When converting an image scanned in color to bitonal, it is often best to do this in stages, rather than all at once. Color images contain data that can be used to provide preliminary cleanup, which will produce a better bitonal image. An example of a process that might be useful in a color to bitonal conversion are:

1. Use ImageDetergent to clean the background color, so there will be less potential for noise in the bitonal image.
2. Use ColorDrop to drop bright colors to darker colors, so they will threshold to black, or to light colors so they will threshold to white.
3. Use VirtualBulb to drop out forms, or to drop colored paper to white.
4. Use AdjustBrightnessContrast to make sure all images have bright whites and dark blacks.

Once the image is converted to a more suitable form, then Binarize or AutoBinarize should be used to complete the conversion to bitonal.

Examples

The following section shows examples of images from steps 1-4 above.

Example of Image Detergent:

Example of Color Drop:

Example of Virtual Bulb:

Example of Adjust Brightness Contrast:

Example of Autobinarize: