Troubleshooting Photos –
Enlargement Dominated By Unrealistic Visible Squares Of Color
Problem
When enlarged, the photo changed from an attractive image to a collection of colored squares as seen in pixellated.
The old excursion steamer in pixellated acquired its blocky appearance immediately on being enlarged 400% (right at the upper limit for any enlargement by normal means) from original. artifacts is a JPEG that was saved, worked on and re-saved. The easiest way of determining what action caused the disaster is to review what you did to the picture. Failing that, consider what types of area are dominated by visible pixels.
What should you look for?
There are two routes to filling a photo with ragged blocks of color like the ones you see above in pixellated. Fortunately, it's easy to tell which is the cause.
One route is to enlarge a photo using the simplest, crudest settings in your software. This simply takes each of the photo's pixels and makes it bigger, with the result you see in pixellated, big chunks of color that makes the little ship look as if it were made of Lego blocks.
Another route to blocky color is to work on and save a JPEG repeatedly. This will produce a lot of artifacts, unrealistic squares of color that you might confuse with the effects of crude enlargement, particularly if the photo also happened to have been badly enlarged (as artifacts was, as the make-artifacts-then-enlarge sequence is a common error).
Look at original – tiny as it is, you can see that it has a lot of detail in the steamer and some variation in the water, but the sky is a fairly even blue. In pixellated, you can see that all the obvious blocks of color are found in the detail areas. The sky, on the other hand, is still a fairly even blue. Since all the pixels are more or less the same color, they look the same whether they're a reasonable size as in original, or oversize as in pixellated. What has happened to the photo, then, is that all the pixels have simply been made bigger, with unpleasant results.
Since the squares in artifact have appeared out of nowhere, we can assume that they're artifacts created by mishandling the JPEG file. Mishandling of JPEGs, particularly repeated editing and saving, will produce color blocks throughout the image, and especially in areas of uniform color such as the sky.
If you have a photo like artifacts, go to this page, which deals with the artifact problem. If you have a photo like pixellated, read on.
What should you do?
Start over – a photo this badly pixellated isn't repairable, but this time, use the correct enlargement settings. Ideally start over by going back to an untouched original or a copy of the original (which you always should have – never work with a photo unless you have a duplicate). If this is your only example and if the working version is still open, select 'revert to saved version' or hit 'undo' as many times as is necessary to return to the original state. If you've saved and closed the photo, try just shrinking it back to its original dimensions, using the same routine you used to enlarge it (which was probably called something like "Nearest Neighbor" or "Enlarge Pixels" depending on what photo editing program you used).
How do you fix it?
Once you have a copy of the original (or near-original) open in front of you, resize it using the Bicubic enlargement routine in your Image Size or Resize Image dialog. This will produce smooth flows of color and while it will not give you the detail that would be present if the photo had been taken at higher pixel dimensions, it will properly render the detail that is present.
For an explanation of the best options for resizing your photos (enlarging and down-sizing photos), read the pages, About Re-sizing Photos I – How and About Re-sizing Photos II – Why.
