Maintain cnavas aspect ratio

[leupi]

I am resizing lots of images with varying aspect ratios. The resized images all need to be 192x128, 384x256, and 768x512 (which all are the same aspect ratio). Most of the original images share that ratio; although, some do not. If I resize a 400x400 image to 196x128 it actually becomes 128x128, which makes sense. Is there a way to have a 32 px border on both the left and right added to maintain the 192x128 ratio? Of course this border would need to be larger or smaller, top and bottom, left and right, depending on the original image ratio.

Thanks,
Todd

[Bonzo]

You do not say how you are using Imagemagick and you would need to do some calculations on the image to find out the size of the image so you know which border/canvas to use.

Code: Select all

\( input.jpg -resize 250x250 \) -size 300x250 xc:black -gravity center +swap -composite 

This will resize an image to 250x250 maintaining the aspect ratio and place it in the center of a 300x250 black background.

[anthony]

See IM Examples, Thumbnails, Padded Images
http://imagemagick.org/Usage/thumbnails/#pad
which has many methods.

The Composite method is the oldest, most logical, and slowest

The extent method should be the fastest and simplest.
It even works for "resize to fill space", using the new '^' resize flag.

convert image400x400.png -resize 196x128 \
-gravity center -background black -extent 196x128 \
padded_image.png

PS: using a '@' flag will let you get a mix between "resize to fit", and "resize to fill", but the number of pixels needs to be calculated!

I feel a new IM example comming on!
See http://imagemagick.org/Usage/thumbnail/#bestfit
in a couple of days.

[fmw42]

see my script, aspect, at

http://www.fmwconcepts.com/imagemagick/index.html