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Inner shadow effect on UIView layer?
(17 answers)
Closed 9 years ago.
I want to apply inner-shadow to a UILabel. I have a solution, but it's not good enough. Anyone with a better solution?
// UILabel subclass
- (void) drawTextInRect:(CGRect)rect {
CGSize myShadowOffset = CGSizeMake(0, 2);
float myColorValues[] = {255, 0, 0, 1};
CGContextRef myContext = UIGraphicsGetCurrentContext();
CGContextSaveGState(myContext);
CGColorSpaceRef myColorSpace = CGColorSpaceCreateDeviceRGB();
CGColorRef myColor = CGColorCreate(myColorSpace, myColorValues);
CGContextSetShadowWithColor (myContext, myShadowOffset, 5, myColor);
CGContextSetBlendMode(myContext, kCGBlendModeLighten);
[super drawTextInRect:rect];
CGColorRelease(myColor);
CGColorSpaceRelease(myColorSpace);
CGContextRestoreGState(myContext);
}
I'm familiar with the layer property of UILabel, but shadow offset gives us a outer-shadow, NOT inner-shadow (unless i'm missing something).
Borrowing on Ruben's answer above, if you do the reverse ie. set your text color equal to your background color (with low alpha) and then set the shadow to be a stronger color, it creates a decent inset effect. Here's what I mean (Note: My view background is white):
cell.textLabel.textColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.5];
cell.textLabel.shadowColor = [UIColor darkGrayColor];
cell.textLabel.shadowOffset = CGSizeMake(-1.0,-1.0);
[cell.textLabel setText:#"Welcome to MyApp!"];
and this is the output
This would probably only work on very light backgrounds as I suspect it will create unwanted overlay on darker backgrounds.
You can ofcourse vary the shadowOffset to change the direction of light.
I tried to do this but finally opted to use the default shadowOffset and play with the shadowColor to give the inner drop shadow effect to the text. In small texts it gives you a good inner shadow effect. For example, if you have a grayColor background and apply a whiteColor to the shadow, then you have an acceptable inner shadow effect.
Sometimes, it's better to design those texts with graphic tools and make localized copies if needed.
Answer here : Inner Shadow in UILabel Long code but it seems to work
Related
I'm drawing a full circle using arcs in Core Graphics. Each arc of the circle is a different colour. If I use standard colours (e.g. [UIColor redColor] ) it draws fine. But if I specify a custom colour (e.g. a custom red colour [UIColor colorWithRed:193 green:69 blue:57 alpha:1] ) the colour is lost and it comes out white?!
Screen shot below, I've also code there for a slight shadow and semi-transparent circle.
My code is below, its contained within the DrawRect method of my custom view. Any ideas on how I can use custom colours for the stroke of each arc?
for (DoughnutChartSliceObject *slice in _slices) {
CGContextAddArc(ctx, self.frame.size.width/2, self.frame.size.height/2, _radius, slice.startAngleInRadians, slice.endAngleInRadians, 0);
[slice.colour setStroke];
//Define line width and cap
CGContextSetLineWidth(ctx, _stroke);
CGContextSetLineCap(ctx, kCGLineCapButt);
//draw it!
CGContextDrawPath(ctx, kCGPathStroke);
}
The components of the UIColor are from 0.0 to 1.0. Thus, I think you want:
[UIColor colorWithRed:193.0/255.0 green:69.0/255.0 blue:57.0/255.0 alpha:1]
I am customizing my UITableView and I figured out how to set the selected color of each cell. In my cellForRowAtIndexPath method, I have the following code:
UIView *bgColorView = [[UIView alloc] init];
[bgColorView setBackgroundColor:[UIColor orangeColor]];
[cell setSelectedBackgroundView:bgColorView];
[bgColorView release];
But it is a solid orange. I want to make it more slick looking, and have it be a slight gradient from light orange to darker orange. How can I do this?
You'd use Core Graphics (a.k.a. Quartz) to draw a gradient in your view's -drawRect: method:
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGFloat colors[8] = {1.0, 0.75, 0.30, 0.5, 0.7, 0.2, 1.0, 0.8};
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient = CGGradientCreateWithColorComponents(space, colors, NULL, 2);
CGContextDrawLinearGradient(ctx, gradient, top, bottom, NULL);
You can limit the area that the gradient fills by creating a path in the current context (ctx) and the clipping to it using CGContextClip(ctx);. top and bottom are CGPoints that define the beginning and end of the gradient.
You will have to override the view's drawRect method to draw the gradient. It can be kind of a PIA, but you can also check out this open source component which may work:
http://cocoacontrols.com/platforms/ios/controls/gradient-view
#Caleb's answer is right on; I do this for a variety of things.
What no one has mentioned is that the view for which you need to implement drawRect: is a custom UITableViewCell.
simple google search will find your answer ....
http://bluesplat-tech.blogspot.com/2009/03/gradient-shading-uiview.html
If you want a complex or subtle gradient, you can set a background image that is partial alpha and set the cell background color to change appearance.
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;