How Do I Save What I have Drawn In A CGContext

Question

I have drawn into a CGContext of a UIView.

- (void)drawRect:(CGRect)rect { 
    [self drawInContext:UIGraphicsGetCurrentContext()]  
}

I would like to save what I have drawn to a png file.

Is there a simple solution?

EDIT: Based on suggestions below - here's what I have so far....

-(void)createImage {
    NSString* outFile = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/image.png"];
    DLog(@"creating image file at %@", outFile);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); 
    NSData *imageData = UIImagePNGRepresentation(image);
    [imageData writeToFile:outFile 
                atomically:NO];
}

- (void)drawRect:(CGRect)rect { 
    [self drawInContext:UIGraphicsGetCurrentContext()]; 
    [self createImage];
}

maybe a better thing to ask for is how to create a bitmap context and replay my drawings into that. — sylvanaar, Apr 02 '10 at 18:56

score 6 · Answer 1 · edited Feb 22 '13 at 12:19

6

CGImageRef imgRef = CGBitmapContextCreateImage(context);

UIImage* img = [UIImage imageWithCGImage:imgRef];

CGImageRelease(imgRef);

edited Feb 22 '13 at 12:19

Shawn Chin

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answered Feb 22 '13 at 08:56

Prashanth Rajagopalan

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1

Don't just post code as an answer, try to give it some explanation as to why this will help. – Dutts Feb 22 '13 at 09:19

score 6 · Accepted Answer · answered Apr 02 '10 at 18:57

6

UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); 
NSData *imageData = UIImagePNGRepresentation(image);
[imageData writeToFile:@"image.png"];

answered Apr 02 '10 at 18:57

indragie

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I must be missing something simple. I do this within the drawRect call. Running on the iPhone simulator - i don't see any file created. – sylvanaar Apr 02 '10 at 19:33
You may have to specify the complete path to the Documents directory instead of just image.png. – indragie Apr 02 '10 at 20:59
I updated my example code above - but no file is created in the emulator. Thanks for the help though. – sylvanaar Apr 03 '10 at 04:44

score 1 · Answer 3 · answered Apr 02 '10 at 18:38

1

Call UIGraphicsGetImageFromCurrentImageContext to get an UIImage.
Then call UIImagePNGRepresentation to get an NSData of the UIImage encoded in PNG.
Finally, call -writeToFile:… to save the NSData.

answered Apr 02 '10 at 18:38

kennytm

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score 0 · Answer 4 · answered Jun 09 '19 at 22:15

let imageWidth = inputCGImage.width
let imageHeight = inputCGImage.height

let imageRect = NSRect(
    origin: .zero,
    size: CGSize(width: imageWidth, height: imageHeight)
)

context.draw(inputCGImage, in: imageRect)

let outputImageRef = context.makeImage()!

let paths = NSSearchPathForDirectoriesInDomains(.desktopDirectory, .userDomainMask, true) as [String]

let destinationURL = NSURL(fileURLWithPath: paths.first!).appendingPathComponent("output.png")!

guard let destination = CGImageDestinationCreateWithURL(destinationURL as CFURL, kUTTypePNG, 1, nil) else {
    throw HoleFillingError.CoreGraphicsError
}

CGImageDestinationAddImage(destination, outputImageRef, nil)
CGImageDestinationFinalize(destination)

How Do I Save What I have Drawn In A CGContext

4 Answers4

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