macOS comes with an exceptionally amazing photo management app, and a basic image viewing app that can open most image formats including RAW images. If you need to stitch photos on macOS though, you’re going to have to buy an app to do the trick. There is one clumsy, time consuming alternative which is to tinker with the Preview app but this is something that ought to be easy and it is if you can find the right app, which we did. Tunacan is a free app that can stitch photos on macOS. It has in-app purchases but those allow you to unlock other file formats. It supports PNG and JPG with the free version and that should cover most needs.
Stitch photos on macOS
Download Tunacan and drag & drop the photos you want to stitch together on to the app.
When you add the photo(s), Tunacan automatically stitches them together. It chooses the order itself however, you can change it and doing so is easy. Click the close button next to the image you want to remove. Then, click the plus button on the side of the remaining image(s) that you want to add the second image to.
When you’ve arranged the images the way you want to stitch together, click the Export button at the top and save them wherever you want. The final image will not have any watermark whatsoever. The app will line the images up correctly and make sure no part of any image is being cut out.
If you want, you can add a space between the two images that you’re stitching. There’s a Spacing tool in the column on the right. You can use the slider or enter a precise numerical value in pixels and add space between the images that you’re stitching together. As you add space, the preview pane will show you what it looks like.
It goes without saying that the space will only be transparent for PNG images. For JPEG/JPG images, which do not support transparency, the space will be filled in with white.
Tunacan isn’t the only app that can stitch photos on macOS. There are other apps but they’re not free and most of them are geared towards creating panoramas. If you need something that gives you a simple canvas that can be resized, and that you can paste and reposition images on, you’re going to be advised to buy expensive apps like Adobe’s Photoshop which, for a basic thing like this, is overkill.