CODEWITHSUNDEEP
iosswiftuiscrollviewuiimageview
Thor
Thor

Reputation: 10038

calculating zoomScaleForHeight using scrollView and imageView's bounds.height property

I'm currently learning the coordinate system in ios and have encountered the following code

let zoomScaleForHeight = scrollView.bounds.height / imageView.bounds.height
let zoomScaleForWidth = scrollView.bounds.width / imageView.bounds.width

scrollView.minimumZoomScale = min(zoomScaleForHeight, zoomScaleForWidth)

imageView is a subview of scrollView.

I'm not exactly sure what is it calculating and how it is calculated. Could someone please clarify the logic behind those three lines of code?

Upvotes: 1

Views: 87

Answers (1)

Christoph
Christoph

Reputation: 722

The minimumZoomScale represents the factor of which the image needs to be resized to in order to perfectly fit the screen without cropping any edges. Here is an image that represents the scenario: Scaling the image

The scale is calculated by dividing the width/height of the UIScrollView by the width/height of the UIImageView. If we would now multiply the width of the UIImageView with its scale factor, we would get the same width as the UIScrollView, which is pretty much what we want to accomplish. The same counts for height.

The reason the min()function is needed is demonstrated by this image: Wrong Scale

In this example, only the scale for the height is applied, the scale for width is not taken into account. By doing that the image fits perfectly in height but not in width. Therefore, both scales have to be calculated and the smaller one is to be used in order the fit the image without cropping the edges.

Upvotes: 3

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