I need to merge two images into one on my Mac. I've read that Preview can do that, but I can't make it work.
Funny that you should mention that, because I had the same problem. I knew how to use Image Magick convert and montage command line tools, but sometimes I'd want to do something more complicated. I searched and found people saying that you could use Preview, but when I tried following their directions, I couldn't make it work.
I'm stubborn and eventually figured it out. Those explanations left out something important. They tell you to paste images into a new or blank image, but they forget to mention that if the images are similar size, it will look like the second image you paste overwrites the first. Total frustration until I realized it was just hiding it and could be moved off easily.
So here's how you do it. Here's a movie that shows the whole process.
I started with a "blank" image. That was just a screenshot I took of a new TextEdit document. I opened two other images that I want to put together. I clicked on one, chose Edit->Select All from the menu, then clicked in the blank image and chose Edit->Paste.
Then I clicked on the other image and again chose Edit->Select All from the menu, then clicked in the blank image and chose Edit->Paste.
That's where I got confused because my first image was now gone. It really wasn't, it was just hidden by the first. If you put your cursor on the image you are seeing, a "hand" icon appears and you can drag it to uncover the other image. Just watch the video if that is confusing.
[This] reminds me of a quotation from somebody that, whenever he tried to explain the logical structure of a programming language to a programmer, it was like a cat trying to explain to a fish what it feels like to be wet. (Saul Gorn)