Manipulate Images from Linux Terminal
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Manipulate Images from Linux Terminal

Image manipulation through Terminal

·2 min read
Contents

One of the simplest ways to modify images from terminal in Linux is with ImageMagick utilities. To install ImageMagick on debian/ubuntu, run sudo apt-get install imagemagick.

ImageMagick tool can perform many operations on images. Here we will go over just a few:

Converting image format

One of the simplest things you can do with images is convert the format. Here we will modify a PNG image to a JPG.

bash
# PNG file we are operating on
$ file a.png
a.png: PNG image data, 553 x 302, 8-bit/color RGBA, non-interlaced
# command to convert from PNG to JPG
$ convert a.png b.jpg
# output JPG file
$ file b.jpg
b.jpg: JPEG image data, JFIF standard 1.01, resolution (DPCM), density 38x38, segment length 16, baseline, precision 8, 553x302, frames 3

Resizing

There are multiple ways to resize an image with ImageMagick like increase the image size by hight while keeping aspect ratio. One of the simplest ways is to pass a -resize flag with the new dimension.

bash
# file we are operating on
$ file a.png
a.png: PNG image data, 553 x 302, 8-bit/color RGBA, non-interlaced
# command to resize
$ convert a.png -resize 1106x604 b.png
# resized image
$ file b.png
b.png: PNG image data, 1106 x 604, 8-bit/color RGBA, non-interlaced

Rotating

To rotate an image by some degree, just pass the value with the -rotate option.

bash
# rotate image a.png 180 degrees and save the modified image as b.png
$ convert a.png -rotate 180 b.png

Chaining multiple operations

convert command can accept multiple operations at a time so we could convert image format, resize and rotate an image all in one command.

bash
# original a.png file
$ file a.png
a.png: PNG image data, 553 x 302, 8-bit/color RGBA, non-interlaced
# all three commands chained
$ convert a.png -resize 1106x604 -rotate 180 b.jpg
# output file that is rotated 180 degrees, resized and converted to jpg
$ file b.jpg
b.jpg: JPEG image data, JFIF standard 1.01, resolution (DPCM), density 38x38, segment length 16, baseline, precision 8, 1106x604, frames 3

Notes:

  • If the input file and output files are named the same, then the original file will be overwritten.
  • Since we are working with Linux Terminal, convert utility can be used recursively on multiple images by going over images using a for loop.
#ImageMagick #Linux #Terminal

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