In this tutorial we will teach you how to resize a picture in gimp using the content-aware resizing feature, also known as liquid rescale, without distorting it and preserving the features. This means that while resizing an image non-uniformly, the image won't get stretched out.
To work with this feature, we will download and install a plugin.
Download For Mac:
http://liquidrescale.wikidot.com/en:download-page-macosx
Download for Windows:
http://liquidrescale.wikidot.com/en:download-page-windows
For this tutorial, we will be working on a free stock image which can be downloaded from the following link:
http://www.freeimages.com/photo/1280039

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Step 1 -- Installing the plugin
Once you have downloaded the plugin, simply open up the installer and follow the installation process.
One thing you need to make sure is that you install the plugin in the right directory. You need to install the application in your C Drive, within the program files folder, where the Gimp folder is present. The content aware resizing feature will not work properly if the plugin is not installed in the correct directory.
Complete the installation process and move on with the process.

Step 2 -- Opening up the Liquid Rescale feature
With the plugin correctly installed, let's rescale the image. In Gimp, head over to the layer menu at the top and you will see the liquid rescale option appearing at the bottom. Simply click on that option and a new window will open up.
Over here, you will be required to create a new feature preservation mask. This will create a new layer in the layer panel where we will mask the features which need to be preserved. Once you click on the new button, a notification window will open up. Simply close the window to move on with the process.

Step 3 -- Configuring the liquid rescale filter
Once the liquid rescale window opens up again, move to the Output tab. Over here, open up the drop down menu next to the Output target option and select the new layer which was just created.
Also, make sure that the three options, namely, resize image canvas, resize auxiliary layer and output the seams, are all checked.
Now all you need to do is change the dimensions and increase the width of the image. For this tutorial, we have increased the width to 1240 pixels.

Step 4 -- Masking the areas to be preserved
After that, you will need to move the liquid rescale window down for the time being and select the new layer from the layers panel. After that, move towards the toolbox and pick up the brush tool. For now, we will select the green color from the color palette and start applying the brush over the areas of the image which we want to preserve while the content aware resizing is taking place. Even a rough masking would do the trick but it completely depends on the image you are working on.

Step 5 -- Applying the filter
Once done, bring the liquid rescale window back up again and click on the refresh button. You will see that the masking in the preview area. Simply click on the Ok button now and once the processing is complete, the image will be automatically resized.
Once done, you will notice how the width of the image has been changed without any distortion, preserving all the features we masked.
And that's it for how to resize a picture in gimp using the content-aware resizing feature.