设置openGL窗口的背景图像

Question

我想通过在正交投影矩阵上创建一个四边形并向其中添加纹理来设置我的openGL窗口的背景图像。我也在我的应用程序中使用GLUT工具包。

但是我有几个问题。下面是说明问题的屏幕截图：尽管纹理大小设置为与四边形相同，但图像是灰度，并且它在x和y上重复。

这就是我想实现：

而这正是我得到：

代码渲染和加载纹理看起来是这样的：

void orthogonalStart (void) { 
    glMatrixMode(GL_PROJECTION); 
    glPushMatrix(); 
    glLoadIdentity(); 
    gluOrtho2D(0, w1, 0, h1); 
    glScalef(1, -1, 1); 
    glTranslatef(0, -h1, 0); 
    glMatrixMode(GL_MODELVIEW); 
} 

void orthogonalEnd (void) { 
    glMatrixMode(GL_PROJECTION); 
    glPopMatrix(); 
    glMatrixMode(GL_MODELVIEW); 
} 

GLuint LoadTexture(const char * filename, int width, int height) 
{ 
    GLuint texture; 
    unsigned char * data; 
    FILE * file; 

    //The following code will read in our RAW file 
    file = fopen(filename, "rb"); 
    if (file == NULL) return 0; 
    data = (unsigned char *)malloc(width * height * 3); 
    fread(data, width * height * 3, 1, file); 
    fclose(file); 

    glGenTextures(1, &texture); 
    glBindTexture(GL_TEXTURE_2D, texture); 
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); 


    //even better quality, but this will do for now. 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_LINEAR); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_LINEAR); 


    //to the edge of our shape. 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); 

    //Generate the texture 
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0,GL_RGB, GL_UNSIGNED_BYTE, data); 
    free(data); //free the texture 
    return texture; //return whether it was successful 
} 

void FreeTexture(GLuint texture) 
{ 
    glDeleteTextures(1, &texture); 
} 

void background (void) { 
    glBindTexture(GL_TEXTURE_2D, texture); 

    orthogonalStart(); 

    glBegin(GL_QUADS); 
     glTexCoord2d(0.0,0.0); glVertex2f(0, 0); 
     glTexCoord2d(1.0,0.0); glVertex2f(1024, 0); 
     glTexCoord2d(1.0,1.0); glVertex2f(1024, 1024); 
     glTexCoord2d(0.0,1.0); glVertex2f(0, 1024); 
     glEnd(); 

    orthogonalEnd(); 
} 

void display (void) { 
    glClearColor (1.0,0.0,0.0,1.0); 
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glLoadIdentity(); 
    glEnable(GL_TEXTURE_2D); 

    background(); 
    gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0); 

    glutSwapBuffers(); 
} 

要将png纹理转换为原始格式我使用photoshop，所以我认为灰度图像可能是由于转换。

注意：我刚开始学习开放，所以这可能不是最好的方法。请让我知道是否有更好的方法

编辑：图像上有留在一个地方，而不是rescalse

Answer 1

我倒是avoid doing anything other than a glFrustum() or glOrtho() call你的投影矩阵。

而且，你的纹理加载设置GL_UNPACK_ALIGNMENT为1，如果你正在做的三分量像素：

#include <GL/glut.h> 

int w1 = 0; 
int h1 = 0; 
void reshape(int w, int h) 
{ 
    w1 = w; 
    h1 = h; 
    glViewport(0, 0, w, h); 
} 


void orthogonalStart() 
{ 
    glMatrixMode(GL_PROJECTION); 
    glPushMatrix(); 
    glLoadIdentity(); 
    gluOrtho2D(-w1/2, w1/2, -h1/2, h1/2); 
    glMatrixMode(GL_MODELVIEW); 
} 

void orthogonalEnd() 
{ 
    glMatrixMode(GL_PROJECTION); 
    glPopMatrix(); 
    glMatrixMode(GL_MODELVIEW); 
} 


GLuint texture = 0; 
void background() 
{ 
    glBindTexture(GL_TEXTURE_2D, texture); 

    orthogonalStart(); 

    // texture width/height 
    const int iw = 500; 
    const int ih = 500; 

    glPushMatrix(); 
    glTranslatef(-iw/2, -ih/2, 0); 
    glBegin(GL_QUADS); 
     glTexCoord2i(0,0); glVertex2i(0, 0); 
     glTexCoord2i(1,0); glVertex2i(iw, 0); 
     glTexCoord2i(1,1); glVertex2i(iw, ih); 
     glTexCoord2i(0,1); glVertex2i(0, ih); 
    glEnd(); 
    glPopMatrix(); 

    orthogonalEnd(); 
} 


void display() 
{ 
    glClearColor (1.0,0.0,0.0,1.0); 
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glLoadIdentity(); 
    glEnable(GL_TEXTURE_2D); 

    background(); 
    gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0); 

    glutSwapBuffers(); 
} 


GLuint LoadTexture() 
{ 
    unsigned char data[] = { 255,0,0, 0,255,0, 0,0,255, 255,255,255 }; 

    glGenTextures(1, &texture); 
    glBindTexture(GL_TEXTURE_2D, texture); 
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1); 
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); 

    //even better quality, but this will do for now. 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_NEAREST); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_NEAREST); 

    //to the edge of our shape. 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); 

    //Generate the texture 
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0,GL_RGB, GL_UNSIGNED_BYTE, data); 
    return texture; //return whether it was successful 
} 


int main(int argc, char **argv) 
{ 
    glutInit(&argc, argv); 
    glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE); 

    glutInitWindowSize(800,600); 
    glutCreateWindow("Aspect Ratio"); 

    glutDisplayFunc(display); 
    glutReshapeFunc(reshape); 
    texture = LoadTexture(); 
    glutMainLoop(); 
    return 0; 
}