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• Removing the image from an IKImageView

  - by Brian Postow

  I have an IKImageView that is coming up effectively un-initialized. This is happening effectively in an error-state (The user is unregistered) so I haven't had a chance to put an image in it yet. In 10.6, this comes up fine, with a black rectangle. In 10.5, however, it comes up with garbage. some rectangles of noise, some rectangles of copies of the desktop, etc. I've tried setting the ZoomFactor to 0.0, I've tried setting the image to nil, but it appears that the problem is beyond that. any ideas? (My next kludge is going to be to ship tiny blank image with the app, and try to get it to load that... but that's kind of silly)

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• CGContext rotation

  - by kasperjj

  I have a 100x100 pixel image that I want to draw at various angles rotated around the center of the image. The following code works, but rotates around the original origo of the coordinate system (upper left hand corner) and not the translated location. Thus the image is not rotated around itself but around the upper left corner of the screen. CGContextRef context = UIGraphicsGetCurrentContext(); CGContextTranslateCTM(context, -50, -50); CGContextRotateCTM (context, 0.3); CGContextTranslateCTM(context,768/2,1024/2); [image drawAtPoint:CGPointMake(0,0)]; I tried doing the same using CGAffineTransform, but got the same results.

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• Using CATransition in a viewController

  - by eco_bach

  Hi I'm trying to implement the ViewTransitions code sample from Apple, but putting all the logic in my viewController instead of my applicationDelegate class. I'm getting a bizarre error when I try to compile. I'm importing QuartzCore in my viewcontroller implementation as #import _kCATransitionFade", referenced from: _kCATransitionFade$non_lazy_ptr in ViewTransitionsAsViewControllerViewController.o (maybe you meant: _kCATransitionFade$non_lazy_ptr) Anyone have any ideas?

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• Quartz2D and gradient line

  - by Fry Constantine

  how can i draw gradient line with quartz2d?

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• Building a clip area in a UIView from path objects in its subviews

  - by hkatz

  I'm trying to produce a clipping area in a UIView that's generated from path objects in its subviews. For example, I might have one subview containing a square and another containing a circle. I want to be able to produce a clip in the parent superview that's the union of both these shapes. Can someone explain how to do this? About all I've been able to figure out so far is that: 1 - the superview's drawRect: method is called before its subviews' drawRects are, and 2 - the ContextRef that's accessible in all three instances is the same. Other than that I'm stumped. Thanks, Howard

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• iPhone - Is it ok to override UITableViewCell setSelected:animated

  - by Brian

  I am drawing custom UITableViewCells. My cells are opaque and are completely drawn in the drawRect of the cell to help with performance. I want to handle the look of a selected cell myself. If I don't, then the contents of my cell is covered up by the selectedBackgroundView that is added. Is it common or acceptable to override the setSelected:animated method of my cell so this is done properly. I guess if I did that, then I would not call the super's setSelected method since I would be handling how the cell will show that its selected. I would also have to set the selected property of the cell. Any help would be great. Thanks.

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• How to fill a path with gradient in drawRect:?

  - by Derrick

  filling a path with a solid color is easy enough: CGPoint aPoint; for (id pointValue in points) { aPoint = [pointValue CGPointValue]; CGContextAddLineToPoint(context, aPoint.x, aPoint.y); } [[UIColor redColor] setFill]; [[UIColor blackColor] setStroke]; CGContextDrawPath(context, kCGPathFillStroke); I'd like to draw a gradient instead of solid red, but I am having trouble. I've tried the code listed in the Question/Answer: http://stackoverflow.com/questions/422066/gradients-on-uiview-and-uilabels-on-iphone which is: CAGradientLayer *gradient = [CAGradientLayer layer]; [gradient setFrame:rect]; [gradient setColors:[NSArray arrayWithObjects:(id)[[UIColor blueColor] CGColor], (id)[[UIColor whiteColor] CGColor], nil]]; [[self layer] setMasksToBounds:YES]; [[self layer] insertSublayer:gradient atIndex:0]; However, this paints the entire view that this is in with the gradient, covering up my original path.

