With the StardewZem 1.1.0 - Very Easy XNB Merger, you can easily merge xnb files into your game without the hassle of using other image editing tools.

This tool supports all the major platforms.

How to use this mod:

If you want to download the xnb file, you need to click "Select" button.

Then, you will be able to see all the files.

You can also set the image size.

To select the images to be merged, you need to drag the image you want to merge.