I want to create a snapshot image for a UIView, I used to use renderInRect, but it is slow, and I found that drawViewHierarchyInRect is a newer API since iOS 7, so I want to try it.
I write below code, but it never create a valid image, just a blank image.
-(void)drawRect:(CGRect)rect {
UIGraphicsBeginImageContextWithOptions(_mapView.bounds.size, _mapView.opaque, [[UIScreen mainScreen] scale]);
CGContextRef context = UIGraphicsGetCurrentContext();
// Used to use renderInContext, but it's slow
// [mapView.layer renderInContext:context];
[_mapView drawViewHierarchyInRect:_mapView.bounds afterScreenUpdates:YES];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.thumbImageView = [[UIImageView alloc] initWithImage:image];
[self addSubview:self.thumbImageView];
}
The -drawViewHierarchyInRect:afterScreenUpdates:, which lets you render a snapshot of the complete view hierarchy as visible onscreen into a bitmap context.
renderInContext: renders directly from a CALayer's render tree to valid Core Graphics context.
If you want to render the view to a UIImage rather than having it on the View Hierarchy, you should using renderInContext.
Related
I'm trying in my app to take a screenshot of the current screen contents, where my TilingView (based on CATiledLayers) displays a number of transparent large tiled images.
Also I added some subViews to the TilingView, which are magically captured in the screenshot, however the underlying contents of the TilingView is not captured!??
The following code-snippets takes a snapshot of the visible screen, which seems to work well for a NON CATiledLayer based view-hierarchy, but unfortunately doesn't work for my setup. Even if I pass the topmost superview of the TilingView (being the actual UIViewController.view), I see only in my snapshot the StatusBar, NavigationBar, the TilingViews subViews and the TabBar, but again NOT the TilingViews contents.
- (UIImage*)captureView:(UIView *)viewToCapture {
CGRect rect = [[UIScreen mainScreen] bounds];
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
[viewToCapture.layer renderInContext:context];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
Does anybody know or see here what I'm missing? Do I need to delve deeper into the CG-related display stack with some, for me, unknown CG-API calls? Thanks in advance.
By searching some more in StackOverflow I've found code which seems to do what I wanted. Basically I need to change the above method into:
- (UIImage*)captureView:(UIView*)viewToCapture {
UIGraphicsBeginImageContextWithOptions(viewToCapture.bounds.size, NO, [UIScreen mainScreen].scale);
[viewToCapture drawViewHierarchyInRect:viewToCapture.bounds afterScreenUpdates:YES];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
Thanks go to the question/answer at: How to get a screenshot of a view containing GPUImageView?
I am currently using:
CGRect rect = [self.view bounds];
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0f);
CGContextRef context = UIGraphicsGetCurrentContext();
[self.view.layer renderInContext:context];
UIImage *capturedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
This retrieves a screen shot of the current view once a UITabBarItem is selected. The problem is, this will always capture the view of the current view the user is active on before switching to the next view.
To better understand this. I have a UITabBarController that manages my navigation for my app. The walk in View controller is a table that I want to always capture a picture of when the user selects the Share UITabBarItem on the navigation. So I have this linked to a method that checks to see if Share has been clicked and creates an image of the current view as shown above.
My roadblock is, how can I capture an image of that first view(walk in view) every time no matter what view the user is currently on?
I am handling my capturing functionality within a custom class that initates the UITabBarController
Suggestions thoughts?
Will this help you?
CGRect rect = [yourTabController.viewControllers[walkInViewIndex].view bounds];
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0f);
CGContextRef context = UIGraphicsGetCurrentContext();
[yourTabController.viewControllers[walkInViewIndex].view.layer renderInContext:context];
UIImage *capturedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[self.view.layer renderInContext:context];
This explicitly takes a snapshot of the current view (self.view). What you'll want to do is more or less the same procedure, but by specifying your walk in view instead:
[self.walkingController.view.layer renderInContext:context];
I've searched a lot but only found two methods to take screen shot of UIView.
first renderInContext:
I've used it in a way
CGContextRef context = [self createBitmapContextOfSize:CGSizeMake(nImageWidth, nImageHeight)];
CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, nImageHeight);
CGContextConcatCTM(context, flipVertical);
[self.layer setBackgroundColor:[UIColor clearColor].CGColor];
[self.layer renderInContext:context];
CGImageRef cgImage = CGBitmapContextCreateImage(context);
UIImage* background = [UIImage imageWithCGImage: cgImage];
CGImageRelease(cgImage);
Second drawViewHierarchyInRect: which I've used as
UIImage *background = nil;
UIGraphicsBeginImageContextWithOptions (self.bounds.size, NO, self.window.screen.scale);
if ([self respondsToSelector:#selector(drawViewHierarchyInRect:afterScreenUpdates:)])
{
[self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES];
}
background = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
I know that the second one is faster than first and it work for me for iPhone because the view has low size. but when I capturing from iPad the video become jerky.
