Question

0

convert with bash - trim/crop and center

rated 0 times [ 0] [ 0] / answers: 1 / hits: 1745 / 2 Years ago, thu, february 3, 2022, 10:59:47

i need a fast and reliable way to modify a lot of images.
There is a lot of white around my pictures i want to get rid about.
The problem is, it is a number of similar pictures, but they have different sizes.
An example is here: a link My pictures have only the red and blue part and a huge white space around them.
I want pictures with the same format and less white space.

First i would need the maximum dimension of the non-white part of all pictures and then crop all pictures to the format of the biggest dimension. But the center of the image has to stay the center.

Is this somehow possible with convert or any other command line tool?

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

peratingcit

Add To Favorites

Follow

Total Points: 253

Total Questions: 122

Total Answers: 94

Location: Botswana

Member since Sat, Jan 7, 2023

1 Year ago

answered 2 Years ago serveeel · Accepted Answer

Okay, after an other hour of google i came up with my own solution.
In this link there is a script that goes through all images and crops them while the center stays the center.
Now i have my cropped pictures.
With

ww=`convert -ping "$f" -format "%w" info:

And cycling through all ww values for all pictures i get wmax.

wmax=`convert xc: -format "%[fx:max($ww,$wmax)]" info:`

With that and several loops

 convert $f -gravity center -background white -extent ${wmax}x${hmax} ${f}-canvas.png

I get the results. It is not nice, i crop one more time than necessary but it does the job and i have to finish my thesis.

    #!/bin/sh

    # gives the largest x and y values of all  png files in directory and puts them in the center of a canvas. This canvas is 10px*10px larger than the largest png file.



    # We cycle over all pngs to get maximum w and h

    for f in *.png

    do

      echo "Processing $f file..."

      # take action on each file. $f has current file name

    wmax=0

    hmax=0

    # width

    ww=`convert -ping "$f" -format "%w" info:`

    #echo $ww

    # height

    hh=`convert -ping "$f" -format "%h" info:`

    #echo $hh

    wmax=`convert xc: -format "%[fx:max($ww,$wmax)]" info:`



    hmax=`convert xc: -format "%[fx:max($hh,$hmax)]" info:`



    #  centertrim $f

    #  rm $f

    #  mv $f.out $f

    done



    echo $wmax

    echo $hmax

    wmaxp10=$(($wmax + 10 ))

    echo $wmaxp10

    hmaxp10=$(($hmax + 10 ))

    echo $hmaxh10

    # now we cycle through all pictures and add them to a canvas with $wmax+10 $hmax+10

    for f in *.png

    do

      echo "Processing $f file..."

      # take action on each file. $f has current file name

    echo convert $f -gravity center -background white -extent ${wmaxp10}x${hmaxp10} ${f}-canvas.png

    convert $f -gravity center -background white -extent ${wmaxp10}x${hmaxp10} ${f}-canvas.png

    #  centertrim $f

    #  rm $f

    #  mv $f.out $f

    done