If your work involves editing images, you’ll agree that there are times when you have to perform a single operation on multiple images. One such operation is batch resize of images. While most image editing software is capable of resizing multiple images in one go, it’s not always easy to find and use the feature, especially if you’re new to the application you’re using.
And that’s precisely one of the reasons why we’ve been publishing tutorials that help you learn how to perform a batch resize using popular image editing apps – see our tutorials for Converssen and Phatch. Expanding the lineup, in this article we will discuss how you can perform the operation using gThumb.
Note: all explanation is based on gThumb version 3.4.3, with the underlying OS being Ubuntu 16.04.
Steps involved
Given that the tutorial is centered around gThumb, you’ll have to first make sure you have the application installed on your system. If not, you can easily download/install it from Ubuntu Software Center (or GNOME Software if you’re using Ubuntu 16.04).
Once you are done with the installation part, open the set of images (that you want to resize) in gThumb by selecting the images (by pressing “Ctrl + A”) and then selecting “Open With -> gThumb” from the right-click menu. For example, here’s a screenshot from when I opened the image set in gThumb on my system.
Now, select the images (using “Ctrl + A” or through the mouse) so that a batch operation can be applied on them.
The next step is to open the “Tools” menu and select the “Resize Images…” option.
This should open a small “Resize” window containing various settings that you can tweak before the batch resize operation is performed.
Let’s understand these settings one by one.
1. You can enter the new dimensions in the “Width” and “Height” text boxes. What’s worth mentioning here is that by default these values are in percentage – 100% means no change to the dimensions have been done yet. Now suppose you want to reduce the width and height of the images by half. For this you can change the respective values to 50 – this means the dimensions have been reduced to 50%. However, more often than not, we don’t work with percentages when dealing with images – we work with pixels. So you should toggle to “pixel” in the menu that currently displays ‘%,’ and then apply your changes.
2. It’s easy to mess up the aspect ratio (and not to mention it’s time consuming as well) if, for example, you are manually calculating the height after changing the width to a certain value. So make sure to tick the “Preserve original aspect ratios” check-box until, of course, you have a compelling reason to decide otherwise.
3. In the “Destination” section, as you’d expect, you can specify the target directory (where resized images will be stored).
4. And finally, the “Format” section lets you specify the format of resized files. Available options are JPEG, PNG, TGA, and TIFF.
Here’s the Resize settings that I used.
Now, just click the “Execute” button, and the resize operation will be executed based on the settings you’ve applied. Once the operation is done, gThumb will display the contents of the destination folder (or in other words, resized images).
Conclusion
While gThumb is basically an application to view and organize images, it lets you do some basic editing work as well. In terms of batch file operations, aside from resize, the application also allows you to rotate images, change their format, and play with their metadata.
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Himanshu Arora
Himanshu Arora is a freelance technical writer by profession but a software programmer and Linux researcher at heart. He covers software tutorials, reviews, tips/tricks, and more. Some of his articles have been featured on IBM developerworks, ComputerWorld, and in Linux Journal.
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