I have the following method to take a screenshot (UIImage) of a UIView which is far too slow
+ (UIImage *)imageWithView:(UIView *)view
{
CGSize size = view.bounds.size;
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
[view.layer renderInContext:context];
UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext()
return image;
}
On my iPad I now have an app that needs this method to make a copy of a view that is drag&dropped. This view is one with rounded corners and therefore is not opaque (which not makes a difference to if I would set the isOpaque param to YES I found out)...
Also the view that is screenshotted contains a UITableView with quite some complex entries in it...
Do you have any suggestions on how I can improve the speed of the screenshotting. Right now, for a bit bigger tableview (maybe 20 entries) it takes about 1 second (!!!)
And the view is already on screen, rendered correctly... so I just need the Pixels to but into an UIImageView...
I need to support iOS 6+.
I use this same code to take a screenshot of a really complex views. I think your bottleneck is using a big image for the drag&drop. Maybe you can resize the UIImage.
In my case the performance in a iPad2 is about 100ms for screenshot.
Related
I'm trying to save the currently shown views on my iOS device for a certain app, and this is working properly. But I've got a problem as soon as I'm trying to save a UIImageView in Landscape orientation.
See the following image that describes my problem:
I'm using Auto layout for this app, and it runs on both iPhone and iPad. It seems like the ImageView is always saved as shown in portrait mode, and I'm a little bit stuck right now.
This is the code I use:
CGSize frameSize = self.view.frame.size;
if (UIInterfaceOrientationIsLandscape(self.interfaceOrientation)) {
frameSize = CGSizeMake(self.view.frame.size.height, self.view.frame.size.width);
}
UIGraphicsBeginImageContextWithOptions(frameSize, NO, 0.0);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGFloat scale = CGRectGetWidth(self.view.frame) / CGRectGetWidth(self.view.bounds);
CGContextScaleCTM(ctx, scale, scale);
[self.view.layer renderInContext:ctx];
[self.delegate photoSaved:UIGraphicsGetImageFromCurrentImageContext()];
UIGraphicsEndImageContext();
Looking forward to your help!
I still have no idea what your exact issue is but using your screenshot code makes a bit strange image (not rotated or anything though, just too small). Can you try this code instead please.
+ (UIImage *)imageFromView:(UIView *)view {
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, .0f);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img;
}
Other then that you must understand there is a huge difference between UIImage and CGImage as the UIImage includes the orientation while CGImage does not. When dealing with image transformations it is usually with the CGImage and getting its width or height will discard the orientation. That means a CGImage will have flipped dimensions when its orientation is not up (UIImageOrientationUp). But usually when dealing with such images you create a CGImage from the context and then use [UIImage imageWithCGImage:ref scale:1.0f orientation:originalOrientation]. Only if you wish to explicitly rotate the image so it has no orientation (being UIImageOrientationUp) you need to rotate and translate the image and draw it onto the context.
Anyway, this orientation issues are quite fixed by now, UIImagePNGRepresentation respects the orientation and you have an image constructor from the CGImage already written above which is what used to be missing in the past if I remember correctly.
I try to take screenshot of uiwebview and send it with observer to another UIImageView in another class.
I using this method to take screenshot:
-(UIImage*)takeScreenshoot{
#autoreleasepool {
UIGraphicsBeginImageContext(CGSizeMake(self.view.frame.size.width,self.view.frame.size.height));
CGContextRef context = UIGraphicsGetCurrentContext();
[self.webPage.layer renderInContext:context];
UIImage *__weak screenShot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return screenShot;
}
}
But then I have problem. Everytime I take screenshot with this method, memory rate grows about 10-15mb and it's not realising it. And if I take screenshot in every webviewdidfinishload, you can imagine how much it can take memory!
How can I fix that issue?
If possible try to use [UIScreen snapshotViewAfterScreenUpdates] which returns UIView .
This is the snapshot of currently displayed content (snapshot of app).
Even apple also says " this method is faster than trying to render the contents of the screen into a bitmap image yourself."
According to your code, you are passing this bitmap image to just display in some other UIImageView. so i think using UIScreen method is appropriate here.
To display UIWebView part only->
Create another UIView instance. Set its frame to the frame of your webView.
Now add this screenShot view as subView to createdView and set its frame such that webView portion will be displayed.
Try calling CGContextRelease(context); after you have got your screen shot.
