I want to implement dialog borders that scale to the size I require the dialog to be. Perhaps there is a better more conventional name for this sort of thing. If there is, if someone would edit the title, that'd be great.
Anyhow, I'd like to do this so I can have dialogs of any size without the visual artifacts that come with scaling border art to small, large, or wacky unproportional dimentions. I have a few ideas on how this is done, but am not sure which is better for iphone. I have a few questions.
1) Should I make a containing view object that basically overloads its drawRect method and draws the images where they should be at their appropriate scale when the method is called, or should I main a containing view object that simply contains 8 UIImageViews? I suspect the latter approach won't work if I need to actively scale the resulting dialog class like in an animation.
1b) If overloading drawRect is the way to go, does someone have some sample code or a link to an example that demonstrates drawing an image directly from drawRect()?
2) Is it generally better to create
a) a 3 x 3 image where the segments are in their appropriate 1x1 grid of the image? If so, is it simple to draw from a portion of this image onto my target view in drawRect (if the former assumption is correct that I should use drawRect)?
b) The pieces separately in 8 different files?
UPDATE:
To clarify, the idea is to take any customized border art and be able to stretch the 2nd, 4th, 6th, and 8th cell (in a 3x3-cell grid) to form a border of any size with just those assets. Stretching just a plain image would result in distortion of the corners, so I'd like to stretch those even numbered cells as needed and tack on the corners so there is no distortion. I'd seen this done before so thought it might be a standard thing and have a standard naming to it other than what I called it.
Anyhow, I was advised that adding 8 UIImageViews to a container would not be as efficient as drawing the UIImages on the fly in drawRect so took that approach using CGContextDrawImage() after applying the necessary transformations to the context to translate and scale the Y. Because this function draws from the bottom left corner of an image but onto a top-left origined UIView, the image is upside down without the Y axis invert. I noticed the suggestion to use UIImage functions like drawAtPoint works as well and similarly but for the invert since UIImage draws in the same orientation as UIViews. I will continue my implementation with the former and see how it goes, but one other question.
Would someone happen to know which of these approaches is more efficeint, faster, etc?
I'm not sure I follow, but here's my best shot at an answer...
Using drawRect: or adding individual UIImageViews to a parent view is entirely up to you. UIImageView gives you a bit of encapsulated functionality for free, but otherwise they are the same as far as appearances go.
If you do want to go the drawRect route, you just need to use UIImage's drawAtPoint: method. Do the math for where you want it to be, and draw it. You can calculate your points based on the parent view's dimensions.
As far as scaling, it's impossible to resize these images without scaling them, so I'd plan ahead and make your originals as large or larger than you ever expect to display them.
Hope that helps a little?
Cheers
If you want a border on a dialog box, assuming the box is a UIView (or subclass), then set the layer's border properties and let the system draw the border for you.
#import <QuartzCore/QuartzCore.h>
// ...
view.layer.borderWidth = 2;
view.layer.borderColor = [UIColor whiteColor].CGColor;
view.layer.cornerRadius = 0; // 0=square corners, >0 for rounded
Related
I have this image:
What I want to do is to add a UITapGestureRecognizer to this image (or I can split the image in the different parts it consists of and add for each part a UITapGestureRecognizer) in order to have different actions according to the leaf tapped. If I split the image in different images each for each leaf the UIImageViews will probably overlap and tapping on one will be recognized as a tap on another one. Having just one image implies knowing the points of the screen that belongs to a leaf rather than to another one.
Any clues on how to do it would be really appreciated.
Thanks
Change your behavior by examining the gesture recognizer's locationInView:.
If you handle the image as one unit, implement this in your gesture recognizer call back to decide which "leaf" (if any) was tapped.
If you handle the image as multiple images, you could also implement it in your callback, or you could also implement in, e.g., your delegate's gestureRecognizerShouldBegin: to suppress events for touches outside the leaf as drawn.
EDIT: I didn't realize that you might also be looking for assistance on figuring out whether a point lies within a leaf. #PhillipMills is correct on this point: we need to know how you are drawing the image.
FOLLOW-UP: This is somewhat outside my area of expertise.
