Imagine is an Open Source app for Windows and Linux that can compress JPEG and PNG files in batch with options for colors and quality.
By design, it has an attractive and very easy-to-use interface. You can drag-and-drop your images or click on add to select images. Double-clicking on any picture will open it to the size of the app and allow you to change the background color and a slider to determine quality. Above that slider, you can see the file size before and currently and the percentage change. At the top, you can also find a before and after button to quickly compare how your image looks.
If you decide to batch edit your JPEG or PNG pictures, it has all the features mentioned above except for the before and after viewing. Also, the options to clear all and three different save options (save and overwrite, save with new name auto, and export to) are available in batch mode.
If you're looking for a simple, effective, and free way to compress your images, Imagine has everything you need. Imagine is handy for email, web design, or just saving space.