How I improved my workflow with Imagemagick

Published on: February 25, 2015

When working with assets you will often want to change some of them. My personal experience is that I often want to resize images, stitch them together, blur them or convert them from .png to .jpg. When I had to do this I usually sighed, fired up Photoshop, created a batch and then ran everything in my folder through that batch. When I realized I got it wrong I would have to do this again and Photoshop usually crashed at least once in the process as well. Needless to say, I did not enjoy adjusting my assets. Until I didn't have Photoshop anymore...

Changing workstations

In december I switched from an OS X oriented workplace to an Ubuntu oriented workspace which meant that I didn't get to have Photoshop on my machine (without jumping through hoops). This wasn't a problem because I didn't have to work with assets as much as I used to and when I did I would just ask somebody else to do the tedious tasks for me.

But then I remembered Imagemagick. In the past I've used their PHP library to resize images on my webserver, but under the hood that actually uses the Imagemagick command line tool. And since I was working with a Linux machine I figured I could install Imagemagick and use it. And so I did. And it's beautiful.

Start using Imagemagick

Before you can use Imagemagick you have to install it, go to their install page and find the appropriate version for your machine. Surprise, it turns out they have an OS X version as well. After you've installed Imagemagick you should prepare some images to resize.

Resizing images

Resizing images is surprisingly simple. Open up a command line, navigate to the folder where you have your image and type this into your command line.

convert myimage.jpg -resize 50% myimage_half_size.jpg

This will scale your image down to 50% of it's original size. If you have several images to do this with you might run something like:

for "x" in *.jpg; do convert $x -resize 50% half_size_$x; done;

Pretty simple, right? You can also scale images proportionally to a pixel value like this:

convert myimage.jpg -resize 250x myimage_250.jpg

This will make the image 250px wide and scale the height proportionally. Scaling an image based on height is similar but place the pixel value after the x:

convert myimage.jpg -resize x250 myimage_250h.jpg

Manipulating image quality

After resizing your images you might want to optimize their quality a bit as well. I usually get extremely high quality assets and they can be as large as 2-3Mb sometimes. After resizing they might already be around the 100Kb, but giving up a little quality can take them down to 60-70Kb. Here's the command to do that:

mogrify -quality 60 myimage_lq.jpg

Instead of convert I used mogrify for this snippet. Mogrify is used for in-place manipulating of images, so it overwrites your image. If you don't want this you can just substitute it with convert and use it just like you did earlier.

Wrapping it up

With the commands you've learned in this post it should be easy enough to optimize and manipulate your images in the command line. For more examples check out the usage section on the Imagemagick website. I personally feel like using Imagemagick has improved my workflow and I hope it can (and will) do the same for you.



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