如何在 mac 中为 openGL 背景窗口使用纹理 .jpg 图像？

Question

我想为 mac 的 openGL 窗口设置背景。背景将采用 jpg 或 png 文件。

这是我的代码..

GLuint texture; //the array for our texture

GLfloat angle = 0.0;

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 ); 
glPixelStorei( GL_UNPACK_ALIGNMENT, 1 );
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ); 

//    // when texture area is small, bilinear filter the closest mipmap
//    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
//                    GL_LINEAR_MIPMAP_NEAREST );
//    // when texture area is large, bilinear filter the original
//    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
//    
//    // the texture wraps over at the edges (repeat)
//    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);



// select modulate to mix texture with color for shading
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );

// when texture area is small, bilinear filter the closest mipmap
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                GL_LINEAR_MIPMAP_NEAREST );
// when texture area is large, bilinear filter the first mipmap
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

//    // the texture wraps over at the edges (repeat)
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );

// build our texture mipmaps
gluBuild2DMipmaps( GL_TEXTURE_2D, 3, width, height,
                  GL_RGB, GL_UNSIGNED_BYTE, data );

free(data);

return texture; //return whether it was successful

}

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

void cube () {
glEnable(GL_TEXTURE_2D);
glBindTexture( GL_TEXTURE_2D, texture ); //bind the texture

glPushMatrix();
glRotatef( angle, 0.0f, 0.0f, 1.0f );
glBegin( GL_QUADS );
glTexCoord2d(0.0,0.0); glVertex2d(-1.0,-1.0);
glTexCoord2d(1.0,0.0); glVertex2d(+1.0,-1.0);
glTexCoord2d(1.0,1.0); glVertex2d(+1.0,+1.0);
glTexCoord2d(0.0,1.0); glVertex2d(-1.0,+1.0);
glEnd();
glPopMatrix();
glutSwapBuffers();
//glutSolidCube(2);
}

void display () {
   glClearColor (0.0,0.0,0.0,1.0);
   glClear (GL_COLOR_BUFFER_BIT);
   glLoadIdentity();
   gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
   texture = LoadTexture( "/Users/macbook/MatrixEngineClientSample/Fighters/Sunset03.jpg", 256, 256  ); //load the texture
   glEnable( GL_TEXTURE_2D ); //enable 2D texturing
//    glEnable(GL_TEXTURE_GEN_S); //enable texture coordinate generation
//    glEnable(GL_TEXTURE_GEN_T);
  cube();
  FreeTexture( texture );
  //glutSwapBuffers();
  //angle ++;
}

void reshape (int w, int h) {
  glViewport (0, 0, (GLsizei)w, (GLsizei)h);
  glMatrixMode (GL_PROJECTION);
  //glLoadIdentity ();
  gluPerspective (50, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
  glMatrixMode (GL_MODELVIEW);
}

int main (int argc, char **argv) {
  glutInit (&argc, argv);
  glutInitDisplayMode (GLUT_DOUBLE);
  glutInitWindowSize (500, 500);
  glutInitWindowPosition (100, 100);
  glutCreateWindow ("A basic OpenGL Window");
  glutDisplayFunc (display);
  glutIdleFunc (display);
  glutReshapeFunc (reshape);
  glutMainLoop ();
  return 0;
}

编辑

我想将此图像视为 openGL 窗口的背景...图像在下方..

但它显示了这个......

Answer 1

我咨询了this Apple guide。

问题是文件被压缩并且有一个标题，并且你的代码甚至使用文件标题的一部分作为图像源。

我会替换这段代码：

//    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 );

有了更类似的东西：

CFURLRef urlRef = (CFURLRef)[NSURL fileURLWithPath:@"/Users/macbook/MatrixEngineClientSample/Fighters/Sunset03.jpg"];
CGImageSourceRef myImageSourceRef = CGImageSourceCreateWithURL(url, NULL);
CGImageRef myImageRef = CGImageSourceCreateImageAtIndex(myImageSourceRef, 0, NULL);
CFDataRef data = CGDataProviderCopyData(CGImageGetDataProvider(myImageRef));
unsigned char *data = CFDataGetBytePtr(data);

您可能需要将 Core Graphics 和 Core Foundation 添加到链接框架列表中。

Answer 2

PNG 和 JPG 图像（与大多数其他图像格式一样）需要某种形式的解压缩/解码，因此从文件中原始加载它们不会产生预期的结果。在读取文件头后，它应该可以处理 bmp 或未压缩的 tga 图像：/。无论如何，这里有一些图像加载库应该可以让加载图像变得容易：

SOIL

DevIL

FreeImage

GLI