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5Contrast stretchP - The Contrast Stretch • Image enhancement has become an important part of GIS • Image enhancement is map generalization

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Unformatted text preview: The Contrast Stretch • Image enhancement has become an important part of GIS • Image enhancement is map generalization with raster imagery • Image is a database:Snapshot in time • The Image Analyst decides what is important • Necessary to reduce or generalize Visual Thresholds • Humans can resolve 8-16 grey tones simultaneously • Others interpreted as patterns and textures • Image Enhancement is map generalization – Reduce information to what is needed – Enhance differences that may be slight Image Enhancement • Does not find anything that is not in the raw data, but – Using tone (grey scale) to enhance • Pattern • Texture • Shape • Context Histogram Equalization • Program tries to reasign rasters to grey scales • Attempts to put an equal amount in each grey scale, 0-255 • Does this by combining groups of grey scale values • May distort spectral characteristics • Chief advantage: Quick and easy Typical Reflectance Water, Trees, Grass, Buildings True for visible and NIR wavelengths Image Histogram (Single band)...
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This note was uploaded on 12/21/2010 for the course GIS 4037c taught by Professor Roberts during the Spring '10 term at FAU.

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5Contrast stretchP - The Contrast Stretch • Image enhancement has become an important part of GIS • Image enhancement is map generalization

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