Compressing images - how to
With so many wonderful images being posted here, it's important to remember that, if they are too big, it will take a long time to download for those members with dial-up connections. No fun at all!
I'm going to post this in several forums - we should probably put together a FAQ on this, however that's done. Web graphics is a huge subject area, but it doesn't have to be all that complicated.
This is a lot of stuff - if you reduce the width of your browser window it may be easier to read.
Hopefully, you will find this helpful.
When images are scanned or downloaded from a camera, they are often in a high-resolution format that is unsuitable for the web (or for emailing) simply because they are too large or because they are of the wrong file format. (You do want a high resolution for printing purposes, though, so always, ALWAYS, keep a "good" copy before you do anything to an image)
There are many ways to enhance and improve images, depending on your skill with image editing programs but, most fundamentally, you may want to:
change to overall physical size of an image (how large it is on the screen), and
- add a little compression to reduce its file size (in kilobytes, this affects how long it takes to download).
How you do this depends largely on which program you have on your computer. Your camera or scanner may have come with some software, you maybe using Microsoft Image Editor, or you may have something more sophisticated, such as Photoshop or Photopaint. The "Paint" program that comes with Windows is not unsuitable.
So let's say you have an image of a pretty flower. Let's say it came off your camera at about the size of your visible screen and a megabyte in size (1,000kb). Way too big.
First, do what you will with your image (colour correction, sharpening etc). Then look at it critically to see if it could stand a little cropping to get rid of unneeded bits and pieces.
See the images below. One image might be selling a house, the other is about driveway paving. Decide what is important about your image and crop it down. (artistically, of course, keep composition in mind. Single items often look better slightly off-center, horizons generally don't go in the center of the image etc)
Now you've taken the first step toward reducing download time - your image is a bit smaller.
Now you can resize it: change the overal size of the image to something that fits comfortably onto people's monitor. Larger images tend to look nicer, but you will have to give up some impact for fast download.
Tip: Low contrast images tend to compress better into smaller file sizes than images with sharp contrast between light and dark areas. So if your image doesn't have a lot of strong colour changes or light/shadow, you can "afford" to keep it a little larger.
Also keep in mind...