Optipix User's Guide:  JPEG Cleaner

JPEG Cleaner is simple, effective method for reducing the characteristic 'block' artefacts that the JPEG compression process leaves in your images. Many 'point-and-shoot' cameras do not have a RAW or TIFF output setting, but any intensive processing of these images, such as the Optipix Refocus or Interactive Interpolation tools, can exacerbate the JPEG effect to the point of visual undesirability.

Running JPEG Cleaner as a first step before processing will usually reduce these artefacts to the point where further processing is possible. If the JPEG quality is low, then it may be necessary to run JPEG Cleaner twice to adequately remove the artefacts.

If the image does not contain significant block artefacts from JPEG compression, the plug-in will not modify it and will report this fact.

The plug-in works by automatically locating the 8x8 pixel block boundaries in the image, and then processing the pixel values adjacent to those boundaries to make the abrupt steps less visible. For users who wish to use their own processing routines on those edges, the "Select JPEG Tile Boundaries" plugin under the selection menu can be used to locate the edges, and place a selection around them that can be used to limit the application of whatever algorithm is then employed.

The images above show a portion of a JPEG image compressed with medium quality before (top) and after (bottom) JPEG Cleaner. The blocky artefacts have been reduced to the point that further processing with Interactive Interpolation would not exacerbate the damage. The user could run JPEG Cleaner again if they felt that the damage was not sufficiently repaired, or use our JPEG selection plug-in to touch up the tile boundaries manually.

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