Using ALAssetsLibrary the Thumbnail images takes time to load.is there any solution to load images faster.
the images are more than 900 images in photos.
Code:
[ALAssetsGroupObj enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger i, BOOL *load)
{
if(asset == nil)
{
asset;
}
UIImage* thumbImage = [UIImage imageWithCGImage:[asset thumbnail]
}
Thanks
No, there is no way to make it go any faster. But there are a few tricks:
Cache them to a static NSDictionary. Next time you'll need to draw them in your app, it will be much faster than pulling them from the library. I've tried with far more than 900 thumbnails.
Your screen won't fit 900 thumbs. As the user scrolls, you can populate the images in blocks and load say 16-32 or so per time. This is a bit tricky though as both the operation to draw the thumbnails and the scrolling needs to run on the main thread.
Related
I have a gallery view of photos that are downloaded from the internet so I used Enormego's EGOImageView. I noticed that when i scrolled down my tableview after the images were in the cache, the scrolling would lag. I immediately found that when the image was retrieved from the hard drive with return [UIImage imageWithContentsOfFile:cachePathForKey(key)]; it was working on the main thread so I added the operation to an NSOperationQueue. This reduced the lag by half but the scrolling still stuttered. After going through the code, I noticed that in the success method
- (void)imageLoaderDidLoad:(NSNotification*)notification {
if(![[[notification userInfo] objectForKey:#"imageURL"] isEqual:self.imageURL]) return;
UIImage* anImage = [[notification userInfo] objectForKey:#"image"];
self.image = anImage;
[self setNeedsDisplay];
if([self.delegate respondsToSelector:#selector(imageViewLoadedImage:)]) {
[self.delegate imageViewLoadedImage:self];
}
}
commenting out the self.image = anImage; got rid of the lag completely (but obviously I get no image). And as far as I can tell, if I want to alter the UI, it must be done in the main thread. Is there a way to set the image for the EGOImageView without it lagging the scrolling?
Note: the JPGs are around 50kB
Thanks
Subclass uitableViewCell and do your own drowing in drawContentView.
Resize images in background thread and then present them in cells.
P.S: if the code found on git hub is not good enough for you, try to write your own that suits your problem.
From what I understand, all the steps required to initiate an asynchronous disk query takes a couple milliseconds on the mainthread, and that is enough time for the scrolling to look like it stutters, so I decided to completely remove hard drive caching for large images and instead create an NSMutableDictionary which holds the UIImage as an object, and the NSURL.absoluteString as the key. This works seamlessly but obviously has the disadvantage of being a memory hog. I checked out the memory usage of some photo-sharing apps and I've been able to get the memory usage for the app to over 100MB so it seems everybody else is doing this.
I am loading image with data in my table view. Images are coming from web. I created method to get image url in model class.Model class has Nsdictionary and objects.
But this images is slowing down scrolling .Here is my code
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",
[(Tweet *)[recentTweets objectAtIndex:indexPath.row]urlString]]]]];
cell.imageView.image = image;
Please tell Where I am going wrong?
Use lazy loading and do your own drawing. Try to understand the techniques on the sample projects I linked. These are the best ways to improve the performance of tables with images.
here is the methodology I use for loading images into a UITableView from a remote location:
in your .h file, declare a mutable dictionary for storing the images:
NSMutableDictionary *images;
initialize the dictionary in -init... or in -viewDidLoad
images = [[NSMutableDictionary alloc]init];
in the .m, tableView:cellForRowAtIndexPath:, see if the image exists in your dictionary for the indexPath
UIImage *img = [images objectForKey: indexPath];
if the image does exist, just set it.
if (img) cell.imageView.image = img;
if the image does NOT exist, set the cell's image to a temporary image...
if (!img) cell.imageView.image = [UIImage imageNamed:#"imageUnavailable.png"];
AND add that image to your dictionary so it doesnt try to refetch the image if you scroll off and back to that image before it loads...
