Adjusting the size of a digital image is called scaling. There are lots of tools for scaling images. This post tells how to scale images with GIMP, a free, cross-platform graphics editor that some folks call the “poor man’s Photoshop.”
Scaling an image for the web involves two tasks:
Downsizing your image
Since digital photos are often very large, they need to be downsized for web use, not only to make them fit properly in a page layout, but also to make them load faster. (Large images can really slow down the loading speed of a web page, and if your pages don’t load quickly enough, impatient viewers may leave your website.)
Adjusting the Resolution of Your Image for Web Use
The resolution of your image needs to be adjusted downwards to insure fast loading times for the web. Think of resolution as an index of the data density of a file. Web images don’t require as high a resolution as printed images do, or ones projected on large screens. Seventy-two DPI is plenty for web images viewed on a computer or other small screen device. Increasing their resolution over that figure will not increase their clarity one bit.
So, now that you know why you need to scale web images for the web, here’s how you do it with GIMP:
How to Scale Images and Set Their Resolution with GIMP
- Launch GIMP and open the image you want to scale in the editing window.
- Under the “Image” menu at the top of the window, select “Scale Image”.
- Make sure that the link symbols are joined, not broken. This will preserve the proportionality of your image (the ratio of its width to its height).
- Set the x and y resolution at 72 DPI.
- Set the largest dimension of your image at from 400 to 600 pixels to make a large web image, or 250-350 to make a medium sized one, or 100-200 to make a thumbnail. (Don’t worry about the lesser dimension of your image. It adjusts automatically when you set the larger dimension, provided the link symbol was joined when you made the entry.)
- Under the File menu, select “Save As”. Name the file whatever you wish and save it as an .xcf file (the standard GIMP image format).
- To convert that .xcf image to another format, under the File menu select “Export”. This brings up a window for saving the exported file. In the small window that says “all images” access the drop-down menu and select the format you wish. Web images are most often saved as .jpeg or .jpg files, but they may also be saved as .gif or .png. In another CyberKenPost I’ll explain the advantages of each of these formats. At any rate, you’ll be safe always to save your web images as .jpeg or .jpg files.