i would like to draw a border / shadow around a uiscrollview, i know that i could get there with an additional view or scrollview but dont like the handling an drawbacks but i heard that there should be a possibility to dirctly draw a border to a scrollview and that is what i would prefer.
I am quiet new to iphone developement,any answer would helpful.
If you use the layer property of your scroll view (or any UIView) you can easily get a solid border...
#import <QuartzCore/QuartzCore.h>
...
myView.layer.borderWidth = 2;
myView.layer.borderColor = [UIColor blackColor].CGColor;
You can also use the layer to apply real-time shadows by setting the layer.shadow* properties, but performance can be slow with this technique, so I generally prefer to use the following more complex, but more performant technique. You can create a PNG image with transparency in the middle and shadows around the edge - it needs to have 9 distinct areas: 4 for each corner, 4 for each edge, and a completely transparent 1x1 pixel area in the middle. For example if your shadow extends 6 pixels into your image, your image would be 13x13 with the 6 pixel wide/high borders and the 1x1 area in the middle. Then you set it as a scalable image using:
newImage = [image stretchableImageWithLeftCapWidth:6 topCapHeight:6];
UPDATE: Since iOS 5.0 stretchableImageWithLeftCapWidth:topCapHeight: is deprecated so only use this if you still want to support iOS 4.x devices. If you want to support only iOS 5.0+ devices use this instead:
newImage = [image resizableImageWithCapInsets:UIEdgeInsetsMake(6, 6, 6, 6)];
Then you put the image on the parent view so it takes up the entire area of the scroll view. If you want the shadows to go OVER your scrollable elements, (so your scroll view looks inset/behind the rest of the page) then place a transparent UIView over the top with the shadow image on it so that it shows through to your scroll view behind it.
Dont forget to:
#import <QuartzCore/QuartzCore.h>
If you want to use
myView.layer.borderWidth = 2;
myView.layer.borderColor = [UIColor blackColor].CGColor;
To get the CGColorRef from an UIColor you can also use this example:
myView.layer.borderWidth = 2;
myView.layer.borderColor = [UIColor blackColor].CGColor;
myView.layout.borderColor generates an incompatible pointer warning when using UIColor, and did not change the border for me.
Using CGColorRef worked for me instead:
CGFloat lComponents[4] = {0,0,0,1};
CGColorSpaceRef lColorSpace = CGColorSpaceCreateDeviceRGB();
myView.layer.borderColor = CGColorCreate(lColorSpace, lComponents);
CGColorSpaceRelease(lColorSpace);
Related
I'm looking for a way to add a solid color border to an existent image with Core Image. I've found the filter list reference but there is no one to make it.
Help !!
We need to have the CIImage extent or the CGRect in which we want to create the solid border. Than, We can draw a CIImage forming a solid line in the specified area, and repeat the steps for 3 more times for different positions to draw a complete solid rectangle. Following is the piece of code which will draw a straight solid line above the specified area.
CIImage *overlay1 = [CIImage imageWithColor:[CIColor colorWithRed:255/255.f green:0/255.f blue:0/255.f alpha:1.00f]];
overlay1 = [overlay1 imageByCroppingToRect:image.extent];
overlay1 = [overlay1 imageByApplyingFilter:#"CIPerspectiveTransformWithExtent" withInputParameters:#{#"inputExtent":[CIVector vectorWithCGRect:image.extent],#"inputTopLeft":[CIVector vectorWithCGPoint:CGPointMake(topLeft.x - 5, topLeft.y + 5)],#"inputTopRight":[CIVector vectorWithCGPoint:CGPointMake(topRight.x + 5, topRight.y + 5)],#"inputBottomLeft":[CIVector vectorWithCGPoint:CGPointMake(topLeft.x - 5, topLeft.y )],#"inputBottomRight":[CIVector vectorWithCGPoint:CGPointMake(topRight.x + 5, topRight.y ) ]}];
overlay = [ overlay1 imageByCompositingOverImage:overlay];
I have kept the width for 5 pixels. topLeft , topRight.... are the respective CGPoint for the position. For a complete rectangle you will also need bottomLeft and bottomRight.
