UIImage problem - iphone

Question

I am loading the images of size 450KB in UIImage view and then adding it to UIscrollview. while am scrolling the 30 images continously,its getting crashed.. what may be the reason..is this memory leak issue...or image size is the problem...? thanks in advance..
here is my code ..
#try{
NSAutoreleasePool *pool;
pool = [[NSAutoreleasePool alloc] init];
//NSArray *array = [global_ContentString componentsSeparatedByString:#"###"];
NSArray *array1 = [catalogURL componentsSeparatedByString:#"&"];
//**NSLog(#"array1****** = %#",array1);
NSLog(#"loading catalog image(method: loadCatalogImage).......%#%#",baseURL, [[[array1 objectAtIndex:0] componentsSeparatedByString:#"##"] objectAtIndex:0]);
//NSLog(#"baseURL = %#",baseURL);
NSLog(#"loading catalog image.......%#%#",baseURL, [[[array1 objectAtIndex:0] componentsSeparatedByString:#"##"] objectAtIndex:0]);
zoomedImageURL = [NSString stringWithFormat:#"%#%#", baseURL, [[[array1 objectAtIndex:0] componentsSeparatedByString:#"##"] objectAtIndex:1]];
[zoomedImageURL retain];
NSLog(#"aaaaaaaaaaaaaa = %#",zoomedImageURL);
//UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#%#",baseURL, [[[array1 objectAtIndex:0] componentsSeparatedByString:#"##"] objectAtIndex:0]]]]];
UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",zoomedImageURL]]]];
imgView.contentMode = UIViewContentModeScaleAspectFit;
imgView.image = img;//[GPSTripTracking generatePhotoThumbnail:img:109];
[pool release];
[global_imgProgress stopAnimating];
}
#catch (NSException *e) {
[global_imgProgress stopAnimating];
NSLog(#"Exception....");
}
#finally {
}
am releasing my imgView in dealloc method..
i imlemented the following code in "scrollviewdidscroll"
- (void)scrollViewDidScroll:(UIScrollView *)sender {
// We don't want a "feedback loop" between the UIPageControl and the scroll delegate in
// which a scroll event generated from the user hitting the page control triggers updates from
// the delegate method. We use a boolean to disable the delegate logic when the page control is used.
if (pageControlUsed) {
// do nothing - the scroll was initiated from the page control, not the user dragging
//pageText.text = [NSString stringWithFormat:#"%d/%d", (pageControl.currentPage +1), pageControl.numberOfPages];
pageText.text = [NSString stringWithFormat:#"%d/%d", (pageControl.currentPage ), pageControl.numberOfPages];
//NSLog(#"not scrollling page....");
return;
}
// Switch the indicator when more than 50% of the previous/next page is visible
CGFloat pageWidth = scrollView.frame.size.width;
int page = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
pageControl.currentPage = page;
// load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
[self loadScrollViewWithPage:page - 1];
[self loadScrollViewWithPage:page];
[self loadScrollViewWithPage:page + 1];
//NSLog(#"scrolling page....%d", page);
// A possible optimization would be to unload the views+controllers which are no longer visible
}
and my code for " loadScrollViewWithPage" is
- (void)loadScrollViewWithPage:(int)page
{
//page--;
if (page < 0) return;
if (page >= numberOfPages) return;
if(!isViewCatalog && searchId == 1)
{
//NSLog(#"curre page = %d",pageControl.currentPage);
NSArray *array1 = [global_ContentString componentsSeparatedByString:#"###"];
if(searchInCatalogFlag == 1)
{
pageControl.currentPage=0;
NSArray *urlArray = [[array1 objectAtIndex:pageControl.currentPage] componentsSeparatedByString:#"##"];
//NSLog(#"url array** = %#",urlArray);
headerText.text = [NSString stringWithString:[urlArray objectAtIndex:0]];
pageText.text = [NSString stringWithFormat:#"%d/%d", pageControl.currentPage, (pageControl.numberOfPages - 1)];
}
else
{
NSArray *urlArray = [[array1 objectAtIndex:pageControl.currentPage] componentsSeparatedByString:#"##"];
//NSLog(#"url array** = %#",urlArray);
headerText.text = [NSString stringWithString:[urlArray objectAtIndex:0]];
pageText.text = [NSString stringWithFormat:#"%d/%d", pageControl.currentPage, (pageControl.numberOfPages - 1)];
}
if(page == selectedPage && ![global_imgProgress isAnimating])
[global_imgProgress startAnimating];
