Six 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 six 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 a handful of predictable places: the pictures are different sizes, the join shows, the thing you get back is too tall to be any use, the captures of one page have to be rebuilt in order, or a portal wants a photograph and a signature in one file. 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 size →Start 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 them →For 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 enormous →Six 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.
• Make one long screenshot from many →Capturing a scrolling page so the pieces overlap cleanly, what the seam detector measures, fixing a seam by hand, covering private details, and what to do when the result is too tall to share.
• Put a photo and signature in one image →For application forms: read the notice first, keep a margin round the signature, resize once, and reach the kilobyte range with quality rather than luck.
• Exam form photo and signature sizes →The pixel and kilobyte limits from published notices in one table, each with its source and the date it was checked — and how kilobytes are counted two ways.

What you won’t find written up here

There is no page yet about blending two frames into one another or floating one photograph over another. Those are real ways of putting pictures together with their own answers, and a guide here pretending to cover them before the tool does would be three paragraphs of hedging. The writing on this site stays with what the tool does today: pictures touching along an edge, what happens at that edge, and the one form job — a photo and signature in a single file — where a kilobyte range is part of the brief.