Overlay is the original CIImage .
This isn't exactly what you asked about, but it might be better if you just want to display the image with a border (rather than actually drawing a border onto it)...
You can use CALayer to add borders (and rounded corners, shadows, etc.) to any UIView...
// imgView is an instance of UIImageView, but this works with any UIView
imgView.layer.borderWidth = 2.0f;
imgView.layer.borderColor = [[UIColor blackColor] CGColor];
You also need to #import <QuartzCore/QuartzCore.h> and link to the QuartzCore framework for this to work.
i have a scroll view loaded with 3 view controllers. each view controller is drawing its layers with that code -
(there us more then that but I pulled it out to check if it will help). still i have very crappy sliding.
any help ?
shani
CALayer *sublayer = [CALayer layer];
sublayer.backgroundColor = [Helper cardBackGroundColor:card].CGColor;
sublayer.shadowOffset = CGSizeMake(0, 3);
sublayer.shadowRadius = 5.0;
sublayer.shadowColor = [UIColor blackColor].CGColor;
sublayer.shadowOpacity = 0.8;
sublayer.frame = CGRectInset(self.view.layer.frame, 20, 20);
sublayer.borderColor = [UIColor blackColor].CGColor;
sublayer.borderWidth = 2.0;
sublayer.cornerRadius = 10.0;
[self.view.layer addSublayer:sublayer];
Drawing things with CALayer often yields poor performance. We usually use a stretchable image to get adequate performance. When you think of it, it does make sense to render it before hand rather than using the iPhone's limited processing power to render it in real time.
It's possible that you can get adequate performance from CALayer, but drawing a png will probably still be faster, thus saving battery life time.
EDIT: So here's an example to explain the concept.
This code actually replaced a CALayer drawing that was too slow.
UIImageView *shadow = [[UIImageView alloc] initWithFrame:frame];
shadow.image = [[UIImage imageNamed:#"shadow.png"] stretchableImageWithLeftCapWidth:16.0 topCapHeight:16.0];
[contentView addSubview:shadow];
[shadow release];
shadow.png is 34 by 34 pixels and contains a shadowed square. Thanks to the stretchable image it's possible to resize the square without stretching the shadow. For more information about this I would suggest reading the documentation for stretchableImageWithLeftCapWidth:topCapHeight:. Also Google will help you find guides on how to work with stretchable images. If you have more questions I'll be happy to answer them.
You have a mask (assuming you somewhere say masksToBounds=YES) and a shadow on this layer. Both cause an off screen rendering pass.
Please watch the WWDC 2010 Session 425 - Core Animation in Practice Part 2
Which you can find here;
http://developer.apple.com/videos/wwdc/2010/
Our main UIView is a UIScrollView with a fixed background image (very common, obviously). In that scrollView, we have several UIViews that hold content and scroll up and down as the user scrolls (also common). Those UIViews each have their own background, a simple gradient from white to black.
The goal is to have the background gradient of those (inner) UIViews be partially opaque AND use a CGBlendMode other than "kCGBlendModeNormal" (specifically, "kCGBlendModeOverlay"). You should be able to see through to the "parent" scrollView’s fixed background image as the UIViews scroll up and down above it.
- (void)drawRect:(CGRect)rect {
gradientStart = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
gradientEnd = [UIColor colorWithRed:0 green:0 blue:0 alpha:1.0];
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[2] = { 0.0f, 1.0f };
NSArray *colors = [NSArray arrayWithObjects:(id)gradientStart.CGColor, (id)gradientEnd.CGColor, nil];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)colors, locations);
CGColorSpaceRelease(colorSpace);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetAlpha(context, 0.50); //this works!
CGContextSetBlendMode(context, kCGBlendModeOverlay); //doesn’t seem to do anything!
