How to reuse a UIImage - iphone

I'm using some sample code I got from a tutorial to create basically a snapshot using AVCamRecorder. It doesn't save a picture, it just displays it in a little rect under the live camera view whenever I click a button. It seemed to be allocating more and more memory each time I clicked the button to update the image, so I put an if (image) {[image release]} and then continued with the rest of the code to capture the image. The problem I ran into there is that eventually I hit an EXC_BAD_ACCESS if I click the button fast enough repeatedly. I tried inserting an if (image) immediately before assigning it to my view, but I still get EXC_BAD_ACCESS. I tried adding an [NSThread sleepForTimeInterval:1] at the end, but that didn't help either. I still get the EXC_BAD_ACCESS after clicking the button several times. Is there a proper way to reuse this view? Thanks
if (image) {
[image release];
exifAttachments = nil;
}
[[self stillImageOutput] captureStillImageAsynchronouslyFromConnection:stillImageConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
exifAttachments = CMGetAttachment(imageDataSamplebuffer, kCGImagePropertyExifDictionary, NULL);
if (exifAttachments) {
// NSLog
} else {
// NSLog
}
NSData *imagedata = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
image = [[UIImage alloc] initWithData:imageData];
if (image) {
self.capturedPicView.image = image;
}
}];`

Is the image variable declared as __block? If not, you may get all sorts of weird things because you can't modify it within a block.
You probably don't need a separate image variable - just do:
self.capturedPicView.image = [[[UIImage alloc] initWithData:imageData] autorelease];
in your block.
P.S. And it looks like your original memory leak was due to not releasing the new image - you could have added autorelease to UIImage creation or just release it right after assigning (UIImageView.image retains it anyway):
image = [[UIImage alloc] initWithData:imageData];
if (image) {
self.capturedPicView.image = image;
[image release];
}

Related

Add image to photo library from bundle when purchased

Like in templeRun, we also wish to add inAp purchase to give image.
http://www.youtube.com/watch?v=dYog6yhs0y4
How can I download image placed inside game bundle to iphone's photo library?
Call UIImageWriteToSavedPhotosAlbum , which I believe looks like this:
UIImageWriteToSavedPhotosAlbum(
UIImage* image,
id completionTarget,
SEL completionSelector,
void* contextInfo
);
One way to use it is like this:
UIImage* myImage = [UIImage imageNamed:#"image.png"];
UIImageWriteToSavedPhotosAlbum(myImage, self, #selector(image:didFinishSavingWithError:contextInfo), nil);
You only need to set the completion target and completion selector if you want to be notified if it succeeded or failed. If so, don't forget to add this method to the class:
- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void*)contextInfo
{
if (error)
{
// Do something on error... (like show a UIAlert for example)
}
else
{
// Do something on success... (maybe show a "Your image was saved" alert
}
}
The image doesn't save right away and might error in the process so this can be useful.
You can also use the ALAssetsLibrary, which I believe would look like this:
ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
[library writeImageToSavedPhotosAlbum:[myImage CGImage] orientation:(ALAssetOrientation)[myImage imageOrientation] completionBlock:^(NSURL* assetURL, NSError* error)
{
if (error)
{
// Do something on error... (like show a UIAlert for example)
}
else
{
// Do something on success... (maybe show a "Your image was saved" alert
}
}];
Hope this helped.
Create a UIImage object from the picture within your bundle using imageNamed: and then use UIImageWriteToSavedPhotosAlbum() to save it to the Photo Library.
UIImage *image = [UIImage imageNamed:#"wallpaper.jpg"];
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
For more information on the options for UIImageWriteToSavedPhotosAlbum() (callback functions, etc.) you can take a look at the UIKit Function Reference.

objective - C : Loading image from URL?

