I know similar questions have been asked before, so don't get snarky and link to previous answers. The reason I am repeating this is that none of the answers have worked.
I have a UIWebView, and I want to draw a pretty drop-shadow behind it. I have tried subclassing and using some CoreGraphics goodness in drawRect:, but to no avail. Can anyone point me in the right direction? Thanks.
You could place a UIImageView under the UIScrollView with a slight offset, and give the image view a shadowy-looking image.
In this case, it would be convenient to use the stretchableImageWithLeftCapWidth:topCapHeight: method of UIImage to get a shadow image that can have nicely blurred edges and corners without distorting if you alter its size.
I think the usual quartz shadows are hard to apply to a UIWebView since you don't really have access to the raw drawing code, which would be the best place to plug that in.
Addendum Here's a sample drop shadow image:
. It has 4 pixel cap size all around, for use with the above stretchableImage method, and an alpha of 80% (so it's 20% transparent in the middle, tapering out at the edges). Feel free to use it. They're easy to make with a selection + feathering in your favorite graphics app.
Related
I am using CIContext method - (void)drawImage:(CIImage *)im inRect:(CGRect)dest fromRect:(CGRect)src to draw my image to screen. But I need to implement zoom-in/zoom-out method. How could I achieve it? I think zoom-in could be achieved increasing dest rect, because apple docs says:
The image is scaled to fill the destination rectangle.
But what about zoom-out? Because if dest rectangle is scaled down, then image is drawn in it's actual size, but only part of image is visible then (part that fits in dest rectangle).
What could you suggest?
You may try using this for image resizing (zooming). Hope this helps you.
Take a look at this little toy app I made
It's to demonstrate the NSImage version of your CIContext method:
- (void)drawInRect:(NSRect)dstRect
fromRect:(NSRect)srcRect
operation:(NSCompositingOperation)op
fraction:(CGFloat)delta
I did this to find out exactly how the rects relate to each other. It's interactive, you can play with the sliders and move/zoom the images. Not a solution, but it might help you work things out.
You can use CIFilter to resize your CIImage before drawing. Quartz Composer comes with a good example of using this filter. Just look up the description of the Image Resize filter in QC.
EDIT:
Another good filter for scaling is CILanczosScaleTransform. There is a snippet demonstrating basic usage.
I have been looking for the solution on the web for a long time. Most tutorials are fairly simple about adding shadow to a UIView. I also noticed that if we add a shadow to an UIImageView. The shadow shape could perfectly fit the shape of the content image if the image itself has alpha channel in it. Say for example, if the image is an animal with transparent background, the shadow shape is also the same as that animal (not a rectangle shadow as same as UIImageView frame).
But these are not enough. What I need to do is to add some changes to the shadow so it may have some rotation angle and compressed (squeezed or shift) effect so that looks like the sunlight comes from a certain spot.
To demonstrate what I need, I upload 2 images below, which I captured from the Google Map App created by Apple. You can imagine the Annotation Pin is an image which has the Pin shape, so the shadow is also "pin shaped", but it is not simply "offset" with a CGSize, you can see the top of the shadow is shifted right about 35 degrees and slightly squeezed the height.
When we tap and hold and pin, the shadow is also animated away from the pin, so I believe that such shadow can be made programmably.
The best shadow tutorial I can found so far is http://nachbaur.com/blog/fun-shadow-effects-using-custom-calayer-shadowpaths But unfortunately, that cannot make this effect.
If anyone know the answer or know any better words to search for, please let me know. Thank you.
(Please note that the shape of the image is dynamic in the App, so using any tool like Photoshop to pre-render the shadow is not an option.)
In order to create dynamic effects like this, you have to use Core Graphics. It's incredibly powerful once you know how to use it. Basically you need to set a skew transform on the context, set up a shadow and draw the image. You will probably have to use transparency layers as well.
It doesn't sound like you can use CALayer shadows, since that is meant to solve a specific use-case. The approach Apple takes with the pin marks on the map is to have two separate images that are created ahead of time (e.g. in Photoshop) and they position them within the map relative to a reference point.
If you really do need to do this at run-time, it should still be possible by using either Core Graphics or ImageKit. To get a blurred shadow appearance, you can use the kCICategoryBlur CIFilter. You can then convert the image to grayscale. And to get that compressed look you just need to resize and skew the image.
