A filter is a special kind of tool designed to take an input layer or image, apply a mathematical algorithm to it, and return the input layer or image in a modified format. GIMP uses filters to achieve a variety of effects and those effects are discussed here.
        
          The filters are divided into several categories:
          
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                Section 3, “Blur Filters”
               
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                Section 4, “Enhance Filters”
               
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                Section 5, “Distort Filters”
               
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                Section 6, “Light and Shadow Filters”
               
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                Section 7, “Noise Filters”
               
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                Section 8, “Edge-Detect Filters”
               
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                Section 9, “Generic Filters”
               
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                Section 10, “Combine Filters”
               
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                Section 11, “Artistic Filters”
               
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                Section 12, “Decor Filters”
               
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                Section 13, “Map Filters”
               
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                Section 14, “Rendering Filters”
               
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                Section 15, “Web Filters”
               
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                Section 16, “Animation Filters”