RePix is described as 'helps you in batch resizing any image into a preset resolution and save it easily and quickly. This is the quickest way one can batch resize a large number of images at once' and is an app in the Photos & Graphics category. There are more than 10 alternatives to RePix for a variety of platforms, including Windows, Mac, Linux, PortableApps.com and Xfce. The best alternative is IrfanView. It's not free, so if you're looking for a free alternative, you could try ImageMagick or qimgv. Other great apps like RePix are XnView MP (Free Personal), FastStone Image Viewer (Free Personal), XnView (Free Personal) and QuickViewer (Free, Open Source).
FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor. It has a nice array of features that include image viewing, management, comparison, red-eye removal, emailing, resizing, cropping and color adjustments.
ImageMagick is a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (about 100) including GIF, JPEG, JPEG-2000, PNG, PDF, PhotoCD, TIFF, and DPX.
QuickViewer is a graphic image viewer for comfortable browsing of many images. This software performs reading of image data in advance. And drawing the imported image data on the screen with OpenGL. You can browse images with much smoother response than ever before.
A new image viewer that has nice features like identifying and generating colors from image, changing colors of image with color adjustment and color matrix tools, crop & split image for Instagram, TIF/GIF Animated extractor, batch functions.