Resizing/shrinking .JPG files without losing quality?

Question

Im using Gimp to resize images. When using a high res image normally 4500 x 2994 i usually need to shrink this image to 325 x 130 pixels.

As you can imagine i loose the shiny, glossy and high res quality oof the image. Ive tried to save the image as .bmp and then resize it, this has made a slight difference but not a considerable change.

What else can i do to ensure i retain the hi-res quality of the image?

Thanks to anyone who helps.

Answer 1

Downsizing ultimately means that you loose information. You can only try to achieve a "good" result.

Here are three possible options that come to my mind:

• sharpen the image before downsizing

• cut out the most important part of the image

• downsize 50% several times instead of resizing once

Answer 2

I found that the from and to formats are incommensurable, that means you add a lot of extra-noise to the JPG noise:

• 2994 = 2 * 3 * 499
• 4500 = 2² * 3² * 5³

You may have better results when scaling by common factors, in this case 6:

• 4500/6 = 750
• 2994/6 = 499

I'd try a tool that is specialized for this kind of work, maybe ImageMagick will help you. This tool is aware of the JPG specificity and has options to control the output. If I'm right, Wikipedia uses it under the hood.

Answer 3

You're likely to find your best conversion comes when the main size reduction is by an integer factor. So, first choose a large intermediate size; for a 325 x 130 target, you might choose 12x this, or 3900 x 1560.

Now transform your source image into this size (3900 x 1560) by cropping and/or scaling. Depending on your needs, choose cropping over scaling, and when scaling prefer an integer-based factor (like 1/2 = 50.0%, preferably, or 21/40 = 52.5%) over an oddball factor (like 1560/2994 = 52.1%). You can usually manage with the "smoother" factor by cropping (or padding) before or after, e.g. after scaling a 2994-wide image by 21/40 to a 1572px-wide image, you could crop 12px off to get the 1560-wide image.

Finally scale the resulting intermediate 3900 x 1560 image into the target size (325 x 130).

Answer 4

When resizing using Gimp, there's that 'link' icon that you click to retain the aspect ratio of the image when you drag from a corner (not an edge). That's what I would recommend.

Answer 5

You should try and use a better software for that much shrinking. I am not saying GIMP is bad, it is a great software, but you might preserve the quality of the photo with a tool like this: http://www.paintshoppro.com/en/pages/jpg-file/