Setting UIImageView image affects layout constraints

Question

I am creation a simple UIImageView with the following constraints:

self.view.addConstraint(imageView.topAnchor.constraint(equalTo: contentLayoutGuide.topAnchor))
self.view.addConstraint(imageView.centerXAnchor.constraint(equalTo: contentLayoutGuide.centerXAnchor))
self.view.addConstraint(imageView.heightAnchor.constraint(equalTo: contentLayoutGuide.heightAnchor))
self.view.addConstraint(imageView.widthAnchor.constraint(equalTo: contentLayoutGuide.heightAnchor))

The important one is the last one, which sets the width equal to the height of the image view and the height of the image view is being defined by top and bottom anchor.

Now this looks perfectly fine (see image below)

However when setting imageView.image the image is all over the screen and way too big. This debugging process fixes it:

po for cn in self.imageView!.constraints { cn.isActive = false }
po CATransaction.flush()

This makes the image fit inside the imageView as it is intended but up until this point, the imageView is messed up.

What is interesting, before setting the image, the imageView itself does not have any constraints and then setting the image creates those two:

- 0 : <NSContentSizeLayoutConstraint:0x6040002b2120 UIImageView:0x7fa98f757b90.width == 488 Hug:250 CompressionResistance:750   (active)>
- 1 : <NSContentSizeLayoutConstraint:0x6040002b2180 UIImageView:0x7fa98f757b90.height == 487 Hug:250 CompressionResistance:750   (active)>

Those constraints seem to break it, because disabling them fixes the problem. They are only added when setting an image

Did you set translatesAutoresizingMaskIntoConstraints to false on the imageView? — Paolo
– Paolo, Commented Oct 10, 2017 at 20:48
yes, of course. otherwise the constraints would break by default — Janosch Hübner
– Janosch Hübner, Commented Oct 10, 2017 at 20:53
Did you set the content mode of the image view to aspect fit? — Wes
– Wes, Commented Oct 10, 2017 at 23:38

regina_fallangi · Accepted Answer · 2020-04-17 18:47:14Z

16

Try to lower the content compression/hugging. I think (correct me if I am wrong) the UIImageView has by default a higher compression/hugging resistance than a UIView (251 to 250). You could try the code below:

someImage.setContentHuggingPriority(UILayoutPriority(rawValue: 249), for: .horizontal)
someImage.setContentCompressionResistancePriority(UILayoutPriority(rawValue: 249), for: .horizontal)
someImage.setContentHuggingPriority(UILayoutPriority(rawValue: 249), for: .vertical)
someImage.setContentCompressionResistancePriority(UILayoutPriority(rawValue: 249), for: .vertical)

edited Apr 17, 2020 at 18:47

regina_fallangi

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answered Oct 10, 2017 at 21:14

J. Doe

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2 Comments

Janosch Hübner Over a year ago

using .defaultLow (250) also works, by default it seems to be .defaultHigh, which (750) which causes this bug

Roman Over a year ago

Image doesn't have setContentHuggingPriority and setContentHuggingPriority. ImageView does. I have the same issue but in my case the solution doesn't work.

Vanita L. · Accepted Answer · 2017-10-11 07:23:48Z

3

try to set clipsToBounds property to true for UIImageView and check, since for few contentMode options the image goes out of bound of image view if the bounds are not enough to fill the content.

answered Oct 11, 2017 at 7:23

Vanita L.

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Comments

Chambo7 · Accepted Answer · 2017-10-10 21:10:25Z

2

Is your UIImageView masking to bounds? If the image is bigger than the UIImageView then by default it will extend past the bounds

imageView.layer.masksToBounds = true

Alternatively have you tried changing the content fit of the UIImageView to Aspect Fit for example?

answered Oct 10, 2017 at 21:10

Chambo7

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1 Comment

pjl91 Over a year ago

For my case, this worked. I have a tableviewcell views with autolayout constraints, wherein the UIImageView is placed to the left, and placed side by side to the right of UILabels. But somehow my UILabels overlap the UIImageView by some weird margins. This workaround has solved my issue.

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