[images setObject:[UIImage imageNamed:#"imageUnvailable.png"] forKey: indexPath];
then, in this same block, use an NSOperationQueue, and a custom NSOperation ( here is a reference - NSOperation and SetImage) to get your image and call back into your UITableViewController with that image.
in your callback, add your image to the dictionary (overwriting the temp image) and call [tableView reloadData]
this will give you a nice non blocking user experience.
The are a couple of ways how to do it. I had the best experience with a Queue for the HttpRequests, which I pause during the scrolling process.
I highly recommend this framework for that:
http://allseeing-i.com/ASIHTTPRequest/
I also implemented an image cache, which only loads the images if there weren't in the cache.
And the last tweak was to actually draw the images instead of using a high level uicomponent like the UIImageView
The number one reason your code is slow right now is because you're making a network call on the main thread. This blocks an UI from being updated and prevents the OS from handling events (such as taps).
As already suggested, I recommend ASIHTTPRequest. Combine asynchronous requests with an NSOperationQueue with a smaller concurrency count (say, 2) for the image requests, caching, and reloading the rows when images come in (on the main thread) (also only reloading the row if its currently visible). You can get a smooth scrolling table view.
I have an example of this on github here: https://github.com/subdigital/iphonedevcon-boston
It's in the Effective Network Programming project and includes a set of projects that progressively improve the experience.
Download the images before you load the tableView, and store them in an NSArray. Then when the cellForRowAtIndexPath method is called, show a loading image until the image is in the array.
When I am scrolling images frequently in a UIScrollView then after some images, the next image takes time to load... it's not taking too much time but looks odd.
Suppose I have 27 images in a scrollView. When I start to scroll these images, for 1 or 2 images it scrolls smoothly but when I scroll again to see the 3rd image it takes time to load. Then when I start the images scrolling again from the 3rd image, it behaves like before.
I can't load all 27 images at a time or my app crashes.
When I slowly scroll the scrollview then I don't have this problem.
My code is below:
//Taking image view for 27 images;
int x=0;
for(int i = 1; i<=27; i++) {
imageView = [[UIImageView alloc] init];
imageView .frame = CGRectMake(x,0,768,1024);
imageView.tag=i;
imageView.image=nil;
imageView.userInteractionEnabled=YES;
[contentView addSubview:imageView];
x+=768;
}
//setContentOffset of the scrollView -->ContentView
[contentView setContentOffset: CGPointMake((imageNumber-1)*768, 0) animated: YES];
//desire image which i want to see from the start of the scrollview
pageNumber=imageNumber;
int pageBefore=pageNumber-1;
int pageAfter=pageNumber+1;
//Views for image
for( UIImageView * views in [contentView subviews]){
if(views.tag==pageNumber){
if(views.image==nil){
NSLog(#"entering");
views.image=[UIImage imageNamed:[ NSString stringWithFormat:#"%d.jpg",pageNumber]];
[views.image release];
}
}
if(views.tag==pageBefore){
if(views.image==nil){
views.image=[UIImage imageNamed:[ NSString stringWithFormat:#"%d.jpg",pageBefore]];
[views.image release];
}
}
if(views.tag==pageAfter){
if(views.image==nil){
views.image=[UIImage imageNamed:[ NSString stringWithFormat:#"%d.jpg",pageAfter]];
[views.image release];
}
}
My alarm bells rang when I saw this;
imageView .frame = CGRectMake(x,0,768,1024);
Apart from the space before .frame, are you saying that your images are 768x1024? That's HUGE and I suspect your problems are memory ones rather than code ones.
Be aware that in particular, using UIImage imageNamed: is likely to cause grief with such large images as that method caches the images in memory. You may wish to consider using alternative methods that load the image from a file each time.
