Get and Set image dimensions

• Get dimensions: resizr -i <image-file>
• Set width and maintain aspect-ratio: resizr -i <image-file> -w <width> -o <output-file>
• Set width and height: resizr -i <image-file> -w <width> -h <height> -o <output-file>
• Help: resizr --help (Note: -h flag is for --height)