Did a simple application for line drawing with UIBezierPath, but now need a way to erase the line drawn with UIBezierPath. Is there a way to implement eraser feature for removing the line painting?
If you are using an image as background then you can set the same image as brush pattern to draw the bezierpath it will virtually give you the eraser effect. It works for me. :)
brushPattern=[[UIColor alloc]initWithPatternImage:[UIImage imageNamed:#"image.jpg"]];
// Here image.jpg is you background image
if(erase)
{
[myPath strokeWithBlendMode:kCGBlendModeClear alpha:1.0f];
}
else
{
[myPath strokeWithBlendMode:kCGBlendModeNormal alpha:1.0f];
}
An eraser effectively draws a line that's the same color as the background atop every path that's been drawn thus far. You might need to note that it's an eraser line somewhere so that you can update the eraser line's stroke color if the background color changes, otherwise you lose the illusion of erasure.
Based on your comments on Jeremy's answer, it seems like you're trying to do dashed lines. Have you tried using setLineDash:count:phase:
UIBezierPath *path = [UIBezierPath new];
CGFloat dashArray[3];
dashArray[0] = 8;
dashArray[1] = 3;
dashArray[2] = 8;
[path setLineDash:dashArray count:dashCount phase: 0.0];
Apple has sample code here: http://developer.apple.com/library/mac/#samplecode/BezierPathLab/Introduction/Intro.html
Related
Hi in one of my application i had created a circle using drawrect method on UIView object.Now my concern i want draw a highlight border around the circle for that actually i used
myView.layer.borderWidth =3.0;
myView.layer.borderColor=[UIColor colorWithRed:myView.patternRed green:myView.patternGreen blue:myView.patternBlue alpha:1.0].CGColor;
But due to this code what is happening is a border is creating around the view and it's looks a rectangle, but i want to create a border around the circle itself. So if anyone know how to implement this functionality please let me know. Thanks in advance.
Try this
myView.layer.cornerRadius = 80.0f;
It'll curve your view into a circle.
Thanks.
you have to set some radius for the corners of that view so add this line
myView.layer.cornerRadius=20;
play with the numeric value to match your requirements
I hope it helps
This Works for me:
UIView *myView =[[UIView alloc]initWithFrame:CGRectMake(0,0,100,100)];
[self createRoundUIView:myView:80];
-(void)createRoundUIView:(UIView *)inputView sizeDiameter:(float)diameterSize;
{
CGPoint saveCenter = inputView.center;
CGRect frame = CGRectMake(inputView.frame.origin.x, inputView.frame.origin.y, diameterSize, diameterSize);
roundedView.frame = frame;
roundedView.layer.cornerRadius = diameterSize / 2.0;
roundedView.center = saveCenter;
}
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'm writing some lines of code to get acquainted with the basics of Quartz 2d.
I am trying to draw and image an then clear it through the kCGBlendModeClear blend mode. Here's the code of my UIView subclass code, whose background color is set to orange through IB:
- (void)drawRect:(CGRect)rect {
UIImage *brush = [UIImage imageNamed:#"brush.png"] ;
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetBlendMode(ctx,kCGBlendModeNormal );
CGContextDrawImage(ctx, CGRectMake(100, 100, 26, 25), [brush CGImage]);
CGContextSetBlendMode(ctx, kCGBlendModeClear);
CGContextSetFillColorWithColor(ctx, [UIColor clearColor].CGColor);
CGContextFillEllipseInRect(ctx, CGRectMake(110, 110, 5, 5)); // HERE!
}
Reading the docs and this question I thought that line marked HERE would produce a hole in the image I had previously drawn. Instead it creates a black circle on it (should be orange).
To debug, I tried adding my custom view over an orange uiview. This time my custom view has a black background. The hole of line HERE is correct, but I wonder why the black color of the view. Even more strangely, if I do myView.backgroundColor I can set a background color (shouldn't this be overridden by my drawRect implementation?).
I am clearly missing some basics of Quartz, can anyone help?
Davide
Couple of things.
First, the Porter-Duff blend modes are only guaranteed to work in bitmap-based contexts. (i.e., contexts created by CGBitmapContextCreate)
Second, kCGBlendModeClear is defined as R = 0 — it doesn't even check src or dst pixels. So even though it's not guaranteed to work here, it appears that it is working correctly.
(see CGContext.h for better explanation than the docs give.)
For kCGBlendModeClear to work the view must not be opaque and must not have a background color set.
