I am using CATiledLayer to display a pdf page..
But the layer do have some time to draw context.
Therefore, I try to add an background beside this layer and remove the background after CATiledLayer is successful display..
My question is Is there any ways to detect the drawing status of CATiledLayer?
Thanks for your help.
subclass your CATiledLayer and make fadeDuration of tiledlayer to 0.0
A "hacky" way of doing is to pre-calculate how much tiles will be rendered, and then count the calls to - (void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context. It's a pretty insecure though and most likely only works on the initial zoom level. CATiledLayer caches its tiles and doesn't tell you what is cached and what will be redrawn.
Related
I am creating a simple photo filter app for OS X and I am displaying a photo on an NSImageView (actually two photos on top of each other with two NSImageViews, but the question still applies for a single view too). Everything works super, but when I try to resize the window that contains the NSImageViews, the window (which also resizes the NSImageViews) resizes very slowly, at about less than 1fps, creating a negative impact on the user experience. I want resizing windows to be as smooth as possible. When I disable resizing the image views, the window resizes smoothly, so the cause of the slowdown is those NSImageViews.
I'm loading 20-megapixel images from my DSLR. When I scale them down to a reasonable size for screen (e.g. 1024x768), they scale smoothly, so the problem is the way NSImageView renders the images. It (I assume as the result of this behavior) tries to re-render 20MP image every time it needs to redraw it into whatever the target frame of the view is.
How can I make NSImageView rescale more smoothly? Should I feed it with a scaled-down version of my images? I don't want to do that as it's a photo editing app that also targets retina display screens and the viewport would actually be quite large. I can do it, but it's my final option. Other than scaling down, how can I make NSImageView resize faster?
I believe part of the solution your are looking for is in NSImage's representations. You can add many representations to an image with addRepresentation: I believe there is some intelligent selection done when drawing. In your case, I think you would need to add both representations (the scaled-down and the full resolution bitmap) to NSImage. I strongly suspect drawRect: should pick the low resolution version. I would make sure "scale up or down" is selected in NSImageView, because the default is scale down only, which may force your full resolution image to be used most of the time. There are some discussion in Apple's documentation regarding "matching" under "Setting the Image Representation Selection Criteria" in NSImage, although at first sight this may not be sufficient.
Then, whenever you need to do something with the full image, you would request the full resolution image by going through the representations ([NSImage representations] returns an array of NSImageRep).
I have a large image managed with CATiledLayer (like the Large Image Downsizing iOS sample code).
I had a drawing view (UIView overrided with drawing methods) on it but when I zoom a lot, I get the following message and my view disappeared..
-[<CALayer: 0xb253aa0> display]: Ignoring bogus layer size (25504.578125, 15940.361328)
Is there a way to avoid this ?
Sounds like the levelsOfDetail and levelsOfDetailBias you are setting are allowing for more zoom than the tiled layer should allow given the max layer size allowable for the layer. Try changing those to lessen how much the user can zoom.
Here is a great article explaining some of the undocumented behavior of CATiledLayer.
I have several UIButtons on a UIScrollView. I want the buttons to have rounded corners, so I call maskToBounds: on each of them. When I do this and run on the device, the scrolling framerate is pretty bad (it works fine on the simulator). Any ideas on a workaround for this problem?
You're causing the view to be composited offscreen with that call to masksToBounds:, which slows things down quite a bit. Are you rendering custom button images? If so use UIImage -stretchableImageWithLeftCapWidth:topCapHeight: with an image which is the minimum width to encompass it's rounded edges. This allows the GPU to handle stretching the image in the most efficient way possible, while still giving you a button made out of an image. There is a session in the WWDC 2011 videos on Drawing in UIKit - watch that, as it addresses exactly this problem, and a few others you're likely to have.
A few alternative methods:
Tweeties implementation of fast scrolling, by drawing everything manually
Matt Gallaghers implementation of custom drawing. This is the method I use, as it's easy to maintain
I have a list of images (say 180 images of sequence) to animate. If I use UIImageView with its default image sequence, I get memory issue.
I wanted to use CoreAnimation API, but really don't know how to do it?
What is the best way to do this.
Regards
iWasRobot :P
There's a very hard to google example on how to perform view transitions with Animation, here it is:
http://developer.apple.com/library/ios/#samplecode/ViewTransitions/Introduction/Intro.html
Here you would need as little as 2 views. You would load images into the hidden view, then "transition" it in. Assuming your slideshow mode is long enough, you should have no issues with loading times.
Another thing that comes to mind is paging with UIScrollView. Here you would need as little as 3 views
http://ykyuen.wordpress.com/2010/05/22/iphone-uiscrollview-with-paging-example/
I hope this helps!
I'm trying to use a CAGradientLayer as a background for a UITableView. Everything works well until the overlaying view is scrolled, at which point then the pre-rendered background scrolls up and out of the way along with the original screen of data.
This is code that is being migrated from an iOS 3.1.3 app using a UIImage as a background to something device/resolution independent-looks great, works well, but sniffing the device type and using an alternate png isn't the sort of code that I want to ship, much less maintain.
Any suggestions as to how to do this?
Found the solution to what I was trying to solve, courtesy of Matt Gallagher:
http://cocoawithlove.com/2009/08/adding-shadow-effects-to-uitableview.html
His blog post has quite a few nice touches, including shadowing relevant cells instead of the whole table (mentioned as a performance issue in Noah's response).
You may have to make the table view transparent, and add the gradient layer to the table's superview. Keep in mind that your scrolling performance is probably going to be hideous—Core Animation will have to composite every subview of the table for every frame it displays. You may be able to slightly mitigate this by setting the cells' layers to rasterize themselves, as described here, but expect things to be pretty choppy regardless.