You should try use the EGOImageView, it has caching build in which might help with your performance issues. You can implement a placeholder image to show the user that an image is being prepared for viewing. The image will load in another thread before being displayed, giving you smoother scrolling performance. The EGOImageView is part of the EGOImageLoading library.
https://github.com/tastefulworks/EGOImageLoading
As an alternative you could create your own lazy loading mechanism to increase scrolling performance. E.g. once a user stops scrolling for a second, start loading the image, otherwise display placeholder image if not yet the correct image is cached.
Edit: when thinking more about this issue, I realize caching won't help much (since you already load image from disk), but the asynchronous loading of images should help with the scroll performance, so make use of NSThread or NSOperation to load the image in a background thread, then notify the main thread that the image is loaded and ready for display.
So this one is pretty odd ad I'm not sure if the trouble is with the AssetsLibrary API, but I can't figure out what else might be happening.
I am loading an array with ALAssets using the -enumerateAssetsUsingBlock method on ALAssetsGroup. When it completes, I am loading a custom image scroller. As the scroller finishes scrolling, I use NSInvocationOperations to load the images for the currently visible views (pages) from the photo library on disk. Once the image is loaded and is cached, it notifies the delegate which then grabs the image from the cache and displays it in an image view in the scroller.
Everything works fine, but the time it takes from when -setImage: actually gets called to the time it actually shows up visibly on the screen is unbearable--sometimes 10 seconds or more to actually show up.
I have tried it both with and without image resizing which adds almost nothing to the processing time when I do the resizing. As I said, the slowdown is somewhere after I call -setImage on the image view. Is anyone aware of some sort of aspect of the AssetLibrary API that might cause this?
Here's some relevant code:
- (void)setImagesForVisiblePages;
{
for (MomentImageView *page in visiblePages)
{
int index = [page index];
ALAsset *asset = [photos objectAtIndex:index];
UIImage *image = [assetImagesDictionary objectForKey:[self idForAsset:asset]];
// If the image has already been cached, load it into the
// image view. Otherwise, request the image be loaded from disk.
if (image)
{
[[page imageView] setImage:image];
}
else {
[self requestLoadImageForAsset:asset];
[[page imageView] setImage:nil];
}
}
}
This will probably mess up any web searches looking to solve problems with the AssetsLibrary, so for that I apologize. It turns out that the problem wasn't the AssetsLibrary at all, but rather my use of multi-threading. Once the image finished loading, I was posting a notification using the default NSNotificationCenter. It was posting it on the background thread which was then updating (or trying to update, at least) the UIImageView with -setImage. Once I changed it to use -performSelectorOnMainThread and had that selector set the image instead, all was well.
Seems no matter how familiar I get with multi-threading, I still forget the little gotchas from time to time.
I have a tableView with some large images in it. I'm struggling to improve the very jerky scrolling performance. If I use ImageNamed to load the images, scrolling is jerky at first, but after the images are viewed, scrolling is smooth. I know ImageNamed adds the images into the system cache, so my question is: is it possible to pre-load the images into the system cache before they are viewed?
I've tried by adding the following code to my viewDidLoad method:
for (int i = 0; i < appDelegate.detailSectionsDelegateDict.count; i++) {
NSString *imageString = [NSString stringWithFormat:#"%#",[[appDelegate.detailSectionsDelegateDict objectAtIndex:i] objectForKey:#"MainTrackImage"]];
NSString *bundlePath = [[NSBundle mainBundle] bundlePath];
UIImage* theImage;
theImage = [UIImage imageNamed:imageString];
[imageCacheArray insertObject:theImage atIndex:i];
}
I then draw the correct image from the imageCacheArray in my CellForRowAtIndexPath method. But the result is still jerky scrolling.
Thanks!
Getting a table view with images (especially large ones) to scroll smoothly is not as trivial as you might think. Loading up a bunch of images with [UIImage imageNamed:] will very quickly cause springboard to kill your app as it starts to exceed memory capacity. Take a look at the Core Animation session videos from this year's WWDC, specifically look at session 425, "Core Animation in Practice, Part 2" They cover this exact topic and it's very well done. You can also get the relevant source code if you sign in with your developer account.