36.30 Resize an Image

20190428 To re-scale (resize or reduce the size of) a photo (or any image) that might be too large for sending by email, for example, or too large to include in a presentation, we can simply specify a percentage, thus retaining the aspect ratio of the image:

convert -resize 25% img.jpg imgs.jpg

We can resize an image down to a size that will fit within the specified bounds, like 800x600. Depending on the aspect ratio of the original image, the resulting image will be exactly 800x600, or its width will be 800 or its height 600.

convert -resize 800x600 img.jpg imgs.jpg

If a single size is specified then either the width or the height is reduced to that size, which we can do in-place with:

mogrify -resize 800 img.jpg

To force a resize without retaining the aspect ratio:

convert -resize 800x600\! img.jpg imgs.jpg


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