}
else
{
headerText.text = [NSString stringWithString:global_SelectedCatalogName];
pageText.text = [NSString stringWithFormat:#"%d/%d", (pageControl.currentPage + 1), (pageControl.numberOfPages - 1)];
if(page == selectedPage + 1 && ![global_imgProgress isAnimating] )
[global_imgProgress startAnimating];
// NSLog(#"header text = %#", headerText.text);
//headerText.text = [NSString stringWithString:[urlArray objectAtIndex:0]];
}
FullPageView *controller = [viewControllers objectAtIndex:page];
if ((NSNull *)controller == [NSNull null] ) {
//NSLog(#"Loading page =========== %d, %d", page, selectedPage);
//voucherPageNo = page;
//[voucherImage retain];
if(universalApp==2)
{
controller = [[FullPageView alloc] initWithNibName:#"FullPageView_iphone" bundle:nil];//:page];
[controller.view setFrame:CGRectMake(0, 0, 320,332)];
}
else
{
controller = [[FullPageView alloc] initWithNibName:#"FullPageView" bundle:nil];//:page];
[controller.view setFrame:CGRectMake(0, 192, 768, 691)];
}
//[controller.view setFrame:CGRectMake(0, 0, 320,480)];
//[controller.view setFrame:CGRectMake(0, 192, 768, 691)];
if((!isViewCatalog && searchId < 2 && searchInCatalogFlag == 0))// || searchInCatalogFlag == 1)
{
// NSLog(#">>>>>>>>>>>>>>>>>> LOADING IMAGE >>>>>>>>>>>>>>>>>>>>");
[controller setPageNo:page];
// if(page >= selectedPage - 1)
[NSThread detachNewThreadSelector:#selector(loadImage) toTarget:controller withObject:nil];
}
else //if((page >= (selectedPage - 1) && page <= (selectedPage + 1)) || !isFirstTimeLoading)
{
NSLog(#"Loading CATALOG IMAGE = %d, %d, %#", page, selectedPage, (isFirstTimeLoading ?#"YES" : #"NO"));
[controller setCatalogURL:[NSString stringWithFormat:#"%#", [catalogArray objectAtIndex:page+(searchId< 2 && !isViewCatalog && searchInCatalogFlag == 0?0:1)]]];
NSLog(#"loading image ipad= %#", [catalogArray objectAtIndex:page+(searchId< 2 && !isViewCatalog && searchInCatalogFlag == 0?0:1)]);
// if(page >= selectedPage - 1)
[NSThread detachNewThreadSelector:#selector(loadCatalogImage) toTarget:controller withObject:nil];
// if(page == (selectedPage + 1))
//isFirstTimeLoading = NO;
}
[viewControllers replaceObjectAtIndex:page withObject:controller];
[controller release];
}
// add the controller's view to the scroll view
if (nil == controller.view.superview)
{
// NSLog(#"Voucher view addead at page..... %d", page);
CGRect frame = scrollView.frame;
frame.origin.x = frame.size.width * page;
frame.origin.y = 0;
controller.view.frame = frame;
// NSLog(#">>>>>>>>> %f, %f", frame.size.width, frame.origin.x);
[scrollView addSubview:controller.view];
}
//if(page == pageControl.currentPage)
//[imgProgress startAnimating];
//else
//pageControlUsed = YES;
}
where wil be the problem..?

Answer 1

450KB is the compressed image size. When an image is loaded into memory, it is uncompressed.
A rule of thumb for working out how much memory an uncompressed image will occupy is:
width * height * 4
With 30 images it is very likely that you're running out of memory.
You should write your code to only keep images in memory if they are visible on screen.

Answer 2

It very likely that your program gets terminated by iOS because it consumes too much memory. Start it from XCode and look at the console - it will probably print that it receives memory warnings.
You will have to load the images on demand, i.e. only when the user gets close to seeing them, and you will have to release the ones that move out of view again. To that end, implement the
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
delegate method, look at the scroll view's content offset and load/release the appropriate images. Alternatively, you can choose to not release them there but instead wait for a memory warning to do so. To do so, implement the
- (void)didReceiveMemoryWarning
method in your view controller.

Answer 3

This might be the issue of memory leaks.
Try to replace this line
UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",zoomedImageURL]]]]
and use this
UIImage *img = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",zoomedImageURL]]]];
<<<<<YOUR CODE>>>>
[img release];
I hope this helps