All photo editing software will have a command for changing the pixel dimensions of an image. Look for a command called "Image Size," "Resize," or "Resample." When you use this command you will be presented with a dialog box for entering the exact pixels you wish to use. Other options you may find in the dialog are:
- Resample - You need this on when sizing down. This enables the software to change the pixel dimensions.
- Constrain proportions or keep aspect ratio - You want this option enabled. It prevents the image from being stretched and distorted. When this option is enabled, you only need to enter one value--height or width--and the other value will adjust automatically.
Never, ever resize and overwrite your original file!
After sizing the image, be sure to do a Save As so you don't overwrite your original, high resolution file. You'll want to save as a JPEG file.
- When choosing the compression level, keep quality in the medium to high range.
- You want to shoot for a file size of 30 to 100 KB per image. Go small if you will be putting several files on the same page or sending them in one email.
- Try not to exceed 100 KB per Web page for the total of all images.