With Photoshop, the picture
Okay, so here's the process. After searching high and low on the net, it's so far the best and easiest tutorial I found (for beginners :), with simple instructions, large picture samples with red circles and comments: designboom.com/optmize_tutorial.html
Remark: this method is for posting pictures on the web.
- Under Image Size, set the resolution to 72 pixels/inch;
- Then, set the size to maximum width 600 pixels x maximum height 800 pixels;
- Finally, under File, select Save for Web (I kept quality to 100% though).
The same image, using Photoshop... notice that the image is much clearer, i.e. image quality almost intact. You can see the difference if you look at Chicken Little's feet... they are blur in the picture above.