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• iPhone image distortion

  - by Corey Floyd

  Are there any reasons why the simulator will display UIImageViews properly, but incorrectly on the iPhone? My Process: An image in a PNG file Start a UIGraphicsBeginImageContext() Draw the PNG in a CGrect Draw text in the CGRect Create an UIImage from the context Set the image of a UIImaveView to the UIImage Set the frame of the UIImageView to the size of the PNG Add as a subview Outcome: The image does not display correctly. The rightmost 1-3 pixels of the image is just a vertical white line. This occurs only on the device and not on the simulator. I can fix the problem, but only by increasing the size of the UIImageView. If I increase the size.height of the UIImageView by 1 pixel, it displays the UIImage correctly. Of course, these leaves the iPhone to scale my image before drawing it on screen which is not desirable. Any ideas why this occurs or any fixes for it? (I will post my code if needed)

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• Drawing triangle/arrow on a line with CGContext

  - by Pete

  Hi, I am using the framework of route-me for working with locations. In this code the path between two markers(points) will be drawn as a line. My Question: "What code should I add if I want to add an arrow in the middle(or top) of the line, so that it points the direction" Thanks - (void)drawInContext:(CGContextRef)theContext { renderedScale = [contents metersPerPixel]; float scale = 1.0f / [contents metersPerPixel]; float scaledLineWidth = lineWidth; if(!scaleLineWidth) { scaledLineWidth *= renderedScale; } //NSLog(@"line width = %f, content scale = %f", scaledLineWidth, renderedScale); CGContextScaleCTM(theContext, scale, scale); CGContextBeginPath(theContext); CGContextAddPath(theContext, path); CGContextSetLineWidth(theContext, scaledLineWidth); CGContextSetStrokeColorWithColor(theContext, [lineColor CGColor]); CGContextSetFillColorWithColor(theContext, [fillColor CGColor]); // according to Apple's documentation, DrawPath closes the path if it's a filled style, so a call to ClosePath isn't necessary CGContextDrawPath(theContext, drawingMode); }

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• Image animation over CGContextDrawPDFPage

  - by BittenApple

  I'm modifying the QuartzDemo sample app from Apple. In QuartzViewController.m I have modifications (by DyingCactus) which replac the back button and add a method to handle the back button press as follows: -(void)viewDidLoad { // Add the QuartzView [scrollView addSubview:self.quartzView]; //add custom back button if this is the PDF view... if ([self.quartzView isKindOfClass:[QuartzPDFView class]]) { self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"QuartzDemo" style:UIBarButtonItemStyleBordered target:self action:@selector(myBackButtonHandler:)]; } } - (void)myBackButtonHandler:(id)sender { [self.quartzView setFrame:CGRectMake(150, -200, 100, 200)]; [UIView beginAnimations:nil context:nil]; [UIView setAnimationDelegate:self]; [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)]; [UIView setAnimationDuration:1.0]; [self.quartzView setFrame:CGRectMake(150, 0, 100, 200)]; [UIView commitAnimations]; } - (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context { [self.navigationController popViewControllerAnimated:YES]; } I have a PNG image in resources folder called "bookmark.png" and would like to have that image animate as in animation in the example above. The image can be loaded in an UImageview or something and lets say that I have one called bookmark. How do I call that instead of self.quartzview in this part of code: [self.quartzView setFrame:CGRectMake(150, -200, 100, 200)]; [UIView beginAnimations:nil context:nil]; [UIView setAnimationDelegate:self]; [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)]; [UIView setAnimationDuration:1.0]; [self.quartzView setFrame:CGRectMake(150, 0, 100, 200)]; [UIView commitAnimations];

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• Image animation over CGContextDrawPDFPage

  - by BittenApple

  I have a pdf page displayed with CGContextDrawPDFPage in QuartzDemo sample application. I want to keep this page shown and have an image slide in from top over this page, just as it can be seen in the iBooks application. It's a book, the sliding image is a bookmark that slides in when you are about to close the book. I added this code by DyingCactus (hint: im a newbie to obj c and iphone dev) as follows: In QuartzViewController.m, the animation starts to show but the view slides away before the animation is finished, in fact I think the animation goes on while the view is sliding away. -(void)viewWillDisappear:(BOOL)animated { [self.quartzView setFrame:CGRectMake(150, -200, 100, 200)]; [UIView beginAnimations:nil context:nil]; [UIView setAnimationDuration:1.0]; [self.quartzView setFrame:CGRectMake(150, 0, 100, 200)]; [UIView commitAnimations]; } How can I keep the view visible and finish the animation before view disappears?

