Three longer answers about joining pictures
A step panel can hold one clause of explanation before it stops being a control and starts being an essay. These three pages are where the rest of the explanation went.
They exist because putting pictures edge to edge is easy right up until it isn’t, and it stops being easy in three predictable places: the pictures are different sizes, the join shows, or the thing you get back is too tall to be any use. Each page takes one of those, works through what the tool is actually doing to your pixels, and tells you which setting to reach for — including the times when the honest answer is to change nothing at all and accept a band of colour beside the shorter picture.
Nothing here is a tutorial you are meant to read before starting. Open the joiner, get as far as the thing that bothers you, then come back to whichever of these is about that thing.
What to read, and when
- Joining pictures that aren’t the same sizeStart here if one picture is taller than the other. It walks each of the four sizing policies through the same awkward pair and shows what each one throws away.
- Seams, gutters and the colour behind themFor when the join itself is visible: whether to close the gap or open it deliberately, how to pick a ground colour nobody notices, and why a see-through background disappears in a JPEG.
- Joined, and now it’s enormousSix screenshots stacked can make a picture fifteen thousand pixels tall. This one does the arithmetic, finds the ceiling your browser draws at, and suggests what to do once you have hit it.
What you won’t find written up here
There is no page about blending two frames into one another, none about floating a badge over a photograph, and none about hitting a target in kilobytes. Those are genuinely different jobs with genuinely different answers, and a guide here pretending to cover them would be three paragraphs of hedging. The writing on this site stays inside one question: two or more pictures, touching along a straight edge, and what happens at that edge.