Note: By default you are working on the non-retina version. You can download the trial app, or you can get the full app on the Mac App Store. To follow along with this set of PaintCode tutorials, you’re going to need PaintCode. Without further ado, it’s time to get started! Getting Started If you are new to Core Graphics, check out our Core Graphics tutorial series. Also, it is helpful (but not 100% necessary) if you have some basic knowledge of Core Graphics. To get the most of this tutorial, you need some basic knowledge of iOS development. However, any opinions in this article are honest and my own. And finally, since you’re creating your view in code you can do some cool things you couldn’t do if you were pre-generating the graphics – like easily changing the color of various aspects of the control at runtime.įull disclosure: We received some review copies of PaintCode to generate this tutorial. By drawing a view in code, you no longer have to include the images in your binary, reducing your binary size. If you were writing the Core Graphics code manually, it would take you much longer than using PaintCode. After all the pixels have been iterated through, we draw a new UIImage and return it.PaintCode is a neat app where you can draw user interfaces like in Photoshop – but instead of generating an image, it generates Core Graphics code! From there we are iterating through every pixel of the image, checking if the color matches the color to be replaced (or is close enough given the tolerance we defined), and replaces that color with the new one if it does. The actual color changing happens from line 66 onward. That’s the most important rule of unsafe Swift. If you are manually allocating memory, you need to deallocate it too. I like to have the defer block with the deallocate method right after the allocate method, that way it is easy to see that the memory allocated is also being deallocated. The defer statement is automatically executed when the program exits the scope where the defer statement is defined. With the defer statement, you don’t have to think about any of that. If you are writing complex functions, this might be hard to do. We could manually deallocate the memory used in every place we can escape the scope. I find the best way to do this is to use a defer statement. The byte count is something we need when we are allocating the correct amount memory to be used with this method.īecause we are allocating memory, that means we need to deallocate the memory to avoid memory leaks. Then we calculate how many bytes are in our bitmap. ![]() We break the color into red, green, blue, and alpha values. Through lines 26–39 we are creating variables that we will use later in the function. My first priority is always easily readable code. ![]() Converting SwiftUI Image to UIImage and then CGImage makes for clearer code. We could go straight from SwiftUI Image to CGImage, but that requires a lot more parameters to initialize. When we are setting our Image() we need to dip down on UIKit a bit to use UIImage. This article at has some great basic info on unsafe Swift, including this handy table on the different kinds of pointers. We will use unsafe mutable pointers to access specific pixels of an image in memory and change some of those pixels (that’s why it’s called mutable). These kind of errors can be hard to debug. If you don’t deallocate your memory, you will have memory leaks and at some point your app will crash or freeze because the device runs out of memory. The compiler doesn’t protect you or warn you when you are doing something wrong. It requires you to do things by hand that normal safe Swift would do automatically, like allocating and deallocating memory. Unsafe Swift is not automatically a bad thing. You can still access these things if you want to, this way of working is called unsafe Swift. Everything needs to be initialized before we use them and memory is allocated and deallocated automatically. That means Swift prevents us having direct access to memory. Unsafe Swiftīy default Swift is a memory safe language. That will require you to go through every pixel in that given image, get the color of that pixel, check if it matches the color you want to replace, and then rewrite the color information for that pixel. ![]() So you have an image (like the rainbow we are using here) and for some reason you need to replace one of the colors with another. ![]() You should use them whenever they are enough to get the job done, since they make the code easy to understand. In most cases SF Symbols and view modifiers are enough to get the desired results.
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