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• iphone: how to do Page turning

  - by srnm12

  hi frnds, I am facing the problem from a month and didn't find anything from google.. I am using UIView for pdf display. there is no problem with pdf but problem is with transition. I have to turn each page of pdf with realistic page turn exp. I search, dig a lot about that but i didn't get anything that how to do that. I don't want to use any API'S like codeflake or any other. all i want to do this by my own programming. First i read that this can be done using cocos2d or CAAnimation but i want to know how? b'coz realistic page i think so is completely 3d concept. Let me know guys how to do thay?? here's the example video: http://www.youtube.com/watch?v=oknMWvRO2XE I want animation just like in video....

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• trying to draw scaled UIImage in custom view, but nothing's rendering

  - by Ben Collins

  I've created a custom view class and right now just want to draw an image scaled to fit the view, given a UIImage. I tried just drawing the UIImage.CGImage, but as others have attested to on this site (and in the docs), that renders the image upside down. So, at the suggestion of an answer I found to another question, I'm trying to draw it directly, but nothing is rendering in the view and I'm not sure why. Here's my drawing code: - (void)drawRect:(CGRect)rect { // Drawing code [super drawRect:rect]; if (self.originalImage) { [self drawImage]; } } - (void) drawImage { if (CGSizeEqualToSize(originalImage.size, self.frame.size) == NO) { CGFloat scaleFactor = 1.0; CGFloat scaledWidth = 0.0; CGFloat scaledHeight = 0.0; CGPoint thumbPoint = CGPointMake(0.0, 0.0); CGFloat widthFactor = self.frame.size.width / originalImage.size.width; CGFloat heightFactor = self.frame.size.height / originalImage.size.height; if (widthFactor < heightFactor) { scaleFactor = widthFactor; } else { scaleFactor = heightFactor; } scaledWidth = originalImage.size.width * scaleFactor; scaledHeight = originalImage.size.height * scaleFactor; if (widthFactor < heightFactor) { thumbPoint.y = (self.frame.size.height - scaledHeight) * 0.5; } else if (widthFactor > heightFactor) { thumbPoint.x = (self.frame.size.width - scaledWidth) * 0.5; } UIGraphicsBeginImageContext(self.frame.size); CGRect thumbRect = CGRectZero; thumbRect.origin = thumbPoint; thumbRect.size.width = scaledWidth; thumbRect.size.height = scaledHeight; [originalImage drawInRect:thumbRect]; self.scaledImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); } else { self.scaledImage = originalImage; } } My understanding (after studying this a bit) is that the UIGraphicsBeginImageContext function creates an offscreen for me to draw into, so now how do I render that context on top of the original one?

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• Is there a way to initialize ImageKit's IKSaveOptions to default to TIFF with LZW compression?

  - by Rei

  I'm using Mac OS X 10.6 SDK ImageKit's IKSaveOptions to add the file format accessory to an NSSavePanel using: - (id)initWithImageProperties:(NSDictionary *)imageProperties imageUTType:(NSString *)imageUTType; and - (void)addSaveOptionsAccessoryViewToSavePanel:(NSSavePanel *)savePanel; I have tried creating an NSDictionary to specify Compression = 5, but I cannot seem to get the IKSaveOptions to show Format:TIFF, Compression:LZW when the NSSavePanel first appears. I've also tried saving the returned imageProperties dictionary and the userSelection dictionary, and then tried feeding that back in for the next time, but the NSSavePanel always defaults to Format:TIFF with Compression:None. Does anyone know how to customize the default format/compression that shows up in the accessory view? I would like to default the save options to TIFF/LZW and furthermore would like to restore the user's last file format choice for next time. I am able to control the file format using the imageUTType (e.g. kUTTypeJPEG, kUTTypePNG, kUTTypeTIFF, etc) but I am still unable to set the initial compression option for TIFF or JPEG formats. Thanks, -Rei

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• Blending Three Images into Graphics Context Using Alpha Blend Mode kBlendModeOverlay

