Draw on UIImageView without replacing its original image iOS

Question

This code make changes to the imageview, but it replaces its original image. I need to edit on the original image not to replace it.

- (void)drawShapes {
    //NSLog(@"In drawShapes!");

    UIGraphicsBeginImageContext(self.planView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

    for(myShape *i in _collection) {
        [self drawShapesSubroutine:i contextRef:context];
        if(i.selected == true) {
            CGContextSetLineWidth(context, 1.0f);
            CGContextSetStrokeColorWithColor(context, [[UIColor darkGrayColor] CGColor]);
            float num[] = {6.0, 6.0};
            CGContextSetLineDash(context, 0.0, num, 2);

            CGRect rectangle;
            [self drawShapeSelector:i selectorRect: &rectangle];
            CGContextAddRect(context, rectangle);
            CGContextStrokePath(context);


            //tapped = true;
        }
    }

    if(!skipDrawingCurrentShape && (selectedIndex == -1)) {
        [self drawShapesSubroutine:_currentShape contextRef:context];
    }
    self.planView.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}

When I remove this line:

self.planView.image = UIGraphicsGetImageFromCurrentImageContext();

The image doesn't disappear but also doesn't draw. I need to draw without removing the original photo.

you cant do imagview.image because, it will replace the old image with new one. If you are planning to draw something new on the image view, try to add sublayer on the imageview — Teja Nandamuri, Oct 19 '15 at 14:38
UIGraphicsGetImageFromCurrentImageContext() this returns an image it refusers to do this : [self.planView.layer addSublayer: UIGraphicsGetImageFromCurrentImageContext()]; — Mostafa Sultan, Oct 19 '15 at 14:43
which image this ? UIGraphicsGetImageFromCurrentImageContext() or this self.planView.image — Mostafa Sultan, Oct 19 '15 at 14:52
you should convert UIGraphicsGetImageFromCurrentImageContext() into UIGraphicsGetImageFromCurrentImageContext().CGImage; — Teja Nandamuri, Oct 19 '15 at 14:53
[self.planView.layer addSublayer: UIGraphicsGetImageFromCurrentImageContext().CGImage]; this crashes — Mostafa Sultan, Oct 19 '15 at 14:54
you need to create a CALayer and add your CGI image to the layer.contents and use that layer as sub layer — Teja Nandamuri, Oct 19 '15 at 15:02
see this for example http://stackoverflow.com/questions/13272512/add-uiimage-in-calayer — Teja Nandamuri, Oct 19 '15 at 15:02

score 6 · Answer 1 · answered Oct 19 '15 at 15:06

6

You cant do imagview.image because, it will replace the old image with new one. If you are planning to draw something new on the image view, try to add sublayer on the imageview.

convert your image into cgiimage and add it to layer.you should convert UIGraphicsGetImageFromCurrentImageContext() into UIGraphicsGetImageFromCurrentImageContext().CGImage

you need to create a CALayer and add your CGI image to the layer.contents and use that layer as sub layer

CALayer *layer = [CALayer layer];
layer.contents = (id)UIGraphicsGetImageFromCurrentImageContext().CGImage;

and do this:

[self.imageView.layer addSublayer:layer];

answered Oct 19 '15 at 15:06

Teja Nandamuri

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for my task i won't make addsublayer except for the first time , and keep editing that layer – Mostafa Sultan Oct 19 '15 at 15:10
the CALayer *layer = [CALayer layer]; line gives linker error – Mostafa Sultan Oct 19 '15 at 15:28
1

maybe you should add QuartzCore framework to your project. – Teja Nandamuri Oct 19 '15 at 15:30
Undefined symbols for architecture i386: "_OBJC_CLASS_$_CALayer", referenced from: objc-class-ref in ECS189DrawingViewController.o ld: symbol(s) not found for architecture i386 clang: error: linker command failed with exit code 1 (use -v to see invocation) – Mostafa Sultan Oct 19 '15 at 15:35
did u try adding quartzcore ? – Teja Nandamuri Oct 19 '15 at 15:37
i have included it and nothing changed i don't know why here is the link to that simple project , the class named ECS189DrawingViewController.m https://www.dropbox.com/home?preview=DrawingApp-master.zip – Mostafa Sultan Oct 20 '15 at 10:47
1

i will look into it. I couldnt see the file at the link you provided – Teja Nandamuri Oct 20 '15 at 12:25

Draw on UIImageView without replacing its original image iOS

1 Answers1