What is the benefit or purpose to change the CALayer position, which is by default in center, don't it suppose to be a center of CALayer? Whats the point changing a center point to bottom right or any other, because bottom right can't be the center of a square.
It's helpful for things like rotation where you may want to rotate around a particular point instead of the center
Related
I have the following problem: I'm scanning a QR Code with AVFoundation. This works quite well and I can also create a border around the code by adding a subview and set the frame attribute by subview.frame = qrCodeObject.bounds. This only has the problem that the border is only a rectangle and dismisses the perspective of the QR code.
I know that the qrCodeObject has a property corners which incorporates the top right, top left, bottom right and bottom left points of the QR code detected.
My question is now: how can I apply those corner points to the "border" view to make this border to have the same perspective as the QR code? Or in other words: how to "transform" the view according to the corner points?
Thanks a lot in advance!
UPDATE:
Here you can see the problem: the red box is a UIView, having it's frame property set to the QR codes bounds property. This misses perspective. I would like to transform the UIView (the red box) to following the corners property of the QR code, which includes the top right, top left, bottom right and bottom left points (CGPoint) of the QR code. It is important to apply this to a UIView, because I later want to apply it to an ImageView. Also a mask is not usable, as it just hides part of the view, but does not stretch or transform the content of the view.
I found a solution: AGGeometryKit did the trick: https://github.com/hfossli/AGGeometryKit/
Thanks everybody for helping!
You can't transform a CGRect that way, as far as I know. (At least I'm unaware of any framework that can do that kind of image processing.)
What you can do is to draw a polygon using the points of the qrCodeObject.
In drawRect of your UIView, change use CGContext and CGPath to draw the path you'd like.
You want your drawing UIView to be the same size as the one showing the QR code so that you don't have to translate the points onto a second coordinate space.
This answer has directions if you need more guidance on how to do that.
Ok, the problem you are facing is that a CGRect can only represent a rectangle that is not tilted or distorted. What you are dealing with is an image that has different kinds of perspective distortion.
I haven't tried to do this, but it sounds like AVFoundation gives you 4 CGPoint objects for a reason. You need to draw those 4 CGPoints using a UIBezierPath rather than trying to draw a CGRect. Simply create a bezier path that moves to the first point, then draws lines to each subsequent point, and finally, back to the first point. That will give you a quadrilateral that takes into account the distortion of your QR code.
CATransform3DRotate could be your friend, here.
https://guides.codepath.com/ios/Using-Perspective-Transforms might be a good starting point.
I'm trying to use paint code to draw a roundrect with different corner radii. I have nearly everything working by drawing two circles and two roundrects. The problem is I can't make one of the roundrects draw at x offset circle radius have width of "frame.width - circle_radius" - the end effect being it keeps aligned to the right hand edge of the frame.
It feels like I should be able to write frame.width - largeCornerRadius in an expression editor but PaintCode objects to the frame reference.
That said, i's beginning to feels like I could write this code quicker by hand :-)
I don't have an answer to my specific stated question but I have discovered a better way to draw my roundrect as four different rects and turning off the roundrects on the "inner corners:
As you'd expect the drawing code is much better and it resizes well with the enclosing frame.
You can also :
use a set of rect, oval or other shapes
select them and "union" to get one bezier curve for the whole shape
selection each point (or a set of points) of the resulting bezier and fix springs on each of them as fixed or fluid from the edge of the surrounding frame.
I see this question is old, but let me show how to achieve this using Springs & Struts.
Let’s use 2 circles and 2 rounded rectangle, each having only one corner rounded, just like you have. Once you draw a Frame around these shapes, their Springs & Struct inspector becomes enabled.
Here you can click each of 6 segments to toggle fixed or flexible dimension for each shape. For Red Circle, make flexible only top and right margin (just like on the image above) and for Blue Circle the opposite margins (bottom and left). Then for both rectangles make flexible size and fixed margins.
For more information, check out our videos, blog, and documentation on this topic.
– PaintCode Support
I'm trying to flip a sprite horizontally i.e.
sprite.scaleX = -1;
What I notice is that the sprite is flipped around its bottom left corner. However since I don't want to mess up my positioning of the sprite (I'd like the sprite to stay in the original place), so I tried to set its anchor point to (1,0)
sprite.anchorPoint = ccp(1,0);
My reasoning is this:
Since the sprite should be flipped around the anchorPoint, if I set the anchorPoint to its bottom right corner then that corner will then become the 'left bottom' corner of the changed sprite; and I should be able to move the sprite using that new anchorPoint just as I do with a normal sprite of anchorPoint (0,0).
However apparently it's not working as I expected. What am I missing?
Edit
What I really want to do is to flip a sprite and then be able to control its position via the left bottom corner - well the left bottom corner of the sprite that I see. I don't think I fully understand how scaleX = -1 is applied relating to the anchorPoint. If somebody can explain to me the concepts behind these parameters then that will greatly help me.
I have to correct myself on making the assertion that setting anchorPoint doesn't help. In fact, setting anchorPoint to (1,0) is exactly the solution to the problem, only that somehow some bug prevented me from recognizing it in my test.
In my app I wanted to position in the center of the screen a UIImage, with the shape of a circle. Then I wanted the user to be able to rotate the image buy touching one specific point on the circumference of the circle, and dragging, just like a wheel, but I have no idea where to start form.
I know I can use the touches began, moved, and ended, but how can I fix a point?
You can adjust the origin property of your UIView. This should force the rotation around that point.
Here is a picture:
Is there a way to expand layer (the area where you draw), to be larger.
At first i thought that (0,0) is the center, but it seems that it is a starting point for layer.
I was planning to draw content at (0,0) then to translate it as necessary.
Or, must i draw whatever i have in center of layer (width/2, height/2) and then translate as necessary?
EDIT_01:
The offset of layer is made by panning gesture recognizer. That is on purpose, since app must have panning of content.
Answers
At first i thought that (0,0) is the center, but it seems that it is a starting point for layer
(0,0) in iOS begins at the top left of the layer, and gets greater going right and down. In OS X, (0,0) begins in the bottom left, and gets greater going right and up.
Is there a way to expand layer (the area where you draw), to be larger
The question I have is, do you need to? This can have performance issues, as you're rendering and storing drawing data when you don't really need to, causing more memory to be used. It looks like your layer is filling the screen correctly, it's just translated incorrectly. If you move it to the correct place, you shouldn't need to expand the layer off screen.
This doesn't mean you can't translate other layers off screen, of course you can. But really you don't want to expand the size of your drawing area to expand off screen.
Must i draw whatever i have in center of layer (width/2, height/2) and then translate as necessary?
If you want them drawn into the center, then yes. You can create your own method to translate your own co-ordinate space into the co-ordinate space of the layer, to make this easier for you.
Documentation
I'd suggest reading this, to get a greater grasp of the geometry workings of CALayer:
https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/CoreAnimation_guide/Articles/Layers.html#//apple_ref/doc/uid/TP40006082-SW1
...and this to get an understanding of drawing techniques:
https://developer.apple.com/library/ios/#documentation/graphicsimaging/conceptual/drawingwithquartz2d/dq_layers/dq_layers.html