  - by steganous

  Does kCGBlendModeOverlay not work exactly like Photoshop's Overlay blending mode? I'm trying to overlay three images into a graphic context via: [uiimageGreen drawAtPoint:CGPointMake(x, y) blendMode:kCGBlendModeOverlay alpha:1.0]; [uiimageRed drawAtPoint:CGPointMake(x, y) blendMode:kCGBlendModeOverlay alpha:1.0]; [uiimageBlue drawAtPoint:CGPointMake(x, y) blendMode:kCGBlendModeOverlay alpha:1.0]; In the end, if I overlay just two of the three, the result is much closer to my desired output color in places where both images intersect. Adding the third image, however, causes the first-drawn image's color to be dominant in the resulting mix of colors. (e.g. in the above code, green comes out dominant, when the result should actually be white) Do you get the same result if you try?

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• CGContextSetRBStrokeColor to replace, not add, for alpha?

  - by Peter Hajas

  I use CGContexts to allow the user to draw in my application, here's an example: CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); CGContextSetLineWidth(UIGraphicsGetCurrentContext(), size); CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(),r,g,b,a); I want the user to have an "eraser" tool that actually erases - it can't draw white (that would add white to the image, which may not have a white background) or alpha (or else the stroke won't do anything). Is there a way to do this? Perhaps replacing contents of a CGContext or UIImage?

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• How do I remove those rotation artefacts from my CATiledLayer?

  - by Felix

  Hello all, I have a CATiledLayer into which I render content in the following method - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx I used the QuartzDemo code to draw a pattern. This works very well until I apply a rotation transform to the layer's parentLayer (a UIView): rotated: These zigzag artefacts become worse when I start drawing lines and texts into the CATiledLayer. I applied the transform as follows (I also tried using an affine transform on the view itself): self.containerView.layer.transform = CATransform3DMakeRotation(angleRadians, 0.0f, 0.0f, 1.0f); I transform the containerView rather than the layer itself, as I have several layers in that view that I would like to rotate at the same time without changing the relative positions. I did not have problems when rotating UIImageViews in the past. Is there a way that I can rotate the CATiledLayer without these problems? Any help would be greatly appreciated. Yours, Felix

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• How do I set the current point in a CG graphics context?

  - by Joe

  When running the code below in the iphone simulator I get the error : CGContextClosePath: no current point. Why is the current point not being set? Or is the context not set to the correct state? CGContextBeginPath(ctx); CGMutablePathRef pathHolder; pathHolder = CGPathCreateMutable(); //move to point for the initial point NSLog(@"Drawing a state point %f, %f", [[holder.points objectAtIndex:0] floatValue], [[holder.points objectAtIndex:1] floatValue]); CGPathMoveToPoint(pathHolder, NULL, [[holder.points objectAtIndex:0] floatValue], [[holder.points objectAtIndex:1] floatValue]); for(int x = 2; x < [holder.points count] - 1; x += 2) { NSLog(@"Drawing a state point %f, %f", [[holder.points objectAtIndex:x] floatValue], [[holder.points objectAtIndex:(x+1)] floatValue]); CGPathAddLineToPoint(pathHolder, NULL, [[holder.points objectAtIndex:x] floatValue], [[holder.points objectAtIndex:(x+1)] floatValue]); } CGContextClosePath(ctx); CGContextFillPath(ctx);

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• Add shading to clipped UIView

  - by huggie

  I'm creating an iphone application. I have this UIView whose content is clipped with a path. I want to add shading and/or shadow to it. What's the best way to do this? For shadow, I tried CGContextSetShadow() but it doesn't seem to have an effect (perhaps it's drawing outside the shown region?) . How about shading? I want it to appear along the path. What's the best way to go about it? Is it to create another narrow clip strip along the original clipping path (if it's possible to have two clip path... ) Or does this need to be done in another CALayer? I am not even sure what that is yet.

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• Can't compile code when working with CALayer

  - by Sheehan Alam

  For some reason I get linker errors when I try and use CALayer: "_OBJC_CLASS_$_CALayer", referenced from: I have imported the following headers: #import <Foundation/Foundation.h> #import <UIKit/UIKit.h> #import <QuartzCore/QuartzCore.h> Code: arrowImage = [[CALayer alloc] init];

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• How can I call the iPhone to draw using other method?