The easiest approach (from a hit-testing standpoint) is to do what #PhillipMills suggested, using Quartz drawing and CGPathContainsPoint(). If you have detailed graphics that you need rendered as a PNG, you could certainly construct a simple path that would be (virtually) overlayed to allow hit testing.
Your other options, AFAIK, are to do hit testing mathematically, but you would basically be reimplementing CGPathContainsPoint() but without a path, or to employ various tricks that look at the color of the pixels at your touch point to do hit testing. Googling will turn up some useful results if you go this route, but honestly for a shape as simple as what you've drawn, just use some UIBezierPath code to recreate in code.
Not sure if this will be helpful but if you get stuck on figuring out which leaf was clicked, you could use an old image map trick we used to use in CD-ROM projects for pixel accurate click tracking on images.
You have your full size image. Make a 25% (or less) scaled version of it. Fill each of the leaf regions you want to track clicks on with a different color; anything you want to ignore make black. When the full size image is clicked, get the x/y coordinates and scale them by the percentage of your scaled image. Then get the pixel color of the scaled image at the scaled x/y coordinate. By determining the pixel color you will know which leaf was clicked.
Sounds clunky but it works really well and is fast.
(all that said, I don't think alpha areas of images trigger the gesture recognizer - so breaking the image up would be less complicated/code intensive.)
If you can break the shape apart into the constituent elements, then you can put each into it's own layer and use the method discussed in this stackoverflow discussion to determine which was touched: Hit Testing with CALayer using the alpha properties of the CALayer contents
I'm basically trying to achieve this effect. It can be done with pretty much a PNG with a transparent hole cut through it, then stacked on top of a photo.jpg UIView. OR, I've also seen a method where you can directly create a mask with CGImageMaskCreate. I don't want to use that feature because I want the user to be able to interact with the photo.jpg layer (by moving it, rotating it, etc.):
Its essentially two UIViews stacked directly on top of each other.
However, what if rather than using blue, I wanted to use another color, or even pattern an image with [UIColor colorPatternWithImage:] for the masking layer? I wouldn't want to make a million different PNGs for each case.
Would I need some way to programmatically recreate my mask? Is there some way to convert my mask shapes into code? Any help is appreciated. Thanks
CALayer has a property called mask, which is another CALayer that defines the mask to use. You could use a CAShapeLayer to define the mask, then set that as the mask of another layer that renders your obscuring image/color/pattern/whatever. You could also use a regular CALayer as the mask with your semi-transparent image as the contents, it depends on whether or not you want the ability to customize the size/shape of the hole.
Caveats: CAShapeLayer is slower than normal layers, and mask is slower than non-masking as well. You may need to make sure performance is acceptable for you. You may also want to try out the shouldRasterize flag, though this will only improve performance (at the cost of memory) as long as the layer is static (i.e. not animating).
So I've been all over the web, trying to figure out a definitive way to do this, and I can't seem to get it. Each of my table view cells has 3 dynamically-loaded images that I need to add rounded corners to. Right now I'm using Quartz and the layer.cornerRadius property of the ImageViews to round the corners, but of course it kills the scrolling performance of the table view.
Browsing online, I can't seem to find an answer to the performance problems. Most threads either end in suggesting the use of pre-rendered static images (not an option for me since the images are loaded dynamically, from the web) or some drawing trick that Loren Brichter came up with for Tweetie- however, the example project he posted on his blog is now a dead link, and I can't find it anywhere.
So basically, my question is how exactly should I go about accomplishing the rounded corners on elements inside a table view cell, without sacrificing performance? Thanks for any help!
Looking at the other answers it looks like you are using a lot of alpha transparency that is going to cost you a lot performance wise. You may consider revisiting that to get additional frames. One idea you may try doing is rendering the rounded image in a graphics context and using that as your cell image instead of the QuartzCore rounding.
Load the image in the imageview
Round the corners
Render the image into a graphics context
Set the imageview with the new image
Turn rounding off
Do all of this in the cellForRowAtIndexPath: method. There may be more efficiencies to be had (like caching the rendered image), but this is a way to at least test out the performance of a pre-rendered rounded image.
What about using a mask concept, and overlaying a mask UIImageView with transparent background over your dynamic images. Havent tried that, my self but it's an option.
