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copied!<p>I had the exact same problem, cured by avoiding the triggering of Core Image filters during cell updates. </p> <p>The Apple docs stuff about lazy evaluation / recipes is, I think, more directed at the idea that you can chain core image filters together very efficiently. However, when you want to display the results of a core image filter chain, the thing needs to be evaluated then and there, which is not a good situation if the 'then and there' is during a rapidly-scrolling view and the filter in question requires heavy processing (many of them do).</p> <p>You can try fiddling with GPU vs CPU processing, but I have found that the overhead of moving image data to and from CIImage can be a more significant overhead (see my answer <a href="https://stackoverflow.com/a/16206120/1375695">here</a>)</p> <p>My recommendation is to treat this kind of processing the same way as you would treat the populating of a scrolling view with online images - i.e. process asynchronously, use placeholders (eg the preprocessed image), and cache results for reuse.</p> <p><em>update</em></p> <p>in reply to your comment:</p> <p>Applicable filters are applied when you extract data from the CIImage - for example, with <code>imageWithCIImage:</code> [warning - this is my inference, I have not tested]. </p> <p>But this is not your problem... you need to process your images on a backgound thread as the processing will take time that will hold up the scrolling. Meanwhile display something else in the scrolling cell, such as a flat color or - better - the UIImage you are feeding into your CIImage for filtering. Updated the cell when the processing is done (check to see if it still needs updating, it may have scrolled offscreen by then). Save the filtered image in some kind of persistent store so that you don't need to filter it a second time, and check the cache whenever you need to display the image again before reprocessing from scratch.</p>

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