I'd like to take an image and use it as a mask for a view on which I add numerous image views. I know of the quartz CGContextClipToMask() call but what would be the best way to approach this? Can I override the drawRect method of a container view, call CGContextClipToMask() within it, and then expect its subviews to adhere to that clipping region? It doesn't seem to work.
Do I need to instead add some blocking mask image over top?
Instead of subclassing or overriding drawing functions, I chose to overlay the images with an image that had transparency in the viewable portion. i.e., if my 'surface' was an image of a parchment, and I aimed to draw a bunch of images on it. I would have the parchment image, then a container UIView for any images to be put on that parchment, then a masking image over top of that which was the original parchment image but with the parchment itself converted instead to full transparency, while the surrounding area is left exactly as the background the parchment is on (then all other UI widgets over top of that).
This seems a viable solution in all cases except if one were to need some image to visually animate around and behind the parchment (not my case).
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Xcode 5
I'm trying to learn the auto-layout system. Thought I would start with something simple, but I'm already getting stumped :-)
Scene: Main View -> ImageView -> View
I want to support rotation such that the Image rotates and centers on the screen, using Aspect-Fit content.
I want the smaller view to maintain it's relative position to the top edge of the UIimage view. It does't seem to understand the aspect-fit, and it aligns the sub view along the top of the main view, not the fitted image.
I think it has something to do with the fact that the small view is a sibling of the Image, and not a sub-view. I can only seem to create constraints to the superview.
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You haven't started with something simple!
An aspect fitted image view doesn't actually change its size under auto layout depending on the image, it fits the image into the bounds that the constraints have determined, leaving the rest of its frame blank. If you set a border or background colour on the image view you will see this.
To achieve the effect you're after you would need to do the aspect fitting calculation yourself and modify the sizing constraints on the image view appropriately.
I have one view filling the screen with a background image. Other views (text fields) are in exact positions (the background image includes the text field background images). When I change from 3.5" screen to 4", the text fields don't change in the same way that the background resizes. The bg image simply resizes to fill the screen, but the text fields jump out of alignment.
Is there a way to have two sets of constraints, one for each screen size? or is there a way to have views resize proportionally to another view?
EDIT:
Is there a way to have two sets of constraints, one for each screen
size?
Yes, by adding constraints programatically and checking [[UIScreen mainScreen] bounds] to get the screen size.
or is there a way to have views resize proportionally to another view?
Yes, you could set this up in interface builder. But it will be hard to manage, I would manage the constraints manually in code since you are using a custom background image the textviews need to position exactly
You're going to struggle to get these things to line up properly with the text view backgrounds being part of the background image.
You should amend your image assets and use the background property of UITextField to have an actual background image, and remove the boxes from your main background image. The icons could be separate images as well.
Failing that, it would make more sense to have the image stretch underneath the text boxes rather than on top.
Your layout is doing what it should do based on your description, but the image isn't stretching in the right way. In your screenshots, username is always the same distance from the top, and the others are the same distance from the bottom, but that isn't how image stretching works. I don't know how you've set it up but it would make sense to have a single image the size of the 4 inch screen, which has the bottom cut off for 3.5 inch devices, and constrain everything from the top.
I have an app, its a small game using opengles with GLKit.
No im wondering how it works when i want to draw text on
my screen (if it is possible).
How can i do it?
i draw all of my game objects using images (wrapped in some kind
of sprite). its possible to scale, to move, and to rotate.
everything works fine.
but finding out how it works to print text on that glkview
gets me deep inside of problems ^^
I dont want to use uiimages cause i also dont know how
to present uiimages on a glkview.
There are a number of ways to do what you want:
1) Have an image with all the text glyphs you need in it. For example, if your application is in English, you'd have the 26 uppercase and 26 lowercase letters in the image. Upload that texture to the GPU and use the proper texture coordinates or glSubTexImage2d() to pull out the glyphs you need. (It's not clear to me if this is what you meant by not wanting a UIImage. It doesn't have to be a UIImage, though that's probably easiest.)
