Three rules for one box
A pixel size handed to you — 1920 × 1080 for a screen, 1200 × 800 for a listing — is a box, and a picture of a different shape cannot fill a box without giving something up. The panel makes you choose what: some of the box (fit inside), some of the picture (fill and crop), or its proportions (stretch). Each choice is printed as the factor it implies, so the arithmetic is never hidden behind the result.
| Rule | Factor | Rendered | File holds | Cut |
|---|---|---|---|---|
| Fit inside | ×0.360 | 1440 × 1080 | 1440 × 1080 | nothing |
| Fill and crop | ×0.480 | 1920 × 1440 | 1920 × 1080 | 360 px |
| Stretch | ×0.480 across, ×0.360 down | 1920 × 1080 | 1920 × 1080 | nothing; distorted |
One edge is often the real requirement. A long edge of 1600 px, or a short edge of 1080 px, keeps the picture’s own shape and lands one side exactly:
| Rule | Factor | File holds |
|---|---|---|
| Long edge 1600 | ×0.400 | 1600 × 1200 |
| Short edge 1080 | ×0.360 | 1440 × 1080 |
What does not change
- Fill and crop never cuts more than the overflow, and never from anywhere but the centre of the longer side. If the subject is off-centre, crop first and size second.
- Above the source size every rule is an enlargement: the kernel interpolates between existing pixels and adds no detail.
- The output is capped at 60 megapixels and 16,384 px on an edge, because a browser canvas past that point fails silently. The panel refuses in figures instead.
Questions about pixel sizes
Which rule gives me exactly the width and height I typed?
Fill and crop and Stretch both do. Fill and crop scales the picture until it covers the box on both sides and cuts the overflow equally from the two ends of the longer side, so nothing is distorted and a strip is lost. Stretch gives each axis its own factor, so nothing is lost and the picture is distorted. Fit inside never cuts and never distorts, which is why one side comes out shorter than the box when the shapes differ.
Why does a 4000 × 3000 photo fitted inside 1920 × 1080 come out 1440 × 1080?
Because the height is the side that binds. 1080 ÷ 3000 is ×0.360, and the same factor on the width gives 1440. The panel prints that factor and both sizes before anything is rendered, so the shortfall is visible rather than discovered after the download.
Where does Fill and crop cut from?
From the centre of the longer side: the overflow is split between the two ends, with any odd pixel going to the far end. The shaded strips on the stage are what will be cut, and the receipt records the kept box and its offset.
Is the long-edge rule the same as fitting inside a square?
Yes. A long edge of 1600 and Fit inside 1600 × 1600 resolve to the same factor. The short-edge rule is the other way round: the shorter side lands on the number and the longer side follows, which is what a thumbnail grid or a minimum-size rule usually wants.
Does typing a pixel size change the DPI?
Not by itself. The resolution tag written into a JPEG or PNG stays at the figure shown under Print; only the pixel count changes. The print size changes with the pixel count, and the panel shows the new size in centimetres or inches next to it.
Neighbouring measurements
Pixels already right and only the print size wrong? Change the DPI and leave the pixels alone.
