Image Enhancement via Adaptive Unsharp MaskingWhat is Unsharp Masking?ObjectiveSolutionAlgorithmAlgorithm cont…SchematicResultsResults cont…Measuring Quality of EnhancementConclusionImage Enhancement via Adaptive Unsharp MaskingBy Isha JhaWhat is Unsharp Masking?Want to emphasize high frequency contents of an image.Z(n,m) is a high pass filtered version of image controls the level of contrast enhancementDisadvantages: Noise in smooth regions Overshoot artifactsObjectiveIncreasing dynamics in smooth areas amplifies noise – so no emphasisHigh contrast areas already have high local dynamics – Require low enhancement to avoid overshootMedium contrast areas require most enhancementSolutionUse Adaptive Unsharp Masking- varies according to predefined rules0 -1 0-1 4 -10 -1 -1ZAlgorithmMeasure of Local Dynamics g(.)Algorithm cont… – positive convergence parameter – step sizeSchematicResultsResults cont…Measuring Quality of EnhancementDesired Behavior given bye(n,m)=gd(n,m)-gy(n,m)Look at e2 Cost FunctionConclusionThe adaptive approach prevents highlighting of noise in smooth areasIn areas with high contrast it produces medium enhancement to avoid artifactsHighest enhancement in regions with medium
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