Two halves, and where the middle actually is
Cutting a picture in half sounds like the one split that cannot go wrong, and most of the time it does not. The awkward case is an odd width. A 3001-pixel panorama has no middle column of pixels that belongs to both sides, so one half has to be one pixel wider. This board gives the extra pixel to the first half and says so in the inspector: 1501 and 1500, which sum back to 3001. Tools that divide and round down quietly lose that column, and the loss shows the moment the halves are placed together again.
The direction is the other decision. Side by side is the usual answer for a landscape — before and after pairs, a wide shot posted as two pictures, a diptych for a wall. Top and bottom suits a tall screenshot that will not fit one screen, or a portrait split into a head and a body for a two-post story. The board opens side by side and the stacked version is one press away; both are drawn on the picture before anything is written.
A worked example
An odd-width scan cut side by side, run through the exporter’s own planner when this page was built:
3001 × 2000 → 2 files · columns 1501 + 1500 = 3001 px · rows 2000 = 2000 px
| File | Cell | From x, y | Pixels |
|---|---|---|---|
| spread-r1c1.png | row 1 · col 1 | 0, 0 | 1501 × 2000 |
| spread-r1c2.png | row 1 · col 2 | 1501, 0 | 1500 × 2000 |
Book spreads and the centre fold
A scanned open book is two pages with a shadow down the middle. Halving it without thinking gives each page a dark strip along its inner edge. The gutter control removes a band from the centre before the halves are written: set 60 pixels and 30 come off the inner edge of each page. The rest of each page is untouched, and the inspector prints the two page widths so you can see what the gutter cost.
- A flatbed scan at 300 DPI usually needs a gutter of 40 to 120 pixels, depending on how flat the book lay.
- The gutter is thrown away, not hidden: the reassembly check reports it as pixels in no tile.
- If the fold is not in the middle, switch to Guides and drag the cut to where the fold is.
Halving divides; it does not straighten. A spread scanned at an angle comes out as two pages at the same angle, and nothing here rotates or deskews them.
How to do it here
- Open the picture. Drop it on the board, browse, or paste it. It is decoded in this tab.
- Choose the direction. Under Split into equal parts press 2 side by side or 2 stacked.
- Trim the fold if there is one. For a book spread, set a gutter so the centre strip is left out of both halves.
- Cut. Press Cut into 2 files. A ZIP with both halves and an index is written to your downloads.
- Check. Press Check these tiles go back together to rebuild the picture from the two files and compare.
