+ (id)spriteWithCGImage:(CGImageRef)image key:(NSString *)key

/* function that draw your shape in a CGContextRef */
 void DrawShape(CGContextRef ctx)
 {
     // draw a simple triangle

     CGContextMoveToPoint(ctx, 50, 100);
     CGContextAddLineToPoint(ctx, 100, 0);
     CGContextAddLineToPoint(ctx, 0, 0);
     CGContextClosePath(ctx);
  }


    void CreateImage(void)
    {
       UIGraphicsBeginImageContext(CGSizeMake(100, 100));

       DrawShape(UIGraphicsGetCurrentContext());

       UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

       UIGraphicsEndImageContext();

       // now you've got an (autorelease) UIImage, that you can use to
       // create your sprite.
       // use image.CGImage if you need a CGImageRef
    }

CGContextRef CreateBitmapContextWithData(int width, int height, void *buffer)
{
    CGContextRef ctx;
    CGColorSpaceRef colorspace;
    size_t bytesPerRow;
    size_t bitsPerComponent;
    size_t numberOfComponents;
    CGImageAlphaInfo alpha;

    bitsPerComponent = 8;
    alpha = kCGImageAlphaPremultipliedLast;

    numberOfComponents = 1;
    colorspace = CGColorSpaceCreateDeviceRGB();

    numberOfComponents += CGColorSpaceGetNumberOfComponents(colorspace);
    bytesPerRow = (width * numberOfComponents);

    ctx = CGBitmapContextCreate(buffer, width, height, bitsPerComponent, bytesPerRow, colorspace, alpha);

    CGColorSpaceRelease(colorspace);

    return ctx;
}

void CreateImageOrGLTexture(void)
{
   // use pow2 width and height to create your own glTexture ...
   void *buffer = calloc(1, 128 * 128 * 4);
   CGContextRef ctx = CreateBitmapContextWithData(128, 128, buffer);

   // draw you shape
   DrawShape(ctx);

   // you can create a CGImageRef with this context
   // CGImageRef image = CGBitmapContextCreateImage(ctx);

   // you can create a gl texture with the current buffer
   // glBindTexture(...)
   // glTexParameteri(...)
   // glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

   CGContextRelease(ctx);
   free(buffer);
}