#Xcode ios memory monitor how to#
#Xcode ios memory monitor simulator#

We can use the ImageIO framework to resize an image before showing it on screen. In order to effectively test your app across real world scenarios, it is essential to use real mobile devices.

#Xcode ios memory monitor simulator#

While the iOS Simulator can be used to test your app’s basic behaviour, it is severely limited as a testing platform. Luckily for us, the WWDC video does provide a great solution to the problem that we are facing. The Apple iOS Simulator, which ships as part of Xcode, is a tool for developing and prototyping your mobile app. During the resizing process, iOS will still decode and decompress the original image, thus causing an unwanted memory spike. This is because UIImage is expensive for sizing and resizing.

Which does add up to what we saw in the memory report.Ĭool! We have figured out where the memory usage comes from, but how can we reduce the memory footprint to an acceptable level?Īs I mentioned earlier, we try to scale down and redraw the image, but that doesn’t seem to help. Takes our sample image with dimension 3648px × 5472px as an example: (3648 * 5472) * 4 bytes ≈ 80MB It includes tools such as Activity Monitor, Allocations. Typically, 1 pixel of a decoded image will take up 4 bytes of memory - 1 byte for red, 1 byte for green, 1 byte for blue, and 1 byte for the alpha component. We can analyze the usage of memory with the help of Xcode tool instruments. Using Xcodes Memory Graph Debugger Open Xcode Select your device in the Device/Simulator dropdown menu and enable Automatically manage signing Run the code. Yes I know, the video is from 2018, but it’s never too late to learn, right? 😉Īccording to the video, in order to show an image on screen, iOS will first need to decode and decompress the image. Memory use is related to the dimensions of the image, not the file size.

After a few Google searches, I ended up with an amazing WWDC video that introduced a very important concept that we all didn’t know about:

#Xcode ios memory monitor how to#

Without having any clues on how to fix the problem, I head over to the web. One approach we take to tackle this problem is to scale down the image and draw it on screen based on the image view’s frame size, unfortunately, that doesn’t seem to fix our problem. This doesn’t make sense at all! We are loading a 2.4MB image file, how does the memory footprint get so high? Where does all this memory usage come from? 😫 Memory footprint when load HD image on screenĪs you can see, the memory usage spikes up from 8MB to 87MB after the image is loaded.