Manual:$wgSharpenReductionThreshold

ImageMagick: $wgSharpenReductionThreshold
Reduction in linear dimensions below which sharpening will be enabled.
Introduced in version:1.10.0 (r21411)
Removed in version:Still in use
Allowed values:(decimal between 0 and 1)
Default value:0.85

Details

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See $wgSharpenParameter for an explanation of this parameter.