CGContextClearRect(context, rect);
CGPoint startPoint, endPoint;
startPoint.x = 0.0;
startPoint.y = 0.0;
endPoint.x = 0.0;
endPoint.y = rect.size.height;
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGGradientRelease(gradient);
[super drawRect:rect];
}
Everything works as expected except the CGContextSetBlendMode, which is ignored. We can't seem to find a way to change the blendMode of a UIView relative to what is behind it, the same way you can with alpha. Please note that this is different than building up multiple layers in a SINGLE UIView; in that case, this technique does change the blendMode of the layers "on top". We want to see through to the parent scrollView's fixed background image (as we scroll the child view up and down above it), with both an alpha and an overlay blend applied.
Here's an image showing the issue: http://img2.sbck.us/blendmode.png
Thanks in advance for your help!
I believe what you want is not possible with your current setup. On iOS, it is simply not possible for the blend mode of a view to have an effect on the stuff that is drawn under the view. You would have to draw the scroll view's background and the gradients in the same view.
This is possible, at least with two image views. It might even be possible with more general views. The approach is to implement drawRect in the parent view, and do as follows:
Determine the rect for the foreground view.
Convert the rect in the foreground view to a rect in the background view.
Begin a new graphics context.
Draw the background with the proper blend mode.
Draw the foreground with the proper blend mode.
Extract the image from the graphics context.
End the graphics context.
Use the extracted image accordingly.
This allows a foreground image to blend with a background image.
Seems like you could do this by setting the 'compositingFilter' property of your view's CALayer. The comment in CALayer.h says "A filter object used to composite the layer with its (possibly filtered) background. Default value is nil, which implies source-over compositing."
Alas, CoreImage which provides the filters is not (officially) available on iOS.
I guess your other alternative would be to use OpenGL. You could still use UIView with OpenGL after a fashion by rendering your UIView's into images which could then be used a textures.
I like the way this (http://shakeitphoto.com/) application puts a border around the image.. i would like to do something similar in my application but not sure how should I go about doing it.
Any ideas on how given a UIImage can I wrap a frame around it?
From that website, it appears you want a border with a shadow. There's 2 reasonable options, 3 if you don't care about the shadow.
If you don't care about the shadow, you can just do something like
#import <QuartzCore/QuartzCore.h> // this should be at the top
// inside your view layout code
myImageView.layer.borderColor = [UIColor whiteColor].CGColor
myImageView.layer.borderWidth = 5;
This will give you a 5-pixel white border inset into the view, layered on top of the view's contents (e.g. the image). What it won't give you is a shadow. If you want the shadow, there's 2 other options.
You could just create an image that includes the border and the shadow, and nothing else. Just make everything else alpha-transparent. Then you can simply layer this image on top of the one you want to display (either with 2 imageviews, or by creating a third image out of the 2). This should work fine, but it won't scale to different image sizes. In the case of the linked app, the image size is always the same so they could be using this.
The other option is to simply draw the border and shadow on top of your image in a new image. Here's a bit of sample code that will do this - it creates a new image the same size as your original, but with a white, shadowed border:
- (UIImage *)borderedImage:(UIImage *)image {
// the following NO means the new image has an alpha channel
// If you know the source image is fully-opaque, you may want to set that to YES
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
[image drawAtPoint:CGPointZero];
CGContextRef ctx = UIGraphicsGetCurrentContext();
const CGFloat shadowRadius = 5;
CGContextSetShadowWithColor(ctx, 0, shadowRadius, [UIColor blackColor].CGColor);
[[UIColor whiteColor] set];
CGRect rect = (CGRect){CGPointZero, image.size};
const CGFloat frameWidth = 5;
rect = CGRectInset(rect, frameWidth / 2.0f, frameWidth / 2.0f);
UIBezierPath *path = [UIBezierPath bezierPathWithRect:rect];
path.lineWidth = frameWidth;
[path stroke];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
// note: getting the new image this way throws away the orientation data from the original
// You could create a third image by doing something like
// newImage = [UIImage imageWithCGImage:newImage.CGImage scale:newImage.scale orientation:image.orientation]
// but I am unsure as to how orientation actually affects rendering (if at all)
UIGraphicsEndImageContext();
return newImage;
}
(note: this code has not been compiled and could contain bugs)
I have a UIImageView that displays a bigger image. It appears to be centered, but I would like to move that image inside that UIImageView. I looked at the MoveMe sample from Apple, but I couldn't figure out how they do it. It seems that they don't even have an UIImageView for that. Any ideas?
