Black and white images use dithering, often called dot shading, to simulate shades of gray. This feature removes areas of dot shading from an image, including actual black-on-white shading. This option allows OCR reading of dot shaded text by automatically detecting zones of shading, determining the size of individual dots, and then removing them. The Dot Shading Removal feature handles a wide range of dot sizes.
Another benefit of removing dot shading is that it can improve the compression of an image file, since the compression algorithm no longer has to store as much information. Additional compression of 50% or more is possible.
Option |
Description |
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Density Adjustment |
Sets a value used to adjust the expected density of dot shading areas. Range -50-50 Values from -5 to +5 cover nearly all typical cases. Note:
Negative numbers instruct the tool to search for shaded areas with more white pixels than black pixels. Positive numbers instruct the tool to search for shaded areas with more black pixels than white ones. |
Max Dot Size |
Determines the maximum size of individual dots that make up the dot shading. Dots up to and including this size will be removed. Range 0-20 |
Min. Area Height |
Sets the height of the smallest dot-shaded area to process. You can decrease this value in order to detect shorter dot shaded zones, or increase it to reduce false detects or if all dot shaded areas are taller than the default size. Range 0-20,000 |
Min. Area Width |
Sets the width of the smallest shaded zone to process. You can decrease this value in order to detect thinner dot shaded zones. Increase this value in order to reduce false detects or when all the shaded areas are wide. Range 0-20,000 |
Horizontal Size Adjustment |
Modifies the horizontal component of the dot shading removal feature. This causes the dot removal feature to remove dots one pixel wider than the size specified in Maximum dot size. Set to 2 to remove dots which are two pixels wider. Set to -1 or -2 if text is being degraded (leaving horizontal white streaks). This decreases the width of the dots being sought by one or two pixels, and spares small text. Range -100-100 |
Vertical Size Adjustment |
Modifies the vertical component of the dot shading removal feature. This causes the dot removal feature to remove dots one pixel taller than the size specified in Maximum dot size. Set to -1 or -2 if text is being degraded (leaving vertical white streaks). Range -100-100 |