CODEWITHSUNDEEP
iphoneoptimizationgraphicsresizeuiimage
Oliver
Oliver

Reputation: 23510

iPhone - Resizing an UIImage in less than a second on an iPhone 4

I have a 5MP image coming from the back camera. I want to downsize it to put it into an ImageView without having to wait too long (it take a logn time to the UIImageView to display a 5 MP picture). So I tried many methods to resize / resample the image to make it fit a just-screen resolution (retina one). But it take around 1 sec to downsize the image.

Would you know any optimised way to be able to resize this 5MP image to the retina 960 x 640 resolution as fast as possible, and at least at less that 0.7 sec on an iPhone 4 ?

Upvotes: 1

Views: 3895

Answers (2)

Joris Kluivers
Joris Kluivers

Reputation: 12081

You're displaying an image in an UIImageView. I understand you want a version that is equal to the size of the screen. The way I would do it: display the original image in the UIImageView directly, this shouldn't take any noticeable amount of time.

Then in a background thread resize the same image down to the size you want and update the UIImageView as soon as that is done.

This gives you something on screen immediately while you generate an optimized version at the same time.

I don't know if you are using the original image for something else, but if you really only want the screen sized image it might be an idea to use an AVCaptureSession with a preset of AVCaptureSessionPresetHigh (see AVCaptureSession sessionPreset). This setting results in a more reasonably sized image, which might better suit your needs.

Upvotes: 0

XJones
XJones

Reputation: 21967

This is my favorite blog post and code to resize images. I haven't benchmarked it but I know of no faster way.

http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/

Upvotes: 6

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