Sorry for question title. I can not find a suitable title.
I have UITableView content images from url when i open the UITableView the View did not show until the images loaded and that takes along time.
I get the images from JSON by php.
I want to show the table and then images loading process.
This is code from my app:
NSDictionary *info = [json objectAtIndex:indexPath.row];
cell.lbl.text = [info objectForKey:#"title"];
NSString *imageUrl = [info objectForKey:#"image"];
cell.img.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]]];
[cell.img.layer setBorderColor: [[UIColor blackColor] CGColor]];
[cell.img.layer setBorderWidth: 1.0];
return cell;
Sorry my english is weak.
Perform the web request on a separate thread, to not block the UI. Here is an example using NSOperation. Remember to only update the UI on the main thread, as shown with performSelectorOnMainThread:.
- (void)loadImage:(NSURL *)imageURL
{
NSOperationQueue *queue = [NSOperationQueue new];
NSInvocationOperation *operation = [[NSInvocationOperation alloc]
initWithTarget:self
selector:#selector(requestRemoteImage:)
object:imageURL];
[queue addOperation:operation];
}
- (void)requestRemoteImage:(NSURL *)imageURL
{
NSData *imageData = [[NSData alloc] initWithContentsOfURL:imageURL];
UIImage *image = [[UIImage alloc] initWithData:imageData];
[self performSelectorOnMainThread:#selector(placeImageInUI:) withObject:image waitUntilDone:YES];
}
- (void)placeImageInUI:(UIImage *)image
{
[_image setImage:image];
}
You have to use NSURLConnection and NSURLRequest. First create and show your empty table view (maybe with placeholder images, that are stored locally in the app). Then you start sending requests. These requests will run in the background and you (the delegate) will be notified when a request is completed. After that you can show the image to the user. Try not to load all the images at once if you have a lot of them. And don't load the ones that are invisible to the user, only load those if he scrolls down.
There is a UITableView lazy image loading example that Apple provided: https://developer.apple.com/library/ios/#samplecode/LazyTableImages/Introduction/Intro.html
Hopefully it's what you were looking for
This is among very common thing we do in our application.
You simply can have store the URLs in a persistent store e.g array or db & can get the images using Operation queue to download faster. You can set the priorities, cancel operations at anytime etc. Also, the application respond time will be quicker.

Error 133000 when using multiple contexts with core data

I've spent days trying every possible solution I can think of to this problem, but nothing seems to be working.
I run a background thread like this:
[MagicalRecord saveInBackgroundWithBlock:^(NSManagedObjectContext *localContext) {
Media *localMedia = [media inContext:localContext];
UIImage *image = localMedia.thumbnail;
dispatch_async(dispatch_get_main_queue(), ^{
[thumbnails setObject:image forKey:[NSNumber numberWithInt:i]];
[contentDict setObject:thumbnails forKey:#"MediaItems"];
[cell.entryView setNeedsDisplay];
});
}];
Or like this:
dispatch_queue_t cellSetupQueue = dispatch_queue_create("com.Journalized.SetupTimelineThumbnails", NULL);
dispatch_async(cellSetupQueue, ^{
NSManagedObjectContext *newMoc = [[NSManagedObjectContext alloc] init];
NSPersistentStoreCoordinator *coordinator = [NSManagedObjectContext contextForCurrentThread].persistentStoreCoordinator;
[newMoc setPersistentStoreCoordinator:coordinator];
NSNotificationCenter *notify = [NSNotificationCenter defaultCenter];
[notify addObserver:self
selector:#selector(mergeChanges:)
name:NSManagedObjectContextDidSaveNotification
object:newMoc];
Media *localMedia = [media inContext:[NSManagedObjectContext contextForCurrentThread];
UIImage *image = localMedia.thumbnail;
dispatch_async(dispatch_get_main_queue(), ^{
[thumbnails setObject:image forKey:[NSNumber numberWithInt:i]];
[contentDict setObject:thumbnails forKey:#"MediaItems"];
[cell.entryView setNeedsDisplay];
});
}];
Both of these give me a crash with UIImage returning as nil object, and a Cocoa Error 133000.
I've removed every other piece of background threading code, and have saved on the main thread directly before this just to make sure. Running the code above on the main thread also works, but freezes up my UI. Despite all of these efforts, the above code crashes every time.
I'm not sure what to do to make this work.
Edit:
My question, specifically, is how do I make this work without crashing? It seems to be a problem with objects from 1 context not existing in another, but how do i make them exist in another context?
Remember, the MR_inContext: method is using [NSManagedObjectContext objectWithID: ] method under the covers. You should look in there to make sure your object has:
1) Been saved prior to entering into the background context/block in your first code block
2) This method is returning something useful
I'm also not sure how you set up your thumbnail attribute. Ideally it shouldn't matter as long as you have the NSTransformable code write (there are samples on the internets that show you how to save a UIImage in core data using the transformable attribute)
Also, your code should look like this:
UIImage *image = nil;
[MagicalRecord saveInBackgroundWithBlock:^(NSManagedObjectContext *localContext) {
Media *localMedia = [media inContext:localContext]; //remember, this looks up an existing object. If your context is a child of a parent context that has contains this, the localContext should refresh the object from the parent.
//image processing/etc
image = localMedia.thumbnail;
} completion:^{
[thumbnails setObject:image forKey:#(i)]; //new literals are teh awesome
contentInfo[#"MediaItems"] = thumbnails; //as is the new indexer syntax (on the latest compiler)
[cell.entryView setNeedsDisplay];
}];
Fast answer:
NSManagedObjectReferentialIntegrityError = 133000,
// attempt to fire a fault pointing to an object that does not exist (we can see the store, we can't see the object)
EDIT:
It's pretty difficult to see something from the code. What is a managed object there?
I suppose the problem is that you are using temporary objects from one context in another context.

How to know when UIimageView finished loading?

