You can try Boxoft Batch Photo Resizer to resize image files, it provides 4 kinds of processing method: "Restrict width", "Restrict height", "Fit image" and "Ingnore proportion". it also allows you to rename, rotate, etc pictures. you can also switch images to other formats: tif, bmp, gif, jpg, ico, j2k, png,tga, pcx, etc.
More detail follow steps below: