Resizing

Warning

This article was written about seven years ago, and lots of techo things have improved considerably since then. But the basic facts haven’t changed, so this article is still quite useful for beginners. Please just bear in mind that any numbers are probably misleading in today’s world.

If you Google “Image resizing”, you will find many sites which do this for you, on line. Some of them give you lots of guidance in very simple English, some are more taciturn, but they all do the job.

If you Google “Image resizing downloads” you will find many free applications which will do the job on your computer.    I haven’t tried any of them, but this one appears to be quite good, and it runs on any version of Windows, from ’98 up to 7.   It’s only a 3 MB download, so you can have it up and running in no time.   If you use a Mac, Tocino says that the facility is built in – I’m sure he’ll be happy to tell you where to find it.

Doing the resizing

A Resize Window

Here’s a picture of the resize popup that appears in my old PaintShop Pro.   It’s probably quite similar to the one that appears in your image processing software.

Here you can choose three different ways to resize – by pixels, by percentage and by print size.

Near the bottom you’ll see a checkbox that is labelled “Maintain aspect ratio”.   If that is checked I can choose either to change the width, or the height, and the program will calculate the corresponding height, or width, automatically; and show me what it’s worked out.   Whatever width I choose, the aspect ratio of the picture will not vary.

Here I’ve chosen a width of 700 px, and PSP has worked out that the shrunken version of my image will have to be 467 px in height.

Now, see the drop-down box labelled “Resize Type”?   Let’s click on it and see what our choices are –

Resize Options

There are many mathematical algorithms that can be used to resize images, but generally speaking there are three available in ‘ordinary’ applications.

  • Pixel resize (also known as ‘Best neighbour’, or similar)
  • Bilinear, and
  • Bicubic

Forget about pixel resize, it’s terrible for most pictures; it’s ‘jaggy’.

The rule of thumb for the other two is –

If you’re making the image bigger, use bicubic; if you’re making it smaller, use bilinear.

This isn’t always correct, you may sometimes need to use bicubic when you’re shrinking things, in order to sharpen critical edges, but it’s a very useful starting point.

PSP kindly prevents me from having to remember which is which by offering me ‘Smart Size’.



Your image processing software will have similar facilities, and possibly a great deal more.   Boadicea’s Corel Draw and Corel Paint are very much the same.

If you do some further Googling, you’ll find lots of advice about making pictures the appropriate size for the purpose, and on not relying on browser resizing, for a variety of reasons.   So, don’t take my word for it, research it yourself. 🙂