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Printing pictures displayed on screen so that they look good turns out to be surprisingly difficult, if not downright impossible.

I would like to know the simplest way to print a small to medium image from a web page and have it print out as a crisp picture to fit an 8-1/2" by 11" sheet.

This is a simple question that, once we dig in, turns out to have both a very simple answer, and a fairly complex one.

The simple answer: you can't. Not most of the time, and not with what you're asking for.

The complex answer, of course is: it depends.

I get frustrated sometimes watching TV crime shows, mostly because I know too much. They frequently take significant liberties with what is, and is not, actually possible.

For example, a frequent scenario has a number of detectives looking at a blurry photo of a car in the distance, and the person in charge directs the resident computer guru to "enhance it". Perhaps even more than once. Like magic the blurry photo of the car in the distance gets crisper and crisper until the image can be magnified and the license plate easily made out. The cops identify the criminal and save the day.

"If a picture is blurry, it's blurry. If a picture has low resolution it has low resolution."

It just doesn't work that way. At least not the magical "enhancement" that they're talking about. If a picture is blurry, it's blurry. If a picture has low resolution it has low resolution. Yes, there are "enhancements", of a sort, but they all involve trading off other aspects of the image - typically decreasing the image fidelity in order to, say, increase contrast, change colors and the like.

But nothing of the sort that would take a small, blurry image and turn it into a large crisp one.

I mention all that because, in essence, that's exactly what you're asking for.

Let's use an example:

200 pixel wide puppy

This cute puppy is a 200 pixel wide image. On my screen it measures approximately 2 inches across, meaning that my screen is, roughly, 100 dots per inch, or DPI.

Now, if I want to print that picture on an 8 1/2 inch wide paper, using 8 inches as the printable area, that means the printing process will need to make that picture 4 times wider (as well as 4 time higher).

Here's a small portion of that image when magnified by 4 times:

Puppy Eye, magnified 4 times

You can see that the image is already starting to get a little blurry. It's the same image as displayed above, just magnified 4 times.

Sadly, we're not done magnifying.

Most printers print at resolutions of at least 300 DPI, if not much, much higher. The net effect is that if you print an image that is less than that (say our 100 DPI image above), then the printer (or your printing software) must also magnify that image again. In our case that's an additional factor of 3 times.

Puppy Eye, magnified 4 times, then 3 times

Now you can really start to see the details of jpeg compression as well as the increased blurriness of the picture. Again, this is the same picture we started with, and in fact if you were to take a magnifying glass to that original on your screen, you'd likely see something very similar to this magnified version.

The bottom line is that on-screen images rarely print in high fidelity. There's just no getting around the fact that you're magnifying a small on screen image, and printing it on a device with higher inherent resolution.

Now, there's one exception. And it depends entirely on how the web page was designed. And for reasons that will become clear, most web pages are not designed this way.

Our puppy, once again:

200 pixel wide puppy - or is it?

If you're on a slow internet connection, you may notice that this version of the picture was slower to display. It may also look slightly different than the same sized image earlier in the article.

The first image in this article is a 200x217 pixel image. This image is a 1153x1249 pixel image, but I've instructed the browser to display it in a 200x217 rectangle. The browser automatically resized the very large image to fit in the very small hole.

I've set it up so that if you click on that image, you'll see it in full resolution. Since the browser already had to download it to show you the smaller version, the larger version should display very quickly.

And this would be the exception. If an image on a web page is authored to use a high-resolution version that's downsized by the browser, then printing that image will likely use the high resolution version and give you a much, much better result:

Puppy Eye, magnified 4 times, then 3 times Puppy Eye, magnified 2 times

In this case the image still had to be enlarged to show the printed equivalent, but this time by a factor of only two, rather than 12.

The net result, of course, is a much sharper image when printed in a larger format.

And yes, I did print both in the course of preparing this article. I wish I could show them to you, but the example magnifications above definitely match the printed result - if anything the printed version of the 200 pixel image is worse, as the printer's magnification technique is apparently slightly different than I used to create the illustrations above.

The bottom line is that for a high resolution print resulting in a sharp, clear image, you need to begin with a high resolution image. Most web images are not high resolution in any sense. While 200 pixels wide might be very appropriate to view on screen, it's nowhere near enough for a high quality print, and there's no real way to get around that.

