Once you know the center point, radius and arc rect, you can compute the start and end angles with a bit of trigonometry:. So, to get the angle, you simply take the arc-cosine, which is the inverse of the cosine:.
The first thing you add is a way to convert degrees to radians. In the code above, you define an extension on the Measurement type restricting its usage to angle units. Remaining in Extensions. Before its last curly brace, paste the following code:. After the customary Core Graphics setup, you create a bounding box for the entire footer area and the area where you want the arc to be.
You can then add the path to your context and clip to that path. All further drawing will be restricted to that path. To draw a shadow, you enable shadow drawing, then fill a path. Core Graphics will then fill the path and also draw the appropriate shadow underneath. Well, that sounds like a job for clipping! You can set up clipping so that Core Graphics will only draw in the portion outside the footer area.
Then, you can tell it to fill the footer area and draw the shadow. Since its clipped, the footer area fill will be ignored, but the shadow will show through. You can easily get a path for the outside based on the inside through a neat ability of Core Graphics. You simply add more than one path to the context and then add clipping using a specific rule provided by Core Graphics. For example, you could have a donut shape where the outside is filled but the inside is empty, or a donut-hole shape where the inside is filled but the outside is empty.
You can specify different algorithms to let Core Graphics know how to handle this. In EO, for any given point, Core Graphics will draw a line from that point to the outside of the drawing area.
If that line crosses an odd number of points, it will be filled. If it crosses an even number of points, it will not be filled. So, the outside part, which is the entire footer rect, should be filled, but the inner part, which is the arc path, should not.
You tell Core Graphics to clip to that path and only draw in the outside area. Once you have the clipping area set up, you add the path for the arc, set up the shadow and fill the arc. Build and run the project and, if all goes well, you should now see a shadow underneath the footer:.
You can download the completed version of the project using the Download Materials button at the top or the bottom of this tutorial. The raywenderlich. Get a weekly digest of our tutorials and courses, and receive a free in-depth email course as a bonus!
Learn iOS, Swift, Android, Kotlin, Dart, Flutter and more with the largest and highest-quality catalog of video courses and books on the internet. Lorenzo is a Software Engineer who is passionate about mobile development.
He has been engineering iOS apps since but he Ray is part of a great team - the raywenderlich. Archived Forums. Sign in to vote.
User posted I am trying to draw an arc on a image, as attached. Please suggest the if I am doing something wrong or suggest the best way to do it.
Wednesday, May 18, PM. User posted Before you start drawing the arc CoreGraphics needs a starting point. Thursday, May 19, PM. User posted Thanks Mark for replying. But it doesn't worked. User posted I'm sorry I was mistaken. This is the color of the line over the path you're drawing.
Create an iOS Playground. Paste the above code into the Playground. The bars are drawn using a single path. This path is used to color them in, and then it is stroked to clearly separate the individual bars. Simple shapes can be tedious to make with just the five basic path elements. Core Graphics a. CG provides some convenience functions to add common shapes, such as a rectangle, oval, or a rounded rectangle:.
The calls take a transform object as their last parameter. You will see more about transforms in a future posting, so just pass nil for now. There are also functions that let you make more complex paths in a single call, such as multiple rectangles or ellipses, multiple line segments, or an entire other path. Which one you choose to use depends on what values you have handy. Arc — Give it the center of the circle, its radius, and the starting and ending angles in radians of the arc segment you want.
The section of the circle between the start and ending angles going clockwise or counter-clockwise is what will be drawn. The end of the arc becomes the current point. This code draws the left-hand line, plus the circle:. Relative Arc — This is similar to the regular arc.
Give it the center of the circle, the radius, and the start angle. But rather than giving it an end angle, you tell it how many radians to sweep forward or backward from the start angle:. Under the hood, the current point is connected to the first control point, and then to the second control point forming an angle.
These lines are then used to construct a circle tangent to those lines with the given radius. I was trying to come up with a good use for this function, fellow Nerd Jeremy W. Arc to point could include that initial segment. There are two ways to create a path in your code. The path is consumed when you stroke or fill the path. Each context only has a single path in use. This is an instance you can hang on to and reuse.
For shapes that you use often say the suit symbols in a card game , you would want to make a heart path and club path once and use them to draw over and over. So how do you actually make useful and interesting paths, such as heart-shapes or smiley faces? One approach is to do the math and trial and error and calculate where points, lines, curves, and arcs need to go. Another approach is with software tools. There are applications that let you draw your shapes, and then emit a pile of CG code you can paste into your application.
Core Graphics paths are opaque data structures.
0コメント