How to resize an image with ImageMagick

Image files often need smaller pixel dimensions before they fit a web page, email attachment, CMS field, or release package. ImageMagick can write a resized copy from the command line while leaving the original available for comparison or another export.

The -resize geometry in the example uses a 600x400 box. When the source has the same 3:2 ratio, the output reports exactly 600x400; if the source ratio differs, ImageMagick preserves proportions and fits the result inside that box instead of stretching it.

Use ImageMagick 7 magick syntax when it is available. Keep the output filename different from the input while checking dimensions and visual quality, and use magick mogrify only for deliberate overwrite batches.

Steps to resize an image with ImageMagick:

Open a terminal in the directory containing the source image.
Check the source image dimensions before selecting the resize geometry.
```
$ magick identify -format '%f %m %wx%h\n' source.jpg
source.jpg JPEG 1200x800
```
Use a geometry that matches the intended destination. A 600x400 resize keeps the image inside a 600-pixel-wide by 400-pixel-tall box while preserving aspect ratio.
Write a resized copy with -resize.
```
$ magick source.jpg -resize 600x400 resized.jpg
```
ImageMagick reads source.jpg, applies the resize operator, and writes resized.jpg as the destination file. The source file remains unchanged because the command names a separate output file.
Verify both image dimensions.
```
$ magick identify -format '%f %m %wx%h\n' source.jpg resized.jpg
source.jpg JPEG 1200x800
resized.jpg JPEG 600x400
```
The resized file should report the target dimensions when the source and target aspect ratios match. If it reports a smaller width or height, the input ratio did not match the target box.
Open the resized image before replacing an asset reference or sending the file onward.

Use a geometry such as 600x400! only when distortion is acceptable. For a fixed output frame without stretching, resize and then crop or extend the canvas in a separate, explicit workflow.