Resize with fit, cover, and crop position

A resize starts by choosing the canvas, then the crop policy. fit inside places the whole frame inside 400 × 400 without enlargement. cover fills 600 × 300, so this landscape frame loses a strip from the top or bottom. The kept region can be the centre, the top edge, or a high-entropy area. A square cover on a landscape image would only crop the left and right sides, so north would not move the frame; the wider target makes the vertical crop visible.

Fixed-coordinate crops, arbitrary-angle rotation, and flips are covered in Basic geometry transforms: resize, crop, rotate, and flip.

Input

Night photograph used for fit and cover — **Input: JPEG**1938 × 1292

Four canvases

The reference images come from govips v2.19.0 thumbnail loading on libvips 8.17.3, WebP quality 82, with enlargement disabled. north maps to libvips crop=low: on this wider target the crop is vertical, so the low coordinate keeps the top edge. sharp expresses the same product intent with position: "north".

Night scene scaled inside a 400-pixel box — **fit inside**400 × 267, 14,990 bytes

Night scene covered to 600 by 300 from the centre — **cover centre**600 × 300, 30,842 bytes

Night scene covered to 600 by 300 from the top — **cover north**600 × 300, 26,506 bytes

Night scene covered to 600 by 300 by entropy — **cover entropy**600 × 300, 30,600 bytes

if err := vips.Startup(nil); err != nil { return err }
defer vips.Shutdown()

write := func(name string, width, height int, crop vips.Interesting) error {
    image, err := vips.NewThumbnailWithSizeFromFile("input.jpg", width, height, crop, vips.SizeDown)
    if err != nil { return err }
    defer image.Close()
    params := vips.NewWebpExportParams()
    params.Quality = 82
    data, _, err := image.ExportWebp(params)
    if err != nil { return err }
    return os.WriteFile(name, data, 0o644)
}
if err := write("fit-inside.webp", 400, 400, vips.InterestingNone); err != nil { return err }
if err := write("cover-centre.webp", 600, 300, vips.InterestingCentre); err != nil { return err }
if err := write("cover-north.webp", 600, 300, vips.InterestingLow); err != nil { return err }
return write("cover-entropy.webp", 600, 300, vips.InterestingEntropy)

const jobs = [
  ['fit-inside.webp', { width: 400, height: 400, fit: 'inside', withoutEnlargement: true }],
  ['cover-centre.webp', { width: 600, height: 300, fit: 'cover', position: 'centre', withoutEnlargement: true }],
  ['cover-north.webp', { width: 600, height: 300, fit: 'cover', position: 'north', withoutEnlargement: true }],
  ['cover-entropy.webp', { width: 600, height: 300, fit: 'cover', position: 'entropy', withoutEnlargement: true }],
];
for (const [name, resize] of jobs) {
  await sharp('input.jpg').resize(resize).webp({ quality: 82 }).toFile(name);
}

jobs = [
    ("fit-inside.webp", "none", 400, 400),
    ("cover-centre.webp", "centre", 600, 300),
    ("cover-north.webp", "low", 600, 300),
    ("cover-entropy.webp", "entropy", 600, 300),
]
for name, crop, width, height in jobs:
    image = pyvips.Image.thumbnail("input.jpg", width, height=height, size="down", crop=crop)
    image.write_to_file(name, Q=82)

vips thumbnail input.jpg 'fit-inside.webp[Q=82]' 400 --height 400 --size down --crop none
vips thumbnail input.jpg 'cover-centre.webp[Q=82]' 600 --height 300 --size down --crop centre
vips thumbnail input.jpg 'cover-north.webp[Q=82]' 600 --height 300 --size down --crop low
vips thumbnail input.jpg 'cover-entropy.webp[Q=82]' 600 --height 300 --size down --crop entropy

Where the interfaces diverge

fit-inside is 400 × 267 and each cover variant is 600 × 300; all four are 3-band images without alpha. sharp uses its bundled libvips 8.18.7, while the other three use system libvips 8.17.3. An entropy crop depends on image content distribution, so do not assume it maps to fixed coordinates.

Whether a large thumbnail can stay on a sequential path depends on the access mode. See sequential access, random access, and materialisation.

Resize with fit, cover, and crop position

Input

Four canvases

Where the interfaces diverge

Next

Sources