What you need is something like (e.g. showing the 30% by 30% of the top left corner of the original image):
imageView.layer.contentsRect = CGRectMake(0.0, 0.0, 0.3, 0.3);
Description of "contentsRect":
The rectangle, in the unit coordinate space, that defines the portion of the layer’s contents that should be used.
Original Answer has been superseded by CoreAnimation in iOS4.
So as Gold Thumb says: you can do this by accessing the UIView's CALayer. Specifically its contentRect:
From the Apple Docs: The rectangle, in the unit coordinate space, that defines the portion of the layer’s contents that should be used. Animatable.
Do you want to display the image so that it is contained within the UIImageView? In that case just change the contectMode of UIImageView to UIViewContentModeScaleToFill (if aspect ratio is inconsequential) or UIViewContentModeScaleAspectFit (if you want to maintain the aspect ratio)
In IB, this can be done by setting the Mode in Inspector.
In code, it can be done as
yourImageView.contentMode = UIViewContentModeScaleToFill;
In case you want to display the large image as is inside a UIImageView, the best and easiest way to do this would be to have the image view inside a UIScrollView. That ways you will be able to zoom in and out in the image and also move it around.
Hope that helps.
It doesn't sound like the MoveMe sample does anything like what you want. The PlacardView in it is the same size as the image used. The only size change done to it is a view transform, which doesn't effect the viewport of the image. As I understand it, you have a large picture, and want to show a small viewport into it. There isn't a simple class method to do this, but there is a function that you can use to get the desired results: CGImageCreateWithImageInRect(CGImageRef, CGRect) will help you out.
Here's a short example using it:
CGImageRef imageRef = CGImageCreateWithImageInRect([largeImage CGImage], cropRect);
[UIImageView setImage:[UIImage imageWithCGImage:imageRef]];
CGImageRelease(imageRef);
Thanks a lot. I have found a pretty simple solution that looks like this:
CGRect frameRect = myImage.frame;
CGPoint rectPoint = frameRect.origin;
CGFloat newXPos = rectPoint.x - 0.5f;
myImage.frame = CGRectMake(newXPos, 0.0f, myImage.frame.size.width, myImage.frame.size.height);
I just move the frame around. It happens that portions of that frame go out of the iPhone's view port, but I hope that this won't matter much. There is a mask over it, so it doesn't look weird. The user doesn't totice how it's done.
You can accomplish the same by:
UIImageView *imgVw=[[UIImageView alloc]initwithFrame:CGRectMake(x,y,height,width)];
imgVw.image=[UIImage imageNamed:#""];
[self.view addSubView imgVw];
imgVw.contentMode = UIViewContentModeScaleToFill;
You can use NSLayoutConstraint to set the position of UIImageView , it can be relative to other elements or with respect to the frame.
Here's an example snippet:
let logo = UIImage(imageLiteralResourceName: "img")
let logoImage = UIImageView(image: logo)
logoImage.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(logoImage)
NSLayoutConstraint.activate([logoImage.topAnchor.constraint(equalTo: view.topAnchor,constant: 30),
logoImage.centerXAnchor.constraint(equalTo: view.centerXAnchor),logoImage.widthAnchor.constraint(equalToConstant: 100),logoImage.heightAnchor.constraint(equalToConstant: 100)
])
This way you can also resize the image easily. The constant parameter represents, how far should a certain anchor be positioned relative to the specified anchor.
Consider this,
logoImage.topAnchor.constraint(equalTo: view.topAnchor,constant: 30)
The above line is setting the top anchor of the instance logoImage to be 30 (constant) below the parent view. A negative value would mean opposite direction.