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Recently I created a website where I sell books. I captured some images with a Canon EOS 550, and then I resized them according to the website space, but when I resized the original picture, then the title of the books became blurry. How I can make my pictures look clear and readable?

enter image description here resized image

enter image description here original image

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The ending to that book is captivating, love it! – dpollitt Apr 6 '13 at 14:48
up vote 11 down vote accepted

First of all you need to use a good resize algorithm for that case. Lanczos, or Photoshop's Bicucbic optimized for reduction. And then to make for better contrast around the letters you can use some output sharpening.

Secondly, there is a minimum resolution you can use to render the fine letters. The book is a perfect example because of the different fonts and sizes.

Below is bicubic on the left, lanczos on the right, in two different sizes (10% and 20%). You see that lanczos separates letters like I better than bicubic. You can read the top line in the smallest image with lanczos but not with bicubic. Also twentieth edition is better rendered with lanczos. Also the 2013 is prettier rendered, albeit readable.

book too small

You need to make the image bigger to read the bottom lines. Again, lanczos renders I's with more "Air" to the letters around them. The differences are subtle, but may have big impact in the long run if a person really wants to read more text like this.

book bigger

Lanczos also allows you to resize books and pages with fine texture with less chance of causing fake texture (moire).

A 3rd thing to note is that the results I posted are based on a jpeg compressed source, which I then saved as jpeg again, and maybe S.E. recompressed it again. If you keep everything in raw (tiff/bmp/ppm uncompressed) until the last moment and then use a subtle compression (maybe even lossless) you will also improve the readability.

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I'm stunned, that is so awesome. Wish I could upvote you twice. – Paul Cezanne Apr 6 '13 at 15:46
Yeah, +1; it's the same thing I said but the illustrations really make a difference. :) – mattdm Apr 6 '13 at 16:30
Also a tip: to keep the service SE uses for image hosting from recompressing, upload PNG files instead of JPEG. For little sample files and similar, they're not muh bigger so there's no real downside. – mattdm Apr 6 '13 at 16:32
fantastic illustration! – Regmi Apr 6 '13 at 16:46
nice to know about png :) – Michael Nielsen Apr 6 '13 at 16:53

Although it's very clear in the sharp lines of letters, this actually happens to all detail when a digital image is resized.

The algorithms used to shrink an image interpolate information from the surrounding pixels. This prevents artifacts like jaggy lines (aliasing, in computer graphics terminology), but introduces blur. The easiest approach is to run a sharpening filter (like unsharp mask, which sharpens, despite the name) after resizing down.

Some filters are also better than others for different purposes. You are probably using a default like Bicubic. For downsizing, try Lanczos instead (this shoul be in the resize image dialog box, maybe under advanced).

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