You can add files/folder by either using the built in buttons or can just drag-n-drop as well. True its main window looks simple, but under its “options” pane (to the right-side), you’ll find a reasonable amount of options too.
Few main features …
*. Shows info about the added images such as their name, resolution, image type and the path (you can also get the “properties” window by right clicking on each image).
*. Change the output/”save-to” folder.
*. Change the output image resolution manually by entering the numbers or you can use built in “presets” (iPod, iPhone, Facebook, DVD NTSC/PAL etc) and can also use a “percentage” values (came in handy for my needs :)).
Make sure to select the proper setting from the “Resize by” option first (whether you’d like to use the “Percentage”, “Preset Size” or “Custom Size”).
*. Enable/Disable keeping the aspect ratio.
*. Switch between several image resizing (scaling) algorithms such as: lanczos3 (default), Linear, FastLinear, Bell, Bilinear etc.
*. Add a “watermark” and configure settings such as its opacity and the position.
*. Converts into other image formats (including adjusting their quality based settings) JPG, PNG, BMP, GIF and TIFF.
*. Enable/disable batch renaming (can give a custom name, of course).
*. Add few image enhancement filters such as: Rotate, Flip, AutoSharp, Colorize (change Hue and Saturation), adjust Brightness/Contrast/Saturation and add “Round” effect to image (beware that high values will take a reasonable amount of time to process).
*. Once you’ve made the changes, just click on the Green looking “Play” button which should process the images (also shows you an output).