Article C3409 - June 7, 2008 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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6 Comments
Octav
June 10, 2008 12:20 PM

Mrh, I wish this article had existed several months ago. I needed to explain to a tech-scared girlfriend why an image that looks good on the screen won't look very good on paper. Oh, well.

Ron El
June 10, 2008 12:41 PM

There are apps such as Genuine Fractals and SmartScale that can increase the pixel densities with amazing results compared to the algorithms used in printers and image editors. Not to the extent depicted in the crime TV shows, of course.

Leo
June 11, 2008 3:48 PM

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

I had a friend point me at Genuine Fractals as well. (A
photoshop plugin,
http://www.ononesoftware.com/detail.php?prodLine_id=2 for
those so interested.) It's definitely an improvement over
most stock enlargement algorithms, but still - you can only
go so far taking a 2x2 inch image and enlarging it to 8x8
:-). (As another friend pointed out, that's a factor of 16
larger, if you measure surface area.)

Leo


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Famia
June 23, 2008 2:01 AM

Here is something you can try if you have a scanner

1.) Print the image as is or save it to your hard disk and print using your image editing software and turn print actual size on. It'll print a very small image on paper.

2.) Scan that image using a high DPI (above 800 dpi). Save it. Most software will allow you to scan only the picture if you print the whole page.

3.) Print that image and this time use scale to paper.

That should give you a better resolution in theory. Have not got a chance to try both as one but I have tried to do it separately, I have scanned a small image to a large dpi and it looks good. and print a webpage to paper and that looks as good as what's in the webpage.

The downside is:
- It involves 3 steps.
- Since you have to print the small image on good paper to obtain good scan of the image you would waste a good quality paper
- The high res image would be >10MB with a slow PC this would be hard to process.

Rondi Phillips
September 23, 2008 12:14 PM

Great article. I was so disgusted when my husband ordered a copy of the picture of me and my kids out of the newspaper, and my head was cut off just above the eyes. At least now I have a better understanding why that happened.

FeRD
November 7, 2009 12:50 PM

The method posted above by Famia, I'm sorry to say, isn't correct in its statement that it "should give you a better resolution in theory". That idea, in fact, is one of the most common mistakes people make regarding issues of digital images, DPI, and output size/resolution.

The basic problem with the method suggested is that it tries to create more detail than the original image contains -- which, as Leo correctly points out in the article, is impossible. Printing out an image and scanning it at high DPI will be no more effective than simply adding false "resolution" by resizing the image in an editing program. Either method will result in a blocky, low-detail image, like the ones Leo showed in his article. In fact, the scanner method is slightly worse, since the scanner is forced to re-interpret the individual pixel dots that make up your image's details.

Now, it's true: sometimes this "worse" can appear better. Re-scanning introduces small variations in the image, which can lessen the boxy "checkerboard" appearance of the resulting scan -- this may produce the appearance of a more detailed image. But all that's been done is to "break up" the visible pixel grid-lines randomly, making them less obvious. You can get the same or better results by simply resizing the image in an app like the Gimp or Photoshop (producing "false" resolution), and then applying a slight blurring filter or other distortion effect to smooth out the image's blockiness. There's no benefit to printing and re-scanning an image that isn't equally obtainable via software.

That's not to say high-resolution scans aren't useful for obtaining detailed images! Scanning even a tiny photo at very high DPI will produce an image with lots of ("true") resolution. That's because the source image CONTAINS at least that level of detail already. You can scan a photo at 800dpi and get great results, because actual (darkroom-)printed photographs have a much higher resolution, potentially into the thousands of DPI. (Slides, even more so -- it's possible to have a slide with detail that's equivalent to 4000 or more DPI!) Even if the image is a digital print from a magazine or photo printer, the source DPI is in the hundreds.

Images for the screen/web, by contrast, are at "screen resolution" -- only a few hundred total pixels in each dimension, because they're meant to be displayed at roughly 96 DPI. So, Leo's 200 pixel fox could be around half an inch wide or so, when printed "actual size" on a consumer 300-600dpi photo printer. And it still won't produce a very detailed scan, no matter how high you set the resolution.

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