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Script-fu example 10: Resizing images and keeping the aspect ratio

The following function resizes an image while it preserves its aspect ratio. This is different from the function resize-image which only resizes the image but doesn't keep the aspect ratio. (See also resize-image-keep-ratio.
resize_image.scm
(define (resize-image-keep-ratio filename-in filename-out new-width new-height)
  (let* ((image      (car (gimp-file-load RUN-NONINTERACTIVE filename-in "")))
         (drawable   (car (gimp-image-active-drawable image)))
         (cur-width  (car (gimp-image-width image)))
         (cur-height (car (gimp-image-height image)))
         (ratio      (min (/ new-width cur-width) (/ new-height cur-height)))
         (width      (* ratio cur-width))
         (height     (* ratio cur-height))
        )

     (gimp-image-scale image width height)
     (gimp-file-save   RUN-NONINTERACTIVE image drawable filename-out "")
  )
)

c:\> start gimp-2.2.exe -d -i -b  "(resize-image-keep-ratio \"c:\\temp\\ex_10.jpg\" \"c:\\temp\\ex_10_resized.jpg\" 100 100)" "(gimp-quit 0)"
See also other examples