Creating a UIImage programmatically - Code Error

Question

I wrote this simple extension of UIImage to draw an image starting from a predefined color and a size.

This is the code:

extension UIImage {

    class func image(color:UIColor, size:CGSize)->UIImage {

        UIGraphicsBeginImageContextWithOptions(size, true, 2.0);

        let context = UIGraphicsGetCurrentContext()
        let rect = CGRectMake(0, 0, size.width, size.height)

        color.set()

        CGContextFillRect(context, rect)
        var image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return image
    }
}

If I launch this code in the ViewDidLoad method of a controller I get this error

Oct 31 16:48:02 iPhone Budjet_v2[3387] <Error>: CGContextSetFillColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Oct 31 16:48:02 iPhone Budjet_v2[3387] <Error>: CGContextSetStrokeColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Oct 31 16:48:02 iPhone Budjet_v2[3387] <Error>: CGContextFillRects: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
fatal error: unexpectedly found nil while unwrapping an Optional value

I can't understand what's wrong with my code.

Your code as posted works fine in a test project. The error is elsewhere. — Aaron Brager
– Aaron Brager, Commented Oct 31, 2014 at 16:48
Vague thought: maybe there is no CGContext in existence during viewDidLoad? I'm curious what would happen if you tried it from viewDidAppear; maybe there's no CGContext prior to something actually being drawn. — Anna Dickinson
– Anna Dickinson, Commented Oct 31, 2014 at 21:33

Community · Accepted Answer · 2017-05-23 12:06:08Z

1

This appears to be a bug that was introduced in iOS 7. There is a complete list of the methods that created this error listed in the answer here.

The suggested course of action from this question was to add a symbolic breakpoint to CGPostError to analyze the stack when this error happens in order to determine what is triggering this error.

This error can be triggered by a number of situation and it is impossible to determine which of these scenarios is triggering the error without further research.

Good luck!

edited May 23, 2017 at 12:06

CommunityBot

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answered Oct 31, 2014 at 16:20

Janie Larson

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Jef · Accepted Answer · 2014-10-31 21:32:01Z

1

    if (!(CGSizeEqualToSize(size, CGSizeZero))){

    // your drawing code....

    }else{


return nil;

}

(This ObjC obviously, apologies, I'm not yet an accomplished swift-slinger.... I suspect your problem is a context of size (0,0)

answered Oct 31, 2014 at 21:32

Jef

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