Or as #Greg said, remove the line and use UIGraphicsGetCurrentContext() directly
I am trying to implement sharing app with facebook.
I used this code to take the screenshot:
CGSize imageSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height);
UIGraphicsBeginImageContext(imageSize);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
It works great on iOS 6, but in iOS 7 the image looks very bad.
I used this answer: iOS: what's the fastest, most performant way to make a screenshot programmatically?
for trying to fix it, and it helped, still the screenshot looks bad.
The screen gets another color, and some objects (like labels) aren't showing on the image taken.
Any help?
----Update----
I managed to solve the most objects, by change them to retain instead of weak. My main problem remained my tableview, that shown as a big white block (It supposed to be transparent, with labels with white text, so all we see is white cells). I did try to define the table background as clearcolor,not helps..
----Last Update---
There are wonderful answers here that not really regarding to my issue.. I wanted to make it work on device that runs with iOS7 but without using iOS7 SDK, since it takes to much effort to switch the project SDK in this point, when the project is almost done.
Anyway, I added the peace of code that finally solved my issue:
This change simply solve the problem:
UIGraphicsBeginImageContextWithOptions(imageSize, NO , 0.0f);
instead of:
UIGraphicsBeginImageContext(imageSize);
New API has been added since iOS 7, that should provide efficient way of getting snapshot
snapshotViewAfterScreenUpdates: renders the view into a UIView with unmodifiable content
resizableSnapshotViewFromRect:afterScreenUpdates:withCapInsets : same thing, but with resizable insets
drawViewHierarchyInRect:afterScreenUpdates: : same thing if you need all subviews to be drawn too (like labels, buttons...)
You can use the UIView returned for any UI effect, or render in into an image like you did if you need to export.
I don't know how good this new method performs VS the one you provided (although I remember Apple engineers saying this new API was more efficient)
you can try this
- (UIImage *) screenshot {
UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, NO, [UIScreen mainScreen].scale);
[self.view drawViewHierarchyInRect:self.view.bounds afterScreenUpdates:YES];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
in iOS 8 : this is how i am doing to get ScreenShot
just added one UIImageView and Method to take screenshot in .h file
#property (weak, nonatomic) IBOutlet UIImageView *imageView;
-(IBAction)takeSnapShot:(id)sender;
2 added code snip for taking screen shot and set on UIImageView in .m file
- (IBAction)takeSnapShot:(id)sender
{
UIGraphicsBeginImageContext(self.view.bounds.size);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *snapShotImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
imageView.image = snapShotImage;
}
below is the output i got.
On iOS7 you can have glitches if you use
[view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES]
during ongoing animation. Set afterScreenUpdates = NO to get rid of glitches.
Make sure that opaque is set to NO
I'm searching a way to draw stretchable image as background of my custom cell background view. I would like to use drawRect method and draw an image stretched exactly as it would be stretched with stretchableImageWithLeftCapWidth in a UIImageView... how can i continue this code to make it happen ?
- (void)drawRect:(CGRect)rect{
CGContextRef context = UIGraphicsGetCurrentContext();
UIImage *bgImg =[[UIImage imageNamed:#"bg_table_top"]stretchableImageWithLeftCapWidth:3 topCapHeight:0];
//How to draw the image stretched as the self.bounds size ?
....
}
Any reason not to let UIImageView do this? (Include one as a child of your custom cell.) It's true that reducing child views can be a performance improvement in tables, but UIImageView is also pretty good at getting good performance when drawing images.
My guess is otherwise you're going to have to do multiple draw calls, in order to get the ends and middle drawn correctly.
I've got two UIImageView: the first one is laying on the top of the other (eg. an overlay).
I want now to take a screenshot of the whole thing.
Note that before that step, I allow the user to change the overlay by panning,scaling and ROTATING it, so I must keep track of his editing.
So, here's the homework:
rotating the context basing on the view's transform rotation value
positioning on the origin, where the user finished to pan the overlay
calculate the size of the overlay view (it's always a rectangle, however!)
I'm gonna merge them inside a similar piece of code:
UIGraphicsBeginImageContext...
...
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
but... what does "best fit" instead of the "..."?
Example code is well accepted!
Thanks
UIGraphicsBeginImageContext(firstImage.size);
[firstImage drawAtPoint:CGPointMake(0,0)];
[secondImage drawAtPoint:CGPointMake(0,0)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();