  - by Tattat

  I have a view with a class called "drawingViewController", and I have the drawRect method: - (void)drawRect:(CGRect)rect { CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(context, 2.0); CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor); CGContextMoveToPoint(context, 0.0f, 0.0f); CGContextAddLineToPoint(context, 100.0f, 100.0f); CGContextStrokePath(context); } But I wanna to define some other drawing method, but it did't work, how can I do so apart from calling drawRect method? thz in advance.

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• Creating a mask from a graphics context

  - by Magic Bullet Dave

  I want to be able to create a greyscale image with no alpha from a png in the app bundle. This works, and I get an image created: // Create graphics context the size of the overlapping rectangle UIGraphicsBeginImageContext(rectangleOfOverlap.size); CGContextRef ctx = UIGraphicsGetCurrentContext(); // More stuff CGContextDrawImage(ctx, drawRect2, [UIImage imageNamed:@"Image 01.png"].CGImage); // Create the new UIImage from the context UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); However the resulting image is 32 bits per pixel and has an alpha channel, so when I use CGCreateImageWithMask it doesn't work. I've tried creating a bitmap context thus: CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); CGContextRef ctx =CGBitmapContextCreate(nil, rectangleOfOverlap.size.width, rectangleOfOverlap.size.height, 8, rectangleOfOverlap.size.width , colorSpace, kCGImageAlphaNone); UIGraphicsGetImageFromCurrentImageContext returns zero and the resulting image is not created. Am I doing something dumb here? Any help would be greatly appreciated. Regards Dave

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• Custom UILabel does not show text.

  - by Oscar

  Hi! I've made an custom UILabel class in which i draw a red line at the bottom of the frame. The red line is showing but i cant get the text to show. #import <UIKit/UIKit.h> @interface LetterLabel : UILabel { } @end #import "LetterLabel.h" @implementation LetterLabel - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // Initialization code } return self; } - (void)drawRect:(CGRect)rect { CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0); CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0); CGContextBeginPath(UIGraphicsGetCurrentContext()); CGContextMoveToPoint(UIGraphicsGetCurrentContext(), 0.0, self.frame.size.height); CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), self.frame.size.width, self.frame.size.height); CGContextStrokePath(UIGraphicsGetCurrentContext()); } - (void)dealloc { [super dealloc]; } @end #import <UIKit/UIKit.h> #import "Word.h" @interface WordView : UIView { Word *gameWord; } @property (nonatomic, retain) Word *gameWord; @end @implementation WordView @synthesize gameWord; - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { self.backgroundColor = [UIColor whiteColor]; LetterLabel *label = [[LetterLabel alloc] initWithFrame:CGRectMake(0, 0, 20, 30)]; label.backgroundColor = [UIColor cyanColor]; label.textAlignment = UITextAlignmentCenter; label.textColor = [UIColor blackColor]; [label setText:@"t"]; [self addSubview:label]; } return self; } - (void)drawRect:(CGRect)rect { // Drawing code } - (void)dealloc { [gameWord release]; [super dealloc]; } @end

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• iPhone Dev:Blurring of CALayers when rotated

  - by user153231

  Hello All, I have a CALayer with a png image as its content.When rotation is applied the layer looks blurry. I've searched for a cause for this problem and found out that the problem might be the half pixel problem, which makes the layer blurry if its frame.origin lays on fractions like 96.5, and they suggest to make the origin a whole number. Now, my layer's origin contains fractions because of the rotation i make as in: tempLayer.anchorPoint = CGPointMake(0.5,0.5); tempLayer.position = CGPointMake(200,100); tempLayer.bounds = CGRectMake(0,0,70,88); tempLayer.transform = CATransform3DMakeRotation(10.f*M_PI/180.f, 0.f, 0.f, 1.f); tempLayer.contents = (id)myImage; Basically i have three questions: 1) Is there a better way to rotate the layer? 2) The frame values are derived from the anchorPoint, position, bounds and transform values, how can i round my frame values to integer values and keep my rotation intact? 3) Can the CGRectIntegral function help me? If yes how? Thank you all in advance.

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• How to draw a drop shadow AND gradient with quartz2d?

  - by Luke

  Hello! I've a custom shape drawing using coregraphics and i want to add a drop shadow and a gradient to it also. I've been trying and searching a lot of informations on how to combine and do this, but i can't get it to work. I'm able to draw only one either. Anyone doing this already or know how to do this? Thank you.

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