Downsizing Images in IrfanView
You can download the latest version of IrfanView from: http://www.irfanview.com/
This is a brief summary of the IrfanView downsizing process using IrfanView V3.99. It assumes that you have previously edited the image including cropping, color correction. Further it assumes that you have the image open and ready for downsizing.
1) Click "Image -> Resize/Resample...":
The "Resize/Resample image" window opens:
2) Select a new size from the "Set new size:" selections or select an option in "Some standard dimensions:". I chose "800 X 600 Pixels". Unless you have a VERY slow computer, ensure that the "Resample (better quality). Also, select "Preserve aspect ratio". For speed, select "Apply sharpen after Resample". Click OK. Notice that the window is now smaller.
3) Click "Image -> Information" to get the info:
Notice that the image size has changed.
4) Click "Image -> Decrease Color Depth..." and select 256 colors:
5) Click OK. Notice that the image quality hasn't decreased much. You wouldn't want to do this for printing, but it's fine for publishing to the Web.