I'm drawing beziers and rather than memorize every bezier ever and re-draw it every frame, I'm occasionally taking a picture of the image with:
+ (UIImage *) imageWithView:(UIView *)view: (CGRect)theBounds
{
UIGraphicsBeginImageContextWithOptions(theBounds.size, NO, 0.0);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img;
}
Then I draw the image at the beginning of every drawRect, add new paths as they come in, occasionally take another picture, and repeat.
Is there a better way? It's working but I feels 'stupid.'
Ahaaa layer context.
That's all you had to say.
http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Reference/CGLayer/Reference/reference.html
BTW this is better, although I disagree with the phrase "non destructive." I wish I had found the below at the start of my project, but I never would have searched for "Non destructive." Although, who would ever search for "Cumulatively?" lol me no smartest
UIView: how to do non-destructive drawing?
Related
I followed #Rob answer and its drawn as I want...but when I saved this image....stroke not transparent anymore
Objective-C How to avoid drawing on same color image having stroke color of UIBezierPath
For save image I written this code
-(void)saveImage {
UIGraphicsBeginImageContextWithOptions(self.upperImageView.bounds.size, NO, 0);
if ([self.upperImageView respondsToSelector:#selector(drawViewHierarchyInRect:afterScreenUpdates:)])
[self.upperImageView drawViewHierarchyInRect:self.upperImageView.bounds afterScreenUpdates:YES]; // iOS7+
else
[self.upperImageView.layer renderInContext:UIGraphicsGetCurrentContext()]; // pre iOS7
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndPDFContext();
UIImageWriteToSavedPhotosAlbum(self.upperImageView.image, self,#selector(image:didFinishSavingWithError:contextInfo:), nil);
}
You are either setting the alpha of the image view with the paths to 1.0 somewhere, or you are using something that doesn't permit transparencies (e.g. UIGraphicsBeginImageContextWithOptions with YES for the opaque parameter, or staging the image in a format that doesn't preserve alpha, such as JPEG).
A few additional thoughts:
I notice that you're only drawing upperImageView. If you want the composite image, you need to draw both. Or are you only trying to save one of the image views?
(For those unfamiliar with that other question, the entire point was how to draw multiple paths over an image, and have the full set of those paths with the same reduced alpha, rather than having the intersection of paths lead to some additive behavior. This was accomplished by having two separate image views, one for the underlying image, and one for the drawn paths. The key to the answer to that question was that one should draw the paths at 100% alpha, but to add that as a layer to a view that, itself, has a reduced alpha.)
What is the alpha of the image view upon which you are drawing.
NB: In the answer to that other question, when saving a temporary copy of the combined paths. we had to temporarily set the alpha to 1.0. But when saving the final result here, we want to keep the "path" image view's alpha at its reduced value.
Unrelated, but you faithfully transcribed a typo (since fixed) in my original example where I accidentally called UIGraphicsEndPDFContext rather than UIGraphicsEndImageContext. You should use the latter.
So, considering two image views, one with the photograph and one with the drawn path, called imageImageView (with alpha of 1.0) and pathsImageView (with alpha of 0.5), respectively, I can save the snapshot like so:
- (void)saveSnapshot {
CGRect rect = self.pathsImageView.bounds;
UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
if ([self.pathsImageView respondsToSelector:#selector(drawViewHierarchyInRect:afterScreenUpdates:)]) {
[self.imageImageView drawViewHierarchyInRect:rect afterScreenUpdates:YES]; // iOS7+
[self.pathsImageView drawViewHierarchyInRect:rect afterScreenUpdates:YES];
} else {
[self.imageImageView.layer renderInContext:UIGraphicsGetCurrentContext()]; // pre iOS7
[self.pathsImageView.layer renderInContext:UIGraphicsGetCurrentContext()];
}
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(image, self, #selector(image:didFinishSavingWithError:contextInfo:), nil);
}
When I did that, the resulting composite image was in my photo album:
The images that goes through here are PNGs of different shapes with a transparent background. In addition to merging them (which works fine), I'd like to give the new image a couple of pixels thick outline. But I can't seem to manage that.
(So just to clarify, I'm after an outline around the actual shapes in the context, not a rectangle around the entire image.)
+ (UIImage *)mergeBackgroundImage:(UIImage *)backgroundImage withOverlayingImage:(UIImage *)overlayImage{
UIGraphicsBeginImageContextWithOptions(backgroundImage.size, NO, backgroundImage.scale);
[backgroundImage drawInRect:CGRectMake(0, 0, backgroundImage.size.width, backgroundImage.size.height)];
[overlayImage drawInRect:CGRectMake(backgroundImage.size.width - overlayImage.size.width, backgroundImage.size.height - overlayImage.size.height, overlayImage.size.width, overlayImage.size.height)];
//Add stroke.
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
Thanks for your time!
Markus
If you make a CALayer who's backing is set to a CGImage of your image, you can then use it as a masking layer for your layer that requires an outline1. And once you've done that, you can render your layer into another context, and then get another UIImage from that.
// edit: Something like what's describe in this answer.
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.
I want to capture screen of my view from my iPhone app. I have white background view and on that I draw a lines on that view's layer using this method .
- (void)draw {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
if (self.fillColor) {
[self.fillColor setFill];
[self.path fill];
}
if (self.strokeColor) {
[self.strokeColor setStroke];
[self.path stroke];
}
CGContextRestoreGState(context);
}
- (void)drawRect:(CGRect)rect {
// Drawing code.
for (<Drawable> d in drawables) {
[d draw];
}
[delegate drawTemporary];
}
I have use delegate methods to draw lines on layer.
This is the project link from where I get help for this.
https://github.com/search?q=dudel&type=Everything&repo=&langOverride=&start_value=1
Now when I use the following context methods to save the drawing only I successfully save it without that white background.
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
But When I use the following method of Bezier Pathe I cannot save the drawing without its white background,It saves the whole screen i.e. that drawing and its background.
UIGraphicsBeginImageContext(self.view.bounds.size);
[dudelView.layer renderInContext:UIGraphicsGetCurrentContext()];
//UIImage *finishedPic = UIGraphicsGetImageFromCurrentImageContext();
So can anybody help me how can I save the drawing only here in this app.
(You've tagged this as MapKit related, but make no mention of MapKit.)
Why don't you just split your drawing sequence into three chunks?
Draw your paths into an image context and get a UIImage, as you described.
Draw a background color.
Draw the UIImage.
Then you can use the UIImage for your "screenshot" as well.
I should also note that if the only thing you don't want in your captured UIImage is the background color, you are better off creating a UIImageView, setting its background color (-setBackgroundColor:), and setting its image to be your UIImage.
UIImageView internally has a number of optimizations that allow it to display graphics with much higher performance than you can get with a custom -drawRect: implementation.
Why don't you just save the drawables array? Those are all the drawings without the underlying image :)
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();