In my view controller, how can I know when a certain UIImageView has finished loading (large jpeg from documents directory)? I need to know so that I can then swap a placeholder low-res imageview with this hi-res imageview. Do I need to create a custom callback to know this? Any way is fine.
By the way, here is a snippet of code where I load the image:
NSString *fileName = [NSString stringWithFormat:#"hires_%i.jpg", currentPage];
NSString *filePath = [NSString stringWithFormat:#"%#/BookImage/%#", [self documentsDirectory], fileName];
hiResImageView.image = [[[UIImage alloc] initWithContentsOfFile:filePath] autorelease];
UIImageView isn't doing any loading at all. All the loading is being done by [[UIImage alloc] initWithContentsOfFile:filePath], and your thread is blocked while the file is loaded (so the load is already complete by the time that call finally returns).
What you want to do is something like this:
- (void)loadImage:(NSString *)filePath {
[self performSelectorInBackground:#selector(loadImageInBackground:) withObject:filePath];
}
- (void)loadImageInBackground:(NSString *)filePath {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
UIImage *image = [[UIImage alloc] initWithContentsOfFile:filePath];
[self performSelectorOnMainThread:#selector(didLoadImageInBackground:) withObject:image waitUntilDone:YES];
[image release];
[pool release];
}
- (void)didLoadImageInBackground:(UIImage *)image {
self.imageView.image = image;
}
You would set up self.imageView to display the low-res image and then call loadImage: to load the high-res version.
Note that if you call this repeatedly before didLoadImageInBackground: gets called from earlier calls, you may cause the device to run out of memory. Or you might have the image from the first call take so much longer to load than image from the second call that didLoadImageInBackground: gets called for the second image before it gets called for the first. Fixing those issues is left as an exercise for the reader (or for another question).

Objective C: EXC_BAD_ACCESS when generating a UIImage

I have a view that generates an image based on a series of layers. I have images for the background, for the thumbnail, and finally for an overlay. Together, it makes one cohesive display.
It seems to work a dream, except for when it doesn't. For seemingly no reason, I get an EXC_BAD_ACCESS on the specified line below after it's generated somewhere between 8 and 20 images. I've run it through the memory leak tool and allocation tool, and it's not eating up tons of memory and it's not leaking. I'm totally stumped.
Here's the relevant code:
- (UIImage *)addLayer:(UIImage *)layer toImage:(UIImage *)background atPoint:(CGPoint)point {
CGSize size = CGSizeMake(240, 240);
UIGraphicsBeginImageContext(size);
[background drawAtPoint:CGPointMake(0, 0)]; // <--- error here
[layer drawAtPoint:point];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
// Build the layered image -- thingPage onto thingBackground,
// then the screenshot on that, then the thingTop on top of it all.
// thingBackground, thingPage and thingTop are all preloaded UIImages.
-(UIImage *)getImageForThing:(Thing *)t {
[self loadImageCacheIfNecessary];
if (!t.screenshot) {
return [UIImage imageNamed:#"NoPreview.png"];
} else {
UIImage *screenshot = t.screenshot;
UIImage *currentImage = [self addLayer:thingPage toImage:thingBackground atPoint:CGPointMake(0, 0)];
currentImage = [self addLayer:screenshot toImage:currentImage atPoint:CGPointMake(39, 59)];
currentImage = [self addLayer:thingTop toImage:currentImage atPoint:CGPointMake(0, 1)];
return currentImage;
}
}
I can't find anywhere that this is going wrong, and I've been tearing my hair out for a couple of hours on this. It's the final known bug in the system, so you can imagine how antsy I am to fix it! :-)
Thanks in advance for any help.
As to me, I always use -(void)drawInRect: instead of -(void)drawAtPoint:
CGRect rtDraw;
rtDraw.origin = CGPointZero;
rtDraw.size = size;
[background drawInRect:rtDraw];
[layer drawInRect:rtDraw];
And ....
The paint method with UIGraphicsBeginImageContext(size) and UIGraphicsEndImageContext() is not thread-safe.
Those functions will push or pop a context with stack struct, which is managed by system.
EXC_BAD_ACCESS is almost always due to accessing an object that has already been released. In your code this seems to be t.screenshot. Check creation (and retaining if it is an instance variable) of the object returned by Thing's screenshot property.
As it turns out, the error wasn't in the code I posted, it was in my caching of the thingBackground, thingPage and thingTop images. I wasn't retaining them. Here's the missing code, fixed:
-(void)loadImageCacheIfNecessary {
if (!folderBackground) {
thingBackground = [[UIImage imageNamed:#"ThingBack.png"] retain];
}
if (!folderPage) {
thingPage = [[UIImage imageNamed:#"ThingPage.png"] retain];
}
if (!folderTop) {
thingTop = [[UIImage imageNamed:#"ThingTop.png"] retain];
}
}
I will admit I'm still not comfortable with the whole retain/release/autorelease stuff in Objective C. Hopefully it'll sink in one day soon. :-)