How to optimise core-graphics manipulations into that method ?

I have profiled my app and it spends most of its time in this class method I wrote to combine two UIImages together:

+ (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {开发者_运维问答  

    // Check if UIGraphicsBeginImageContextWithOptions is supported as this can create alphaless contexts and is faster
    if (UIGraphicsBeginImageContextWithOptions != NULL) {
        UIGraphicsBeginImageContextWithOptions(image1.size, YES, 0.0);
    }
    else{

        UIGraphicsBeginImageContext(image1.size);  
    }
    // Draw image1  
    [image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];  

    // Draw image2  
    [image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];  

    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();  

    UIGraphicsEndImageContext();  

    return resultingImage;  
}

Any gurus out there that can suggest ways of optimising this method? Or is it a case of running it in another thread and/or trying not to call it in the first place unless it is absolutely necessary?

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When you say "most of its time", that's ambiguous of course, because it could include callees or not, and it could be CPU time or wall-clock time.

In any case, you want line-level information. What I do is just pause it a few times and examine the call stack. Statements that are responsible for significant time appear preferentially on the stack. If I want it to go faster, I need to find such a line of code that I can avoid executing.