Null Graphics Context

Question

Here is a code excerpt I am using:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^
{

    UIGraphicsBeginImageContextWithOptions(irect.size, YES, 0.0 );
    CGContextRef context = UIGraphicsGetCurrentContext();
    if (context == 0)
        NSLog (@"Null Graphics Context") ;
    else
        NSLog (@"OK") ;

    . . . .
    // Various drawing functions

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
  }) ;

I am finding that every other call to UIGraphicsGetCurrentContext is returning NULL. I get this message on the console.

CGContextRestoreGState: 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.

What would cause UIGraphicsGetCurrentContext to return an invalid graphic context?

There is not enough info in your question. Have you checked out this one post? http://stackoverflow.com/questions/12424690/uigraphicsgetcurrentcontext-seems-to-return-nil — Anthony Kong, Apr 07 '14 at 22:38

score 16 · Accepted Answer · edited Jan 25 '17 at 16:33

16

As suggested by the comment, the answer is that the CGRect passed to UIGraphicsBeginImageContextWithOptions has zero area. That apparently cases it to fail to create a graphics context.

edited Jan 25 '17 at 16:33

spassas

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answered Apr 07 '14 at 22:45

user3344003

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I had the same issue and this was the answer, check if the width AND the height are not 0. – MLBDG May 07 '17 at 18:26

Null Graphics Context

1 Answers1