Once you have two separate images, you can either take the CGImageRef for the shadow image and can set that as the content of another sublayer, or you can add it as a separate view.
If you know what all the shapes are, you could just render a shadow image in Photoshop or something.
So I want to have a view (NSView, NSOpenGLView, something CG related?) which basically displays a map. Such as:
http://dump.tanaris4.com/map.png
Obviously that looks horrible, but I did it using an NSView, and it draws SO slow. Clearly not designed for this.
I just need to allow users to click on the individual (x,y) coordinates to make changes, and zoom into a certain area (to see it better).
Should I go the OpenGL route? And if so - any suggestions as to how to get started? (I was able to follow the guide to draw a triangle, so that's good).
I did find this post on zooming in an NSView: How to implement zoom/scale in a Cocoa AppKit-application
My concern is if I'm drawing over 6000 coordinates and the lines connecting them, this isn't efficient at all.
I don't think using OpenGL would be of any good here. The problem does not seem to be the actual painting, but rather the rendering strategy. You would need a scene graph of some kind to dynamically handle level of detail and culling.
Qt has all this packaged in a nice class class QGraphicsScene (see http://doc.qt.nokia.com/latest/qgraphicsscene.html for reference, and http://doc.qt.nokia.com/main-snapshot/demos-chip.html for an example).
Some basic concepts you should consider using:
http://en.wikipedia.org/wiki/Scene_graph
http://en.wikipedia.org/wiki/Quadtree
http://en.wikipedia.org/wiki/Level_of_detail
Try using core graphics for this, really there is so much that could be done. Watch the video Practical Drawing for iOS Developers from WWDC 2011 and it should give an over view of what can be done with CG.
I believe even CoreGraphics will suffice for what you want to achieve, and that should work under a UIView if you draw the rectangle of your view completely under the DrawRect method of your UIView (you must overload this method). Please see the UIView Class Reference. I have a mobile application that logs points on the UIMapKit, kind of like Nike+, and it certainly works well for massive amounts of points/line segments. There is no reason why this simple approach cannot work for you as well.
I'm trying to use a CAGradientLayer as a background for a UITableView. Everything works well until the overlaying view is scrolled, at which point then the pre-rendered background scrolls up and out of the way along with the original screen of data.
This is code that is being migrated from an iOS 3.1.3 app using a UIImage as a background to something device/resolution independent-looks great, works well, but sniffing the device type and using an alternate png isn't the sort of code that I want to ship, much less maintain.
Any suggestions as to how to do this?
Found the solution to what I was trying to solve, courtesy of Matt Gallagher:
http://cocoawithlove.com/2009/08/adding-shadow-effects-to-uitableview.html
His blog post has quite a few nice touches, including shadowing relevant cells instead of the whole table (mentioned as a performance issue in Noah's response).
You may have to make the table view transparent, and add the gradient layer to the table's superview. Keep in mind that your scrolling performance is probably going to be hideous—Core Animation will have to composite every subview of the table for every frame it displays. You may be able to slightly mitigate this by setting the cells' layers to rasterize themselves, as described here, but expect things to be pretty choppy regardless.
I'm working on an iPhone app that has some non-rectangular UI elements. Currently, I'm subclassing UIView, and in drawRect I'm using a CGPathRef to draw black border and a color-filled interior.
I'd like to make these items look more like "buttons", though, so I'd like to have some of the same sort of "glass effects" that are used on e.g. the icons for an iPhone app (when you don't set UIPrerenderedIcon to true), or in other buttons.
I hunted around, and found this, which seems to be close to what I need:
Gradients on UIView and UILabels On iPhone
But I'm having difficulty figuring out how to clip the gradient to my shape.
It seems like the mask property on the view would be the right place to go, which seems like it would call for me to create a new CALayer object, with the clipping somehow applied to it.
I'm hoping there's some nice convenience function for doing this, though if I need to write something more complicated, that's OK, too. I'm just having difficulty figuring out how to apply the path as a mask. I'm unsure if I need to create a new drawing context and draw the path into it? And then use CGContextClip?
I think I've got a lot of the right pieces figured out, I'm just having difficulty understanding how to assemble them.
Could someone please point me in the right direction? (I'm happy to read more in the docs, just point me in the right direction, please.)
You can create a CAShapeLayer and set its path to your CGPathRef. Then set the mask property of a CAGradientLayer to your shapeLayer.