People often send large photos via email. These file sizes are usually large, typically a few megabytes because they are taken from multi-megapixel camera. The more the megapixel, the larger the file size.

I prefer to reduce the image size before I email or post on the web, these file sizes are small (couple of 100 kilobytes) and typically occupy 10 percent the disk space of those taken directly from your digital camera. They are also easier to send/forward and you can send many of them at once.

I found a very nifty plugin for Nautilus called Nautilus image converter. Nautilus is the default file manager on Gnome (Linux/Unix Window Manager). Under Ubuntu, startup synaptic and look for nautilus-image-converter.

After installation, you need to either logout or re-start your PC for it to take effect.

Once loaded, you just need to right click on the image/s and resize them. You can select one or multiple files. By default your original image is not replaced, new image is created with the name: filename.resized.jpg (or whatever is the file type)

You can also replace your original image if you like and rotate them.

For those who prefer command line, you can install this package called imagemagick and use this tool called mogrify.