StackOverflow2013

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plurals

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7761909
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2011-10-14T00:25:03.603
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2011-10-14T00:25:03.603
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Body
I disagree with one of the comments above saying that you should never multiply the center's coordinates by some factor. Say that you are currently displaying an entire 400x400px image or PDF file in a 100x100 scroll view and want to allow the users to double the size of the content until it's 1:1. If you double tap at point (75,75), you expect the zoomed-in rectangle to have origin 100,100 and size 100x100 within the new 200x200 content view. So the original tapping point (75,75) is now (150,150) in the new 200x200 space. Now, after zoom action #1 has completed, if you again double tap at (75,75) inside the new 100x100 rectangle (which is the bottom-right square of the larger 200x200 rectangle), you expect the user to be shown the bottom-right 100x100 square of the larger image, which would now become zoomed to 400x400 pixels. In order to calculate the origin of this latest 100x100 rectangle within the larger 400x400 rectangle, you would need to consider the scale and current content offset (since before this last zoom action we were displaying the bottom-right 100x100 rectangle within a 200x200 content rectangle). So the x coordinate of the final rectangle becomes: center.x/currentScale - (scrollView.frame.size.width/2) + scrollView.contentOffset.x/currentScale = 75/.5 - 100/2 + 100/.5 = 150 - 50 + 200 = 300. In this case, being a square, the calculation for the y coordinate is the same. And we did indeed zoom in the bottom-right 100x100 rectangle, which, in the larger 400x400 content view has origin 300,300. So here is how you would calculate the zoom rectangle's size and origin: zoomRect.size.height = mScrollView.frame.size.height/scale; zoomRect.size.width = mScrollView.frame.size.width/scale; <pre><code>zoomRect.origin.x = center.x/currentScale - (mScrollView.frame.size.width/2) + mScrollView.contentOffset.x/currentScale; zoomRect.origin.y = center.y/currentScale - (mScrollView.frame.size.height/2) + mScrollView.contentOffset.y/currentScale; </code></pre> Hope this made sense; it's hard to explain it in writing without sketching out the various squares/rectangles. Cheers, Raf Colasante
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POUIScrollView zoomToRect not zooming to given rect (created from UITouch CGPoint)
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USRaffaello Colasante
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PostsAcceptedAnswerId
1. This table or related slice is empty.
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1. This table or related slice is empty.
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1. This table or related slice is empty.
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1. This table or related slice is empty.

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