Most of the application for image resize does the resizing keeping the aspect ratio and if you change the aspect ratio while resizing, the image becomes stretched. Photo3x2 is a freeware application to offer a quick method to change the aspect ratio of your pictures (by cropping the picture, not by resizing or stretching the picture). The tool supports most of the common image formats like jpg, gif, bmp, ico, tif, wmf, png.
You can either select predefined aspect ratios like analog camera, digital camera, wide screen etc or define your own custom ratio as well. The application does well in changing the aspect ratio. The only missing feature is bulk image aspect ratio change. You can only change one image at a time.