In addition, the following line is unnecessary, because kCGBlendModeClear does not care about the fill color:
CGContextSetFillColorWithColor(ctx, [UIColor clearColor].CGColor);
Is it possible to add a shadow to the text in a UITextField?
As of 3.2, you can use the CALayer shadow properties.
_textField.layer.shadowOpacity = 1.0;
_textField.layer.shadowRadius = 0.0;
_textField.layer.shadowColor = [UIColor blackColor].CGColor;
_textField.layer.shadowOffset = CGSizeMake(0.0, -1.0);
I have a slightly different problem - I want a blurred shadow on a UILabel. Luckily, the solution to this turned out to be number (2) from Tyler
Here's my code :
- (void) drawTextInRect:(CGRect)rect {
CGSize myShadowOffset = CGSizeMake(4, -4);
CGFloat myColorValues[] = {0, 0, 0, .8};
CGContextRef myContext = UIGraphicsGetCurrentContext();
CGContextSaveGState(myContext);
CGColorSpaceRef myColorSpace = CGColorSpaceCreateDeviceRGB();
CGColorRef myColor = CGColorCreate(myColorSpace, myColorValues);
CGContextSetShadowWithColor (myContext, myShadowOffset, 5, myColor);
[super drawTextInRect:rect];
CGColorRelease(myColor);
CGColorSpaceRelease(myColorSpace);
CGContextRestoreGState(myContext);
}
This is in a class that extends from UILabel and draws the text with a shadow down and to the right 4px, the shadow is grey at 80% opacity and is sightly blurred.
I think that Tyler's solution number 2 is a little better for performance than Tyler's number 1 - you're only dealing with one UILabel in the view and, assuming that you're not redrawing every frame, it's not a hit in rendering performance over a normal UILabel.
PS This code borrowed heavily from the Quartz 2D documentation
I don't think you get built-in support for text shadows here, the way you do with UILabel.
Two ideas:
(1) [Moderately tricky to code.] Add a second UITextField behind the original, at a very small offset (maybe by (0.2,0.8)? ). You can listen to every text change key-by-key by implementing the textField:shouldChangeCharactersInRange:replacementString: method in the UITextFieldDelegate protocol. Using that, you can update the lower text simultaneously. You could also make the lower text (the shadow text) gray, and even slightly blurry using the fact that fractionally-offset text rects appear blurry. Added: Oh yea, don't forget to set the top text field's background color to [UIColor clearColor] if you go with this idea.
(2) [Even more fun to code.] Subclass UITextField and override the drawRect: method. I haven't done this before, so I'll mention up front that this depends on this being the designated drawing method, and it may turn out that you have to override another drawing function, such as drawTextInRect:, which is specific to UITextField. Now set up the drawing context to draw shadows via the CGContextSetShadow functions, and call [super drawRect:rect];. Hopefully that works -- in case the original UITextField code clears the drawing context's shadow parameters, that idea is hosed, and you'll have to write the whole drawing code yourself, which I anti-recommend because of all the extras that come with UITextFields like copy-and-paste and kanji input in Japanese.
Although the method of applying the shadow directly to the UITextView will work, it's the wrong way to do this. By adding the shadow directly with a clear background color, all subviews will get the shadow, even the cursor.
The approach that should be used is with NSAttributedString.
NSMutableAttributedString* attString = [[NSMutableAttributedString alloc] initWithString:textView.text];
NSRange range = NSMakeRange(0, [attString length]);
[attString addAttribute:NSFontAttributeName value:textView.font range:range];
[attString addAttribute:NSForegroundColorAttributeName value:textView.textColor range:range];
NSShadow* shadow = [[NSShadow alloc] init];
shadow.shadowColor = [UIColor whiteColor];
shadow.shadowOffset = CGSizeMake(0.0f, 1.0f);
[attString addAttribute:NSShadowAttributeName value:shadow range:range];
textView.attributedText = attString;
However textView.attributedText is for iOS6. If you must support lower versions, you could use the following approach. (Dont forget to add #import <QuartzCore/QuartzCore.h>)
CALayer *textLayer = (CALayer *)[textView.layer.sublayers objectAtIndex:0];
textLayer.shadowColor = [UIColor whiteColor].CGColor;
textLayer.shadowOffset = CGSizeMake(0.0f, 1.0f);
textLayer.shadowOpacity = 1.0f;
textLayer.shadowRadius = 0.0f;
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);