Advanced Despeckle pane
You can use advanced despeckle preprocessing to remove blobs on an image. This image cleanup method has the following options:
- Mass (pixels)
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Set the range of the minimum and maximum number of black pixels for an unwanted blob. By default, the value for the maximum number is set to 50 pixels to remove common noise and stray marks caused by scanning. Use this option to remove blobs that are too small or large to be actual characters. For large blobs you only have to estimate the appropriate number of connected pixels for the minimum mass.
Note You should consider the resolution of the document when estimating the number of pixels. For example, a faxed document. When either the minimum or maximum value is set to 0, the mass is ignored. This means that the pixel value has no effect on blob calculation. - Proportion (%)
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Set the minimum and maximum proportion of dark pixels for a blob. The number of connected dark pixels is divided by the total number of pixels in the smallest rectangle that contains the entire blob. Use this option to remove blobs that are unlikely to be a real character. A typical proportion for real characters is around 40%, depending on the font, so the value for the maximum proportion needs to be lower than this. However, if you want to remove larger blobs, you can use a minimum proportion of around 60%. When either the minimum or maximum value is set to 0, this value has no effect on the blob calculation.
- Width (pixels)
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Set the value for the minimum and maximum width by specifying the number of horizontal pixels of an unwanted blob.
- Height (pixels)
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Set the value for the minimum and maximum height by specifying the number of vertical pixels of an unwanted blob.
- Separation (pixels)
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Set the value for the minimum separation to define the minimum distance of a blob to any other dark pixel in the image. Blobs with a larger mass can typically be removed safely if they are distant from other marks.
- Include diagonal connections
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Select this option so that diagonally adjacent pixels are connected to form one blob. If cleared, a one pixel thick diagonal line is treated as separate single-pixel speckles. This option is cleared by default.