How to get [UIImage imageWithContentsOfFile:] and High Res Images working

objective-c uiimage ios4 high-resolution imagenamed
Marin Todorov picture Marin Todorov · Sep 18, 2010 · Viewed 27k times · Source

As many people are complaining it seems that in the Apple SDK for the Retina Display there's a bug and imageWithContentsOfFile actually does not automatically load the 2x images.

I've stumbled into a nice post how to make a function which detects UIScreen scale factor and properly loads low or high res images ( http://atastypixel.com/blog/uiimage-resolution-independence-and-the-iphone-4s-retina-display/ ), but the solution loads a 2x image and still has the scale factor of the image set to 1.0 and this results to a 2x images scaled 2 times (so, 4 times bigger than what it has to look like)

imageNamed seems to accurately load low and high res images, but is no option for me.

Does anybody have a solution for loading low/high res images not using the automatic loading of imageNamed or imageWithContentsOfFile ? (Or eventually solution how to make imageWithContentsOfFile work correct)

Answer

Marin Todorov picture Marin Todorov · Sep 18, 2010

Ok, actual solution found by Michael here : http://atastypixel.com/blog/uiimage-resolution-independence-and-the-iphone-4s-retina-display/

He figured out that UIImage has the method "initWithCGImage" which also takes a scale factor as input (I guess the only method where you can set yourself the scale factor)

[UIImage initWithCGImage:scale:orientation:]

And this seems to work great, you can custom load your high res images and just set that the scale factor is 2.0

The problem with imageWithContentsOfFile is that since it currently does not work properly, we can't trust it even when it's fixed (because some users will still have an older iOS on their devices)

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