Pixels that mean millimetres
Most merging works in pixels, and pixels have no size on paper until something decides how many fit in an inch. This page decides first: you choose the paper and the print resolution, and every measurement after that — margins, gaps, the size of a card — is in millimetres that turn into an exact number of pixels. The saved file carries the resolution in its header (the JFIF density in a JPG, the pHYs chunk in a PNG, the page box in a PDF), so a printer set to actual size puts every millimetre where the preview shows it.
What each control does
- Page and resolution. The paper size in millimetres times the DPI gives the pixel size, shown under the controls — A4 at 300 DPI is 2480 × 3508.
- Layout. Two above each other, two side by side, three in a column, or a grid of four, six or eight. The margin and the gap between pictures are in millimetres.
- Fit or fill. Fit keeps each whole picture inside its space on white; fill covers the space and crops the overflow evenly.
- ID card. Front and back at the ISO/IEC 7810 ID-1 size, centred, with a gap you set and cut marks at the corners. The four-corner straightening maps a card photographed at a slant onto a rectangle before it is placed.
A worked example
A card photographed on a desk, front and back, each 4000 × 3000 pixels with the card filling most of the frame at an angle. On A4 at 300 DPI each side becomes exactly 1011 × 638 pixels (85.60 × 53.98 mm). With a 10 mm gap — 118 pixels — the pair is 1394 pixels tall, so it starts 1057 pixels from the top and 735 from the left, centred. The corners you placed decide which part of each photo is straightened into those 1011 × 638 pixels; everything outside them, the desk included, is left out. Saved as PDF the page box is 595.3 × 841.9 points, which is A4.
Privacy, specifically
Identity cards are about the most sensitive pictures anyone puts into a web page, which is the best reason to use one that cannot receive them. Both sides are read, straightened and placed inside this tab; the file is drawn fresh, so camera details and location are not carried into it; nothing is kept when you close the page.
Places pictures at true size on a page and records the print resolution. It does not make a copy official, and it does not check that a card is genuine or readable. Free placement anywhere on the page is not offered here — pictures go into the layout’s spaces.
Snags with pages and cards
How do I put the front and back of my card on one page?
Choose ID card, front + back, add the front and then the back, and drag the four yellow corners on each picture onto the corners of the card. Each side is straightened into a rectangle and placed at 85.60 × 53.98 mm — the ISO/IEC 7810 ID-1 size used by bank cards and most identity cards — one above the other on A4. Print at Actual size and the copy on paper is the size of the card.
The printout came out smaller than the real card. Why?
The printer was set to Fit to page, which shrinks everything to fit its own margins. Choose Actual size (or 100 %) in the print dialog. The saved file carries its print resolution — 300 DPI unless you changed it — so a printer at 100 % reproduces every millimetre the page shows.
What does 300 DPI mean for the file?
Three hundred pixels for every inch of paper. An A4 page at 300 DPI is 2480 × 3508 pixels; at 150 DPI it is half that each way and a quarter of the weight. 300 is the usual choice for photos and documents; 600 suits fine print but makes a much larger file.
Can I add a caption under each picture?
Yes — tick the caption option and a text box appears on each picture's card. Each caption is drawn in a 7 mm band under its picture. Captions are kept only in this tab; they are not saved into an arrangement.
I have more than eight pictures. What now?
One page holds up to eight here, and the page says how many did not fit. For more, merge images to PDF puts them on as many pages as they need, several per page if you like.
Is a copy made this way accepted as an identity document?
That is up to whoever asks for it. This page places both sides at real card size on one page and nothing more; it does not certify anything, and it never says an output is accepted by any authority.
