I rotate a UIImageView using the following code:
[imageView setTransform:CGAffineTransformMakeRotation(-0.10)];
but it looks blurry after the rotation, like this.
What's the problem?
It could be that the resulting frame isn't aligned on an even integer. When you are drawing on a half-pixel boundary, some of the drawing routines are going to make things look blurry.
If you see any non-integer values, use one of the floor() functions to modify the resulting frame in order to snap it to a boundary.
Related
I am working on a map functionality. The map is built up out of multiple CAShapeLayers with CGPaths from calculated coordinates. I have a clipping problem. Look below on the screenshot where Alaska is badly clipped. The coordinates of the Alaska path extend beyond the bounds of my container layer. In effect, if i make my container layer big enough the clipping effect is gone (of course).
You see a dark line because at the bottom of Alaska is solid from left to right. Also the line is darker than the rest of the map because the map has opacity (it gets darker because it adds up).
I drilled down into the problem and i have narrowed it down to the single big polygon (there are not other polygons responsible for the clipping error).
As a workaround, i make the layer bigger to hide the line, then make the UIView smaller again to hide the line.
I'd like to know what is causing the issue instead of working with workarounds.
After a lot of digging, i managed to find an answer to my own question.
I was rendering the layers to an UIImage for improved performance. The background layer was scaled up by a UIScrollView and then several things went wrong:
Apparently, setting masksToBounds:YES has no effect when using renderInContext, just as it does with the mask property of a CALayer. MasksToBounds (or clipToBounds) only applies to childlayers.
When scaling a bitmap, be sure to include integral values to the scale argument of UIGraphicsBeginImageContextWithOptions. If not, the image will have fractional sizes, e.g. 24.2323 x 34.3290. Btw, that scale argument is used to create amazing detail on Retina screens, but it can be misused to zoom in on CAShapeLayer drawings.
When using fractional size images as a background layer, you get distortion at the edge.
The clipping effect disappeared after i updated my layer to image function. This one did the trick:
- (UIImage *)getImageWithSize:(CGSize)size opaque:(bool)opaque contentScale:(CGFloat)scale
{
CGContextRef context;
size = CGSizeMake(ceilf(size.width), ceilf(size.height));
scale = roundf(scale);
UIGraphicsBeginImageContextWithOptions(size, opaque, scale);
context = UIGraphicsGetCurrentContext();
[self renderInContext:context];
UIImage *outputImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImg;
}
Using ceilf, roundf, or floorf didn't really matter. As long as you lose the fractions.
Sorry if my stupidity wasted any of your time, but perhaps others have the same issue.
I am trying to draw a simple straight line. For this, I am filling an UIImageView with some color with given width as, say 2 pixel and some length. Now user is provided with two UISliders out of which one is used to stretch the line and another slider to rotate. I use myImageView.frame to change the height and CGAffineTransform to rotate. It works fine until I change the rotation angle using slider. But once I rotate the imageview, The slider to stretch doesn't work properly.
I have searched and found that frames won't work after rotating using CGAffineTranfor.
Alternately bounds should work but that didn't work too.
Seeking help. Any brief code will help me.
Thanks in advance.
Give transformed bounds every time you apply a transform. This should work:
CGRect transformedBounds = CGRectApplyAffineTransform(myView.bounds, myView.transform);
I used CGPath to make a picture with 4 CALayers, how can I zoom in and out?
The picture contained a four different circles, a rectangle, and a more complicated shape.However, I want to make it zoom in and out like UIRefreshControl.
It's unrealistic to control every shape at the same time to make it look like the original.
If you need it:
in your drawInRect: method you can add CGContextScaleCTM (yourContext,scaleX,scaleY); when scaleX and scaleY are CGFloat. Experiment with it. For example you can set scale with a UISlider.
hi all upto now i know making rectangle with the CGrectmake and this rect(frame) i am using as imageview frame like UIImageView *someImage=[[uiimageview alloc]initwithframe:someRect]; now i can add an image with the frame of someRect. my problem here is when the coordinates like
(rectangleFirstx-coordinate,tectangleFirstY-cordinate)=(10,10)
(rectangleLastx-cordinate,rectangleLasty-cordinate)=(17,7) this, how can i give frame to the uiimageview....This is like a inclined rectangle..can any one suggest me how to apply frame through the ios library for these type of coordinates..Thanks in advance..
Your example isn't very clear because a rectangle with opposite corners at (10,10) and (10,7) can be in any one of a myriad of different orientations, including one perfectly aligned along the x and y axis.
What you can certainly do is create a UIImageView of the desired size and location and then rotate it by using one of many techniques, including animation methods.
[UIImageView animateWithDuration:0.1 animations:^
{
your_UIImageView_here.transform = CGAffineTransformMakeRotation((M_PI/180.0) * degrees);
}];
You can hide the UIImageView until the rotation is done and then show it.
If your question is about how to use the coordinates you provided to arrive at an angle I'd suggest that more data is needed because it is impossible to pick one of the billions of possible rectangles with corners at those two points without more information. Once you have more data then it is pretty basic trigonometry to figure out the angle to feed into the rotation.
I'm having an issue with drawing to areas outside of the MKMapRect passed to drawMapRect:mapRect:zoomScale:inContext in my MKOverlayView derived class. I'm trying to draw a triangle for each coordinate in a collection and the problem occurs when the coordinate is near the edge of the MKMapRect. See the below image for an example of the problem.
In the image, the light red boxes indicate the MKMapRect being rendered in each call to drawMapRect. The problem is illustrated in the red circle where, as you can see, only part of the triangle is being rendered. I'm assuming that its being clipped to the MKMapRect, though the documentation for MKOverlayView:drawMapRect makes me think this shouldn't be happening.
From the documentation:
You should also not make assumptions that the view’s frame matches the bounding rectangle of the overlay. The view’s frame is actually bigger than the bounding rectangle to allow you to draw lines for things like roads that might be located directly on the border of that rectangle.
My current solution is to draw objects more than once if they are in a maprect that is slightly larger than then maprect given to drawMapRect but this causes me to draw some things more than needed.
Does anyone know of a way to increase the size of the clipping area in drawMapRect so this isn't an issue? Any other suggestions are also welcome.
I ended up adding a buffer to the rect passed in to drawMapRect:mapRect:zoomScale:inContext and using that to determine which objects to draw. This results in more objects being drawn than needed, but not by much.