2) Every time you need to display text, draw it on the CPU on the fly, and upload the entire word, phrase, or sentence as a texture. You could create a CGBitmapContext and use Core Graphics to draw text to it. Then upload it using glTexImage2D().
3) Get the individual glyphs out of the fonts and draw directly using the bezier curves that make up the glyphs. This allows for 3D extrusion, too. However, this option is the most time consuming to code and probably least performant. It also involves dealing with the many small problems that fonts have (like degenerate segments, and incorrect winding orders). IF you want to go down this path, I think maybe Core Text can help.
There are at least two clean ways to do this, depending on your requirements.
While documentation advises against compositing over a CAEAGLLayer (GLKView), it works quite well, at least in recent iOS versions, when transparent content is layered on top of the CAEAGLLayer. For example, try dropping a UITextView, with opaque set to false and a clear background color, on top of a GLKView in your Storyboard in Interface Builder in the Apple GLKit template or your app. In my test on an iPhone 5, frame rendering time remained around 1ms, even while scrolling in the text view. If your text needs are static, or you don't want the user to interact with the text, use CATextLayer as a child layer of your EAGLLayer instead of a view.
The second approach is to render the text into a texture. You can then composite the text onto your view by disabling the depth buffer and rendering the texture on a full screen rectangle. Look at UIGraphicsBeginImageContextWithOptions to see how to render to an offscreen image with Quartz. UIGraphicsGetImageFromCurrentImageContext allows you to retrieve the UIImage to use as a texture.
I have built so far an application that allows the user to drag and drop images onto a NSImageView. However, I want to be able to move these images by simply clicking on any image and hold down the mouse button to move it's location.
How can I manipulate NSImageView to translate/scale after setting the images down? Is that possible? I've read about the NSAffineTransform, but it seems like that is moving the images before creating the image itself. I already have the images on the canvas, and simply want to click and hold the image and move it with my mouse. Please help anyone!
There are two sides to this.
NSImage is the model object, which you might want to display in different ways, save to disk/archive, etc. If you want to actually change the model (scaling, rotating, etc.), implying a permanent change, then you are going to probably want to look at NSAffineTransform, Quartz drawing, etc.
But you probably didn't mean that. Instead you probably are interested in NSImageView, which is a view object, displaying the contents of the NSImage model object using whatever display attributes are desired. If you only want to change how an image is displayed, not what the actual bytes in the image are, then you are going to manipulate the NSImageView at run-time. You can use NSAffineTransform here as well, but it's somewhat uncommon (and usually unnecessary).
The key thing to note that is the NSImageView inherits from NSView, so you have all its power at your disposal. Take a look at certain methods, such as:
-setFrameSize: - useful for changing the view size, and thus the image display scale
-setFrameOrigin: - useful for changing the view position, and thus the apparent image position
Note again that these have nothing to do with images per se, and apply to all Cocoa views. You may want to take a look at a book like Cocoa Programming for Mac OS X to get you past the basics. (You can then do more interesting things, like rotation, animation, etc.)
i have a scrollview which contains a pdfpage rendered with CATiledLayer, i want to draw stuff onto the pdf page so i created a overlay layer, i need the graphic to look vectorized so i decided to use CATiledlayer for the overlay layer. Only problem is that it is very slow to draw (I'm using beizerpath to draw), then i tried to optimize it by creating the overlay layer with the visible height and width when zooming in and out, so i don't need to create the overlay for the whole content bound. But still no luck , i want to try CALayer but the draw path just becomes blurry and pixelated, so i'm not sure how i can improve on this. I also tried drawinrect but for some reason it doesn't seem to work.
I suggest not using bezierpath to draw annotations since it requires you to redraw the whole path every time the pen moves. It would be better if you draw only the current line segment using CGContextAddQuadCurveToPoint.
At touchMoved, get the current point and 2 prev points
Using those points, get the area where the line should be drawn
draw at that area in drawRect using setNeedsDisplayAtRect
inside drawRect, go to the end of your path and add your new line using CGContextAddQuadCurveToPoint