You can never have too much resolution. I hate images that have been scaled down (the 100% worst is when websites review a camera, and post sample images that are 1/10 the original size.
Sure the average screen may have a resolution of 2-3 megapixels, that does not mean that you need to scale the image down. Computers have the ability to scroll around an image. Uploading as high a resolution as possible allows people to view more detail. For example, on both desktops and mobile phones, you can view this large image, and can see all of the cuteness, especially when you have the ability to zoom in. http/farm8.staticflickr.com/7372/13351430803_21a9254c3e_o.jpg
All the resolution the camera would make is a crucial point of a picture, despite the technical troubles with big megapixels. So if you need a resize the only reasonable way is to use some software 1) with Lanczos algorithm or 2) with a possibility of step-by-step bi-cubical resize, using slight unsharp mask between steps. All other ways are just a loss of details, sharpness and overall contrast.
Irfanview allows you to do batch resizing and renaming (and lots of other changes) at the same time for as many files as you want. Go to "File", "batch conversion/rename", choose the "save to" folder, add your files, and use the "Advanced" section of the batch conversion utility for resizing, flip, rotate, etc. Resize 1,000 pics in a few minutes.
And it's free and a 1.8 MB download. It has been around forever.
I agree, Irfanview is the best Windows software to quickly convert, resize, crop, arrange or calibrate your pictures.
I've been using it for ... ages And found nothing else better since the days of Win2000/XP...
Sure, the interface is not very "user friendly", but once you understand how it works the ability to do operate on large picture collections very fast is extremely powerful.
In all honesty, I resize just using MS Paint. It's cheap and basic and does a decent job as far as I'm concerned. I'm by no means an expert, just one of those millions of average users. Why spend money on something you already have the ability to do very quickly and easily? No-brainer to me.