How do I crop an image to the centre with ImageMagick?

Use -resize with the caret suffix to cover the target box, then -gravity center -extent to trim: magick in.jpg -resize '400x400^' -gravity center -extent 400x400 out.jpg. This works even when the source is smaller than the target.

What does +repage do after a crop?

It discards the virtual canvas offset that cropping leaves behind. Without it, formats that store an offset such as PNG and GIF remember the original page geometry, so later operations land in the wrong place.

Why does -trim do nothing on my image?

-trim only removes a perfectly uniform border. Real photos and scans vary slightly, so you need a tolerance: add -fuzz 8% before -trim.

How do I split an image into multiple tiles?

Give -crop a size with no offset and use an output filename containing a counter: magick in.jpg -crop 400x400 +repage tile_%02d.jpg

ImageMagick crop command generator

Generate ImageMagick crop commands: crop at x,y, centre crop to a size, crop to an aspect ratio, slice into tiles, or auto-trim borders. Explains why you need +repage.

ImageMagick's -crop does four quite different jobs depending on how you call it, and it leaves behind a piece of hidden state — the virtual canvas — that causes most of the confusion people run into afterwards.

Crop a rectangle at a position

magick input.jpg -crop 400x400+100+50 +repage output.jpg

The geometry reads WIDTH x HEIGHT + X + Y, measured from the top-left corner. The origin is +0+0.

Centre crop to an exact size

A bare -crop is the wrong tool if the source might be smaller than the target — you would get an image smaller than requested. Scale to cover first, then trim:

magick input.jpg -resize '400x400^' -gravity center -extent 400x400 output.jpg

This always produces exactly 400×400, never distorts, and works on any input size. Change center to north to bias the crop towards the top — useful for portraits, where centre-cropping tends to cut off heads.

Crop to an aspect ratio

magick input.jpg -gravity center -crop 16:9 +repage output.jpg

ImageMagick 7 accepts a ratio directly and works out the largest matching rectangle. ImageMagick 6 does not support this syntax — on IM6, use the centre-crop recipe above with explicit pixel dimensions.

Slice one image into a grid of tiles

magick input.jpg -crop 400x400 +repage tile_%02d.jpg

With no +X+Y offset, -crop cuts the whole image into a grid. Your output filename must contain a counter such as %02d, or every tile overwrites the previous one. Inside a Windows .bat file that counter has to be written %%02d.

Auto-trim a uniform border

magick input.jpg -fuzz 8% -trim +repage output.jpg

-trim on its own almost never works on real photographs or scans, because the border is never a perfectly uniform colour. The -fuzz tolerance is what makes it usable — start around 5–10% and raise it until it catches.

Why you need +repage

Cropping does not really remove the surrounding area; it records an offset into a "virtual canvas" that remembers where the crop came from. Formats that store an offset — GIF and PNG — keep that information, so:

Your cropped PNG may render with unexpected padding.
A later -composite or -extent lands in the wrong place.
identify reports a page geometry that does not match the pixel dimensions.

+repage discards that offset. Add it after every crop unless you specifically need the canvas preserved.

Crop and resize in one pass

magick input.jpg -crop 1200x1200+200+100 +repage -resize 400x400 output.jpg

Order matters: operators run left to right, so this crops first and then scales the result.