Why UIImageJPEGRepresentation and UIImagePNGRepresentation increase data size?

Asked Feb 20 '17 at 14:13

Active Feb 20 '17 at 19:16

Viewed 718 times

Doing a image scaling to have image limit in 320x480, so w <= 320 and h <= 640. But after conversion to data and back conversion to image I get a twice as big image as it was originally. Why? How can I avoid? Should use 160x320 size to get the required size?

let s = CGSize(width: w, height: h)
UIGraphicsBeginImageContextWithOptions(s, false, 0.0);
image.draw(in: CGRect(x: 0, y: 0, width: w, height: h))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext();

let data2 = UIImageJPEGRepresentation(newImage!, 1.0)!
let image3 = UIImage(data: data2)

(lldb) po newImage!.size ▿ (320.0, 213.5) - width : 320.0 - height : 213.5

(lldb) po image3!.size ▿ (640.0, 427.0) - width : 640.0 - height : 427.0

edited Feb 20 '17 at 18:54

Andrew Vergunov

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asked Feb 20 '17 at 14:13

János

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Check scale property on both images. I think you will see 2 on first and 1 on second. – Sergey Feb 20 '17 at 14:26
Right, 2, and 1. What to do? – János Feb 20 '17 at 14:36
http://stackoverflow.com/questions/9274234/uigraphicsgetimagefromcurrentimagecontext-retina-resolutions ? – Larme Feb 20 '17 at 14:37
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Try UIGraphicsBeginImageContextWithOptions(s, false, image.scale); – Sergey Feb 20 '17 at 14:59

Why UIImageJPEGRepresentation and UIImagePNGRepresentation increase data size?

0 Answers0