I am loading a ppt file from email using UIWebView and converting the ppt pages to images using renderInContext: api in a do while loop on main thread.
It is working fine when I load small ppt files having less than 50 slides. My app is crashing when I load 100 page ppt documents. The crash is happening exactly 83rd time at renderInContext: API (render UILayer from UIWebview).
Below is the piece of code I am using in ARC application.
do
{
@autoreleasepool
{
NSLog(@"Image Index: %d",i);
UIGraphicsBeginImageContext(CGSizeMake(768.0f, 576.0f));
CGContextRef ctxCurrentGraphics = UIGraphicsGetCurrentContext();
[webView.layer renderInContext:ctxCurrentGraphics];
CGContextSetInterpolationQuality(ctxCurrentGraphics, kCGInterpolationHigh);
CGContextSetRenderingIntent(ctxCurrentGraphics, kCGRenderingIntentDefault);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
/******* Each snap shot been inserted to db before new snapshot created ********/
if (image != nil)
{
[[DataManager instance] insertImportedImageToDb:image importFileName:filename ...];
slideID++;
seqID++;
}
[webView.scrollView scrollRectToVisible:CGRectMake(0.0f, (i * 581.3) , webView.bounds.size.width, webView.bounds.size.height) animated:NO];
scrolloffset = scrolloffset + 581.3;
i++;
/***** check if ppt contains only one page ****/
if (webView.scrollView.contentSize.height == 1004.0 || webView.scrollView.contentSize.height == 1005.0)
{
break;
}
image = nil;
}
}
while (scrolloffset <= webView.scrollView.contentSize.height);
The app is crashing only on device (iOS6). I tried all alternatives which I find in Stack Overflow like clearing context, usage of @autoreleasepool etc.
Is there any way I can optimize the memory usage or is there any alternative to renderInContext: API where it seems this api has memory leak?
Edit1: Most of the time application received 'Low Memory warnings' but twice I see the below crash log:
Last Exception Backtrace:
0 CoreFoundation 0x316aa29e 0x315e8000 + 795294
1 libobjc.A.dylib 0x3954e97a 0x39546000 + 35194
2 CoreFoundation 0x316aa1c0 0x315e8000 + 795072
3 UIKit 0x3389dd5a 0x334af000 + 4123994
4 MyApplication 0x000c590c 0xa3000 + 141580
5 MyApplication 0x000c4d26 0xa3000 + 138534
6 Foundation 0x31fc1f4e 0x31f10000 + 728910
7 CoreFoundation 0x3167f5da 0x315e8000 + 619994
8 CoreFoundation 0x3167f28c 0x315e8000 + 619148
9 CoreFoundation 0x3167defc 0x315e8000 + 614140
10 CoreFoundation 0x315f0eb8 0x315e8000 + 36536
11 CoreFoundation 0x315f0d44 0x315e8000 + 36164
12 GraphicsServices 0x351a52e6 0x351a0000 + 21222
13 UIKit 0x335062fc 0x334af000 + 357116
14 MyApplication 0x000a8c60 0xa3000 + 23648
15 libdyld.dylib 0x39985b1c 0x39984000 + 6940
The root cause of the issue is recursively capturing images from webview where renderInContext: is used to capture.
The problem happened only after 83 image captures (84th iteration in for loop) and hence i felt there is huge memory leak.
Not sure this is optimistic solution for this problem. But I managed to solve using below steps..
(1) renderInContext: is not releasing the graphics context immediately and hence accumulating memory and hence low memory warnings. Solution i tried is keep the entire function under @autorelease and just delay capturing next image by 1 millisecond which is negligible in terms of performance.
(2) Avoided using forloop and storing images in a mutable array. This also saved some memory. This reduces heap memory usage as well.
Hope this helps somebody..