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I am interested how does iPhone built in photos app changes the clock's color when I previewing an image as a wallpaper. I have been searching for 2 days but no success. I understand that the method should analyze pixel's color behind the label. But going through each pixel seems to be inefficient. Could somebody guide me through this?

efimovdk
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  • How does clock's color changes? Could you please elaborate a bit, for instance by uploading a snapshot? – Munahil Aug 06 '15 at 09:18
  • What's behind the label? Is it a UIImageView? This talks about how to get RGB from a UIImage at specific pixel positions. http://stackoverflow.com/questions/448125/how-to-get-pixel-data-from-a-uiimage-cocoa-touch-or-cgimage-core-graphics – mxs Aug 06 '15 at 09:19
  • @Munahil It changes dynamically. When you drag a photo and something too bright appears behind the label turns to black, otherwise white. I don't have the phone right now. – efimovdk Aug 06 '15 at 09:27
  • @MikeStrand suppose I got those RGBA values but what's next? – efimovdk Aug 06 '15 at 09:28
  • You would programmatically set the label text color with something like http://stackoverflow.com/questions/2532409/can-not-change-uilabel-text-color – mxs Aug 06 '15 at 09:33
  • @MikeStrand you didn't get the idea. I don't have just a point. I have a rectangle which is UILabel's frame. Thus, base on the color of the rect(which can consist of many colors), I need to setup label's color. The only reason I am asking this question is I want to know what to do. Should I calculate an average color or what and e.t.c – efimovdk Aug 06 '15 at 09:37
  • I guess it depends on the visual effect you want, but yeah - getting an average would be a good start and then picking something in contrast I'm guessing is what you want. https://github.com/mxcl/UIImageAverageColor/blob/master/UIImage%2BAverageColor.m – mxs Aug 06 '15 at 09:43
  • I think, you are looking for this: [color from background image][1] [1]: http://stackoverflow.com/questions/19456288/text-color-based-on-background-image – Bhanupriya Aug 06 '15 at 09:54

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