Question

I’m creating an iPhone game and I need to load an image from a PNG file into OpenGL (and bind it as a texture). I’m using function glTexImage2D to achieve this goal.

I know how to load an image into OpenGL using UIImage (by converting it into CGImage and afterwards drawing into a context).

How can I call my Objective-C code from within C++ code (I’m coding in .mm file)?

Here’s the code I’m using and that would work in Objective-C:

NSString *path = [[NSBundle mainBundle] pathForResource:@"texture" ofType:@"png"];
    NSData *texData = [[NSData alloc] initWithContentsOfFile:path];
    UIImage *image = [[UIImage alloc] initWithData:texData];
    if (image == nil)
        NSLog(@"Do real error checking here");

    GLuint width = CGImageGetWidth(image.CGImage);
    GLuint height = CGImageGetHeight(image.CGImage);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    void *imageData = malloc( height * width * 4 );
    CGContextRef context = CGBitmapContextCreate( imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big );
    CGColorSpaceRelease( colorSpace );
    CGContextClearRect( context, CGRectMake( 0, 0, width, height ) );
    CGContextTranslateCTM( context, 0, 0 );
    CGContextDrawImage( context, CGRectMake( 0, 0, width, height ), image.CGImage );

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);

    CGContextRelease(context);

    free(imageData);
    [image release];
    [texData release];

Is there a way to call those UI and Core Graphics functions from C++ code? What files do I have to include?

Thank you in advance.

Answer 1

Solved the problem. Had to find manually and add the Core Graphics framework.