i have two layers of UIImageView, upper one is partly transparent, second in is 'background'. I want to save them both like user see them from front into cameraRoll for user's use. The problem is writing it in way:
if(gridUpperLayer == transparent) {drawGridLowerLayer}
else {drawGridUpperLayer}
will be very slow (and i dont know how to implement it). Anybody has idea how to do it in faster way..? Best would be with example but i would be grateful for anything ^^
Cheers and thank you in advance!
You can do this by rendering the CALayer into an image for the UIView that contains both of the images. The following code would look like:
UIGraphicsBeginImageContext(containerView.frame.size);
[containerView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *anImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
//save anImage to disk
Related
In my project i need to draw 2D image in realtime corresponding with UIGestureRecognizer updates .
The image would be the same UIImage , drawing on various positions.
let arrayOfPositions = [pos1,pos2,pos3]
And i need to transfer the result image on MetalLayer into Single UIImage , the result image will have the same size as device's screen.
something similar to
let resultImage = UIGraphicsGetImageFromCurrentImageContext()
I'm new to Metal and after watching realm's video and apple documentation my sanity went to chaos . Most tutorials focus on 3D rendering which is beyond my need (and my knowledge)
If anyone would help me a simple code how to draw UIImage in to MetalLayer , then convert the whole into single UIImage as a result ? thanks
I'm trying to add a blur effect to a background view.
Here's my background view.
https://github.com/martinjuhasz/MJPopupViewController/blob/master/Source/MJPopupBackgroundView.m
I believe that the idea is to take a snapshot of the parent view and then add a blur effect to that image.
I've seen various approaches not sure what will work and what is the best approach.
Also I'm not sure where I'd create the snapshot.
The most common way is indeed probably just to take a snapshot and blur that.
You can take a snapshot by doing something like this:
+ (UIImage *) imageWithView:(UIView *)view
{
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0f);
[view drawViewHierarchyInRect:view.bounds afterScreenUpdates:NO];
UIImage * snapshotImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return snapshotImage;
}
Keep in mind this is a fast iOS7+ blurring method so if you want to support lower versions of iOS you will need to use a slower method, detailed in this answer.
There are a lot of ways to achieve blur, the 2 most popular are probably to use Apple's UIImageEffects WWDC sample code which can be found here, or to use GPUImage, which can be found here.
Ablow link points to present view and affect the background with blur effect
https://stackoverflow.com/a/52374977/5233180
I have several shinobicharts in my App that I want to print into a PDF file. Everything else, like normal views, labels and images work fine, even the grid, legend and gridlabels are displayed. The only thing missing are the series. So basically I get an empty chart printed into the PDF file.
I print the PDF as follows:
NSMutableData * pdfData=[NSMutableData data];
PDFPage1ViewController *pdf1 = [self.storyboard instantiateViewControllerWithIdentifier:#"PDF1"];
pdf1.array1 = array1;
pdf1.array2 = array2;
pdf1.array3 = array3;
pdf1.array4 = array4;
UIGraphicsBeginPDFContextToData(pdfData, CGRectZero,nil);
CGContextRef pdfContext=UIGraphicsGetCurrentContext();
UIGraphicsBeginPDFPage();
[pdf1.view.layer renderInContext:pdfContext];
UIGraphicsEndPDFContext();
The exact same code from PDF1PageViewController draws beautiful charts in a normal viewController, not missing the series.
The arrays contain the data which should be displayed.
[EDIT]
This code did it for me:
UIGraphicsBeginImageContextWithOptions(pdf1.view.bounds.size, NO, 0.0);
[pdf1.view drawViewHierarchyInRect:pdf1.view.bounds afterScreenUpdates:YES];
UIImage *pdf1Image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView *pdf1ImageView = [[UIImageView alloc] initWithImage:pdf1Image];
[pdf1ImageView.layer renderInContext:pdfContext];
Although the activity wheel stops spinning after drawViewHierarchyInRect and the label displaying the current page being rendered also stops updating. Anyone knows how to fix this?
The reason that you're having this problem is that the series part of the charts are rendered in openGLES, and therefore don't get rendered as part of renderInContext:.
