Thanks a lot for your response! I have tried the CILanczosScaleTransform filter for downsizing. I have computed the scale factor exactly such that the new image has an extent not larger than the view. (Below is my code) But the performance was worse, at least with the software renderer. With the hardware renderer (kCIContextUseSoftwareRenderer: @NO), performance was as before, but visual artifacts were still much worse than without any downsizing.
If you are curious: here is a video showing the performance https://owncloud.informatik.uni-bremen.de/index.php/s/wJRkK8Ek2HTp32a (The video was made with the software renderer.) So, right now, I am using this code: NSDictionary * imageOpts = @{ (id)kCGImageSourceCreateThumbnailWithTransform: (id)kCFBooleanTrue, // takes care of EXIF orientation, too (id)kCGImageSourceCreateThumbnailFromImageIfAbsent: (id)kCFBooleanTrue, (id)kCGImageSourceCreateThumbnailFromImageAlways: (id)kCFBooleanTrue, (id)kCGImageSourceShouldCacheImmediately: (id)kCFBooleanTrue, (id)kCGImageSourceThumbnailMaxPixelSize: @(8192) }; CGImageRef newImageRef = CGImageSourceCreateThumbnailAtIndex( new_image, 0, (__bridge CFDictionaryRef) imageOpts ); There is still a bit of stuttering. Maybe, it would help to create the CALayer for the new images in the background thread and add it to the layer hierarchy, but I haven't explored this option yet. Maybe it would not help, because, maybe, at that point some process in the foreground would kick in again, over which I would not have control. Best regards, Gabriel Encl.: Just for your reference, this is my code for downsizing using the Lanczos filter: CIContext * ciContext = [CIContext contextWithOptions: @{kCIContextUseSoftwareRenderer: @NO} ]; // TODO: als inst.var. machen! // TODO: evtl im context kCIContextPriorityRequestLow und useSoftwareRenderer=FALSE angeben? CIFilter * resizeFilter = [CIFilter filterWithName: @"CILanczosScaleTransform" ]; [resizeFilter setValue: orientedimage forKey: kCIInputImageKey]; [resizeFilter setValue: @(scale) forKey: kCIInputScaleKey ]; [resizeFilter setValue: @(aspect) forKey:kCIInputAspectRatioKey ]; CIImage * resizedImage = resizeFilter.outputImage; CGImageRef newImageRef = [ciContext createCGImage: resizedImage fromRect: resizedImage.extent]; > > Since this stutter does not occur when cycling back through images that have > already been assigned to the layer, it’s possible that if the size of the > CGImageRef does not match the size of the CALayer, there may be some kind of > render occuring, especially if the image is being scaled to fit the layer. > Do images much larger than the CALayer stutter more? > > Also, if you’re resizing, you’ll want to use CIImage’s > CILanczosScaleTransform filter. Simply scaling a using a transform will give > you a much blurrier image. > > Jim Crate > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
