How to Rescale Images in Digital Image Editors

Image editors display images as bitmaps -in other words, as grids of square pixels. When you want to add one image element to another, image pixels of one image will overlay those of the background. If the two images are not to the same scale (i.e. if the resolutions are not the same), they will not blend as intended.

Fortunately, you can rescale images to get over this problem. Here are examples of two dialogue boxes that appear when an image is rescaled – permitting both physical as well as pixel size changes.

Use the dialogue boxes to specify the size that an image will be when printed or displayed on a computer screen (via a website, for example). If the image is to be printed using a desktop inkjet printer, a resolution of 300 pixels per inch is usually sufficient. For screen images (which are limited by the resolution of the computer monitor), 72 pixels per inch is the conventional setting.

Such dialogues normally maintain the proportions (the ratio of height to width) of your image; change the width, and the new height will automatically be set. If you need to change the proportions (say to fit a photo frame aperture or a space on a web page), click on the Constrain Proportions button or Maintain Aspect Ratio (depending on the dialogue).

Now for a creative application of image combination: the use of one image to provide a border for another one. (There is no reason always to use plain colors for image borders.)

The idea of framing an image is to set off the subject to its best advantage: a frame should never compete for attention with the image. If your frame is too distracting, blur your framing image or, perhaps, mute the colors slightly.

For a different effect, use the original image, enlarged, as your frame. Blurring the image (or otherwise altering it) is now even more important to ensure differentiation.

  • Start with the original image. Perform any image edits on this that you wish to.
  • Open the second image, without closing the first. This will be your frame. Resize this such that it is (say) 30 per cent larger in both width and height. This will give you a 15 per cent border all around. Ensure that the image has the same resolution as the original.
  • Switch back to the original image and select the entire image. Choose Edit>Copy to copy this image to the clipboard.
  • Paste the copied image into the second image and position centrally.
  • Blurring has been applied to the frame to separate the images.


Don’t change sizes too many times using the same image or image element. Each time an image is resized, pixels will be interpolated (that is, pixels are created based on the average color values of adjacent pixels) to create the image at the new scale.

When pixels are created in this manner (whether the process involves new ones being added or the total number being reduced), there is a detrimental effect on the sharpness and absolute resolution of the image: such images tend to lose critical sharpness. Though techniques exist to increase the perceived sharpness again, these cannot actually restore the information that has been lost.

Filed Under: Computers & Technology


About the Author: Justin Belden is a freelance web & graphic designer with over 15 years' experience. He is also an Avid member of the Design/Development community and a Serial Blogger who loves to help people by sharing interesting and informative tips and trick related to computer and technology.

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