Can Any body tell me faster way of taking screen shot.
any help would be highly appreciated
Regarding performance, the Apple Docs state the following:
In addition to -drawViewHierarchyInRect:afterScreenUpdates:, UIView
now provides another two snapshot related methods,
-snapshotViewAfterScreenUpdates: and -resizableSnapshotViewFromRect:afterScreenUpdates:withCapInsets:. UIScreen also has -snapshotViewAfterScreenUpdates:.
Unlike UIView's -drawViewHierarchyInRect:afterScreenUpdates:, these
methods return a UIView object. If you are looking for a new snapshot
view, use one of
these methods. It will be more efficient than calling
-drawViewHierarchyInRect:afterScreenUpdates: to render the view contents into a bitmap image yourself. You can use the returned view
as a visual stand-in for the current view/screen in your app. For
example, you might use a snapshot view for animations where updating a
large view hierarchy might be expensive.
There is a third method for taking a snapshot that is much much quicker than either of these but it returns a UIView.
- (UIView *)snapshotViewAfterScreenUpdates:(BOOL)afterUpdates
If you are just using the snapshot to place as a background "image" etc... then I'd use this instead.
However, this is only available for iOS8.
To use it just do...
UIView *snapshotView = [someView snapshotViewAfterScreenUpdates:YES];
This Method will return you A snapshot images of particular view
-(UIImage *)createSnapShotImagesFromUIview
{
UIGraphicsBeginImageContext(CGSizeMake(view.frame.size.width,view.frame.size.height));
CGContextRef context = UIGraphicsGetCurrentContext();
[mapView.layer renderInContext:context];
UIImage *img_screenShot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img_screenShot;
}
I have been trying to do this since forever. I have a camera overlay. I want to get my final image to be the part of the image viewable from the in-built camera.
What I did was make CGRect with dimensions equal to the square in the camera. Then I tried cropping it using this function.
- (UIImage *)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect
{
CGImageRef imageRef = CGImageCreateWithImageInRect([imageToCrop CGImage], rect);
UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return croppedImage;
}
I called it like this
CGRect rect = CGRectMake(10, 72, 300, 300);
UIImage *realImage = [self imageByCropping:[self.capturedImages objectAtIndex:0] toRect:rect];
What I get is a bad quality image with the wrong orientation.
::EDIT::
With Nitin's answer I can crop the correct part of the screen but the problem is it crops the view that follows the camera view, 'the confirmation view'. I suspect this is because Nitin's code uses
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
and because the ViewController in which all this is happening because the View Controller for the Confirmation View is the Controller in which this code is being executed. I will try to explain this with a small map
CameraOverlay.xib(it uses this xib to create an overlay) <===== CameraOverlayViewController ---------> ConfirmationView
So when first the ViewController is evoked(button on Tab bar), it opens the camera(UIImagePickerController) with an overlay over it. Then once user clicks an image, the image is shown on the ConfirmationView.
What I think is happening is when
UIGraphicsBeginImageContextWithOptions(self.view.frame.size, YES, 1.0);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
these lines are being executed, the View at that time is ConfirmationView.
Note: I call the function in
(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info method.
Refer Drawing and printing Guide.
The default coordinate system is different between CoreGraphics and UIKit. I think your issue is because of this fact.
Using these may help you solve the issue
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context , 0.0, rect.size.height);
CGContextScaleCTM(context , 1.0, -1.0);
I'm trying to make a transition between two ViewControllers. My Transition class has a property for the destination view controller. When I try to get a screenshot of the destination's view, I use this method:
+ (UIImage *)renderImageFromView:(UIView *)view withRect:(CGRect)frame {
// Create a new context the size of the frame
UIGraphicsBeginImageContextWithOptions(frame.size, YES, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
// Render the view
[view.layer renderInContext:context];
// Get the image from the context
UIImage *renderedImage = UIGraphicsGetImageFromCurrentImageContext();
// Cleanup the context you created
UIGraphicsEndImageContext();
return renderedImage;
}
So when I want the image, I'll do this:
UIImage *image = [UIImage renderImageFromView:destinationController.view withRect:destinationController.view.bounds];
I tried it on a blank UIViewController with an orange background color and a label. I get the orange background color, but I do not get the label that was created in IB. Is there a way to get a proper screenshot of the new view I plan on showing? Thanks!
You need to make sure the view's layer is drawn to first. Calling renderInContext on a CALayer will only recursively call additional child CALayers. You need your child UIViews to draw themselves, not just using the CALayer.
Try calling
[view drawrect:frame];
instead of
[view.layer renderInContext:context];
As long as you have an open graphics context(which you do at that point), drawrect should draw directly into that.