Question

I need to use an image programmatically made during runtime as a texture but am unsure how to go from one point to another. The image made is with UIGraphicsBeginImageContextwithOptions(), and below is my current code to load a texture from an image in my project:

-(void)loadTextures:(NSString*) filename textureIdentifier:(int) textureNumber {

    //enable textures.
    glEnable(GL_TEXTURE_2D);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_FASTEST);
    glEnable(GL_BLEND); 
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    // Bind the number of textures we need.
    glGenTextures(1, &texture[textureNumber]);
    glBindTexture(GL_TEXTURE_2D, texture[textureNumber]); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D,GL_GENERATE_MIPMAP,GL_TRUE);    
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE);


    NSString *path = [[NSBundle mainBundle] pathForResource:filename 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 );

    // Flip the Y-axis
    CGContextTranslateCTM (context, 0, height);
    CGContextScaleCTM (context, 1.0, -1.0);

    CGColorSpaceRelease( colorSpace );
    CGContextClearRect( context, CGRectMake( 0, 0, width, height ) );
    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);
}

Answer 1

Easy. Remove these lines from the texture loader code and replace them with your Core graphics drawing code:

NSString *path = [[NSBundle mainBundle] pathForResource:filename ofType:@"png"];
NSData *texData = [[NSData alloc] initWithContentsOfFile:path];

Now replace this line:

UIImage *image = [[UIImage alloc] initWithData:texData];

with:

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();