyte));
    for (x=0 ; x<width ; x++)
        for (y=0 ; y<height; y++)
        {  
          FreeImage_GetPixelColor(dib1,x,y,&rgbquad);

          texels[(y*scanLineWidh+3*x)]=((GLubyte*)&rgbquad)[2];
          texels[(y*scanLineWidh+3*x)+1]=((GLubyte*)&rgbquad)[1];
          texels[(y*scanLineWidh+3*x)+2]=((GLubyte*)&rgbquad)[0];
         }

        glGenTextures (1, &tex_id);
        glBindTexture (GL_TEXTURE_2D, tex_id);

        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_RGB,
            GL_UNSIGNED_BYTE, texels);

      free(texels);
      return tex_id;
}
void display(void)
{  
    glClearColor (0.0,0.0,0.0,1.0); 
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glutSwapBuffers(); //swap the buffers

}


int main(int argc, char **argv) {

 FIBITMAP  *dib1 = loadImage("planina.jpg");

    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
    glutInitWindowSize(800,450);
    glutInitWindowPosition(20,20);
    glutCreateWindow("Loader");
    //glutReshapeFunc(reshape);
    //glutDisplayFunc(display);
    loadTexture(dib1);
    FreeImage_Unload(dib1);
    glutMainLoop();
    return 0;
}

我做错了什么？

Answer 1

这是你的显示函数：

void display(void)
{  
    glClearColor (0.0,0.0,0.0,1.0); 
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glutSwapBuffers(); //swap the buffers

}

显而易见的是，它唯一能做的就是

1. 设置清晰的颜色
2. 清空窗口
3. 加载单位矩阵
4. 显示结果

缺少的是任何一种实际绘制的东西。您必须使用应用于纹理的纹理绘制一些三角形或四边形，才能以某种方式实际显示出来。