How to Resize and Make Images Larger without Losing Quality?

Resize and Make Images Larger Without Losing Quality?

I suppose you’ve noticed that when you resize an image to make it larger this results in a loss of quality. The enlarged image looks blurry, pixelated and amateurish. Shrinking images to load quickly on your website or Facebook is generally not a problem.

• Pixelation (or pixellation in British English) of an image. Having pixels that are large enough to be individually visible from a normal viewing distance.

So is it possible to make images larger without losing image quality? In this article, I will show you how to resize images to make them larger without losing (too much) quality, but in reality, no matter what trickery you use an image will always degrade to a certain extent.

What is Pixelation?

Pixelation is caused by displaying an image at such a large size that individual pixels, (small, single display elements that comprise the image), are visible. Such an image is said to be pixelated.

• If you’re old enough you may remember the early video games which ran at very low resolutions with easily visible pixels.

 

Pixelation is particularly noticeable with curved objects and diagonal lines which gain an unnatural appearance.

There are tricks to reduce the effects of pixelation such as using anti-aliasing to smooth the appearance of low-resolution images but this little bit of trickery is no substitution for higher resolution images.

Why Images Lose Quality When Enlarged?

All your digital images, i.e. BMP, GIF, JPEG, PNG, TIFF, etc., are made up of thousands of pixels, generally know as bitmap-based images. If you zoom in you can actually see those pixels as squares.

When you use an image editing application such as Photoshop or GIMP to resize the image the software will attempt to shrink or enlarge these pixels to resize the image.

• Note: You cannot actually shrink or enlarge a pixel. To ‘shrink’ a pixel the software simple removes pixels in an ordered manner so reducing the number of pixels in the image. To ‘enlarge’ a pixel, the software simply duplicates the pixels so increasing the size of the image.

This is why when you reduce the size of an image there is little to no visible quality loss. On the other hand, when you make an image larger, the now enlarged pixels become more visible, making the image look pixelated.

Vector Based Images

All image files can be categorised into either bitmap-based or vector-based files.

Unlike bitmap-based images, vector graphics are not made up of a grid of pixels and are more suited for illustrations that require precise measurements. They are also easily scalable due to their mathematical nature. However, the vector-based file format has its drawbacks as well. It is not good for displaying photo-realistic images such as a photograph because images of this type generally do not contain well-defined shapes and curves.

How to Resize and Make Images Larger Without Losing Quality?

What’s needed is a method to compensate for each enlarged pixel by matching the properties of its neighbouring pixels. This method is called Fractal Interpolation. Using this technique to enlarge images will produce much better results than other methods.

• In fractal interpolation, an image is encoded into fractal codes via fractal compression and subsequently decompressed at a higher resolution. The result is an up-sampled image. Fractal interpolation maintains geometric detail very well compared to bilinear interpolation or bicubic interpolation.

Here is how to use fractal interpolation using GIMP, though the same technique can be used in most common image editing software.

Resize Images Using GIMP

GIMP is a free imaging application usually considered an alternative to Adobe Photoshop. It is an excellent solutions for enlarging your images with minimum quality loss. Here is how to make images larger using GIMP without losing quality.

Open the image you want to resize in GIMP. Go to Image > Scale Image and enter your required dimensions. Under the Quality section choose Sinc (Lanczos3) as the Interpolation method and click the Scale Image button.

The following images show a section of the butterfly image (100 x 50) scaled up by a factor of 6 to (600 x 300) with and without Lanczos3 interpolation.

That’s it, you can now export the image for the web or wherever you need it.

Conclusion to Resizing Images Without Losing Quality?

A final piece of advice. The image formats used on the web, JPEG etc., are based upon compression algorithms which are not “lossless”, that is they are “lossy”. This means that every time you save the file you lose more of the original data. To prevent this always save your original images in a lossless file format such as PNG or TIFF. Edit that file to your hearts content, then save the production file in the JPEG or other format you require.

If you’re really interested in quality photography you might like to take a look at some Trick Photography And Special Effects or ShutterStock.

Finally, just remember that every time you open, edit, then save a JPEG etc. file, whatever compression settings your graphics editing program has been set to will “recompress” that file so potentially reducing quality.