Resize Photos for the Web
You can check if your photo needs to be resized in Windows itself. Open the folder which contains the photo. Select the photo (by left-clicking the name of the photo) and its size appears in the grey status bar below. Neither the width nor height of the photo may exceed 800 pixels. When you do not see the grey status bar you have to click on the status bar in the View menu at the top of the folder.
What is a good size?
The best size of an image will depend on how you plan on using it. A&S Computing Drupal 7 sites are 960 pixels wide, so that is the widest image you would need in a Department, Program, or Center website. If you are floating an image in the text of a page with the text wrapping to the right or left, generally you want the image to be 200 - 300 pixels wide.
Image files types for the web
Most images on the web still fall into one of three types:
JPG (or JPEG) = use for photos and images with a lot of different colors but no transparency.
PNG = use for images with transparent backgrounds. Not rendered correctly in some older browsers like IE 6.
GIF = not recommended. png is better. Never use for photos since the max number of colors is 256.
Note: JPG and JPEG are the same image type. At one point some companies decided on three letter file extensions while others used four.
Resizing versus Cropping
When saving images for any purpose, you will hear two major terms for changing the size of an image: resizing and cropping. Resizing changes the size of an image while keeping the same height to width ratio. If you started with a rectangular image and you resize it to make it smaller, you will still have a rectangle with the same ratio, not a square.
If you need an image to be an exact set of dimensions, you will probably need to crop it. Cropping removes portions of the image and can change the width to height ratio.
You will generally use both of these methods if you need a series of images that are all exactly the same size (e.g. images in a slideshow, profile photos of faculty).
Note: you should very rarely make an existing image larger. An image only contains so much information, and if you enlarge an existing image, it will often look fuzzy or pixelated.
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