You have a couple of options which you can investigate using. the first is the addition of some snapshotting methods on UIView in iOS7. If you're app can be restricted to iOS7 only, then snapshotViewAfterScreenUpdates: will return you a UIView which is a snapshot of the content. I think that the following (untested) code will work:
UIGraphicsBeginPDFPage();
UIView *pdfPage = [pd1.view snapshotViewAfterScreenUpdates:YES];
[pdfPage.layer renderInContext:pdfContext];
UIGraphicsEndPDFContext();
There are more details on this approach on the ShinobiControls blog at http://www.shinobicontrols.com/blog/posts/2014/02/24/taking-a-chart-snapshot-in-ios7
If restricting your app to iOS7 isn't an option then you can still achieve the result you want, but it is a little more complicated. Luckily, again, there is a blog post on the ShinobiControls blog (http://www.shinobicontrols.com/blog/posts/2012/03/26/taking-a-shinobichart-screenshot-from-your-app) which describes how to create a UIImage from a chart. This could easily be adapted to render into your PDF context, rather than the image context created in the post. There is an additional code snippet to accompany the post, available on github: https://github.com/ShinobiControls/charts-snippets/tree/master/iOS/objective-c/screenshot.
Hope this helps
sam
I have a custom UITableViewCell subclass which shows and image and a text over it.
The image is downloaded while the text is readily available at the time the table view cell is displayed.
From various places, I read that it is better to just have one view and draw stuff in the view's drawRect method to improve performance as compared to have multiple subviews (in this case a UIImageView view and 2 UILabel views)
I don't want to draw the image in the custom table view cell's drawRect because
the image will probably not be available the first time its called,
I don't want to draw the whole image everytime someone calls drawRect.
The image in the view should only be done when someone asks for the image to be displayed (example when the network operation completes and image is available to be rendered). The text however is drawn in the -drawRect method.
The problems:
I am not able to show the image on the screen once it is downloaded.
The code I am using currently is-
- (void)drawImageInView
{
//.. completion block after downloading from network
if (image) { // Image downloaded from the network
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
CGContextSetLineWidth(context, 1.0);
CGContextSetTextDrawingMode(context, kCGTextFill);
CGPoint posOnScreen = self.center;
CGContextDrawImage(context, CGRectMake(posOnScreen.x - image.size.width/2,
posOnScreen.y - image.size.height/2,
image.size.width,
image.size.height),
image .CGImage);
UIGraphicsEndImageContext();
}
}
I have also tried:
UIGraphicsBeginImageContext(rect.size);
[image drawInRect:rect];
UIGraphicsEndImageContext();
to no avail.
How can I make sure the text is drawn on the on top of the image when it is rendered. Should calling [self setNeedsDisplay] after UIGraphicsEndImageContext(); be enough to
ensure that the text is rendered on top of the image?
You're right on the fact that drawing text will make your application faster as there's no UILabel object overhead, but UIImageViews are highly optimized and you won't probably ever be able to draw images faster than this class. Therefore I highly recommend you do use UIImageViews to draw your images. Don't fall in the optimization pitfall: only optimize when you see that your application is not performing at it's max.
Once the image is downloaded, just set the imageView's image property to your image and you'll be done.
Notice that the stackoverflow page you linked to is almost four years old, and that question links to articles that are almost five years old. When those articles were written in 2008, the current device was an iPhone 3G, which was much slower (both CPU and GPU) and had much less RAM than the current devices in 2013. So the advice you read there isn't necessarily relevant today.
Anyway, don't worry about performance until you've measured it (presumably with the Time Profiler instrument) and found a problem. Just implement your interface in the simplest, most maintainable way you can. Then, if you find a problem, try something more complicated to fix it.
So: just use a UIImageView to display your image, and a UILabel to display your text. Then test to see if it's too slow.
If your testing shows that it's too slow, profile it. If you can't figure out how to profile it, or how to interpret the profiler output, or how to fix the problem, then come back and post a question, and include the profiler output.
Here's what I want to do:
Get some destination.
Render it in the maps into a view.
Turn that into an image I can then save and use as a background.
Another option would be to put a map view down, turn off all input and just paint on top of it. Basically asking for a way to rasterize the map view. Wondering if anyone has done this.
You can render any view into an image with something like this:
UIGraphicsBeginImageContextWithOptions(mapView.bounds.size, NO, 0.0f);
[mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *mapImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();