I have a png image file that is partly opaque and partly transparent. I display it in a UIImageView as a mask of sorts over another UIImageView layered behind it (as a sibling subview of a common superview). It gives me perfect borders around something painted using a finger on the lower UIImageView in my stack of UIImageViews. Perhaps there are better ways to do this, but I am new-ish, and this is the best way I came up with thus far. None the less, my app is in the App Store and now I want to enhance it to provide more images to use as the mask of sorts over the finger painting. But I don't want to bloat my bundle size by adding more static mask images as I did for the initial implementation. Not to mention I don't want to spend lots of time in photoshop making 100 masks. I'd rather programmatically change the color of the mask, without affecting the clear portion in the middle, which is not a simple regtangle or circle, but rather a complex shape. So my question is this: How can I change the colored portion of my loaded image without affecting the clear color portion in the middle? Is there a reasonably easy way to do this? Essentially I want to do what is described in this post (How would I tint an image programmatically on the iPhone?) without affecting the clear portion of my image. Thanks for any insights.
Have a look at the Tinted Image sample project. Try out the different modes until you get the effect you want.
Currently, I have a UIView subclass that "stamps" a single 2px by 2px CGLayerRef across the screen, up to 160 x 240 times.
I currently animate this by moving the UIView "up" the screen 2 pixels (actually, a UIImageView) and then drawing the next "row".
Would using multiple CALayer layers speed up performance of rendering this animation?
Are there tutorials, sample applications or code snippets for use of CALayer with the iPhone SDK?
The reason I ask is that most of the code snippets I find that demonstrate simple examples of CALayer employ method calls that do not work with the iPhone SDK. I appreciate any advice or pointers.
Okay, well, if you want something that has some good examples of CA good that draws things like that and works on the phone, I recommend the GeekGameBoard code that Jens Aflke published (it is an improved version of some Apple demo code).
Based on what you are describing I think you are doing somthing way more complicated than it needs be. My impression is you want basically a static view that you are animating by shifting its position so that it is partially off screen. If you just need to set some static content in your drawRect going through layers is not going to be faster than just calling CGFillRect() with your color. After that you could just use implicit animations and the animator proxy on UIView to move the view. I suspect you could even get rid of the custom drawRect: implementation with a patterned UIColor, but I honestly have not benchmarked the difference between the two.
What CALayer methods are you seeing that don't work on iPhone? Aside from animation features tied to CoreImage I have not noticed much that is missing. The big thing you are likely to notice is that all views are layer backed (so you do not need to do anything special to use layers, you can just grab a UIView's layer through the layer accessors methos), and the coordinate system has a top left origin.
In any event, generally having more things is slower than having fewer things. If you are just repeating the same pattern over and over again you are likely to find the best performance is implementing a custom UIView/CALayer/UIColor that knows how to draw what you want, rather than placing visually identical layers or views next to each other.
Having said that, generally layers are lighter weight than views, so if you have a lot of separate elements that you need to keep logically separated you will find that moving to layers can be a win over using views.
You might want to look at -[UIColor initWithPatternImage:] depending on exactly what you are trying to do. If you are using this two pixel pattern as a background color you could just make a UIColor that draws it and set the background.
What CALayer methods are you seeing that don't work on iPhone?
As one example, I tried implementing the grid demo here, without much luck. It looks like CAConstraintLayoutManager and CAConstraint are not available in QuartzCore.h.
In another attempt, I tried a very simple, small 20x20 CALayer object as a sublayer of my UIView's layer property, but that didn't show up.
Right now, I have a custom UIView of which I override the drawRect method. In drawRect I grab a context and render two types of CGLayerRefs:
At "off" cells I draw the background color across the entire 320x480 canvas.
At "on" cells, I either draw a single CGLayerRef across a grid of 320x480 pixels (initialization) or across a 320x2 row (animation).
During animation, I make a UIImageView clip view from 320x478 pixels, and draw a single row. This "pushes" my bitmap up the screen two pixels at a time.
Basically, I'd like to test whether or not using CALayer will accomplish two things:
Make my rendering faster, if CALayer has less overhead than what I'm doing now
Make my animation smoother, by letting me transition a layer up the screen smoothly
Unfortunately, I can't seem to get a basic CALayer working at the moment, and haven't found a good chunk of sample code to look at and play with.