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Setting Despeckle Parameters

Setting Despeckle Parameters
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You can instruct PPP to remove the speckles from your images. These options can be set in the Despeckle group (Figure 6-22) at the top of the Cleanup page.


Figure 6-22. Despeckle Options

You can choose from the following options:


  • No speckle removal. If this option is selected, the image processor will not clear the speckles from the input images.
  • Single speckle removal. Choose this to remove the single pixel objects from a bitonal image.
  • Remove objects between. Choose this option to remove speckles of the specified size range from a bitonal image. Be sure not to use values that are too large. The image processor might remove the dot from the letter 'i' and the periods from the end of sentences.


If your input is a bitonal image, you can exactly specify the size of the connected components. PPP will remove all the components within the specified range.


However, PPP can not do the same thing with grayscale or color images. In a color image, like a photo, you usually do not even have connected components. Though the image might have several components, their boundaries are usually fuzzy. It is very hard to define what a connected component is, because their edges are not sharp. Even if we could find the connected components in a color image, what could we do with them? Filling them with a perfectly white brush is not always the best solution, because the background might be yellow, blue, or something very complex, like clouds in the sky or objects in the background. Therefore we have a special despeckle function for grayscale and color images, which is totally different than the bitonal despeckle.


When the input image is grayscale or bitonal, PPP finds the small sharp objects and makes them smaller and smoother by changing their color. It does not matter if you choose Single speckle removal or Remove objects between, PPP will do the same thing, independently from the settings. Of course you can turn off the despeckle by selecting No speckle removal.


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