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JPEG File Repair

(October 2002) posted on Wed Oct 09, 2002

Tired of spending hours trying to clean up low-quality JPEG files so that they're suitable for separating and printing?

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By Mark A. Coudray

JPEG compression breaks an image into rectangular blocks, each representing 8 x 8 pixels of detail, and then independently compresses each block. The result of JPEG compression on a file that was of poor original quality is an ugly, repetitive pattern of blocks. Such over-compression can take place when an image is saved as a JPEG file in computer software like Photoshop, or when an image is captured at a low resolution with hardware like a scanner or digital camera.


A solution in sight


With JPEG files so commonplace, how can we ever see our way past these obstacles? Well, hope is on the horizon. Alien Skin Software LLC has released Image Doctor, a beta-version plug-in filter for bitmap-editing software. According to the developer, this set of powerful image-retouching tools for Photoshop, Fireworks, Paint Shop Pro, Corel Photopaint, and other image editors, magically removes blemishes and defects, quickly repairs over-compressed JPEGs, and seamlessly replaces unwanted details and objects.


When one of my customers tipped me off about this product, I immediately went to the company's Website (which is listed at the end of this column) and downloaded the filters. One of the key components I discovered in the software is JPEG Repair. JPEG Repair reduces the damage caused by over-compressing JPEG image files, making the images more aesthetically pleasing <B>(Figures 1A and 1B)</B>.


Working with Image Doctor is very easy, and the results you get are impressive. Not only will it work on overcompressed JPEGs, but it also provides excellent overall image repair on files that have been polluted with dust and dirt during scanning or scanned from scratched photos and slides.


The amount of retouching you apply to an image is completely up to you. Upon opening an image in Image Doctor, the program presents you with a retouching screen that contains slider bars for applying selective blurring and grain additions. The following procedures are all it takes to use the program's JPEG Repair feature:


1. Select the image area to be repaired.


2. Starting from the lowest setting, incrementally move the Remove Artifacts slider until the blocky defects of JPEG compression are no longer visible. But be careful not to exceed the slider position at which they seem to diminish.



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