Image despeckling relates to bi-tonal images. These may be imported as bi-tonal or may be generated, explicitly or implicitly, from grayscale or color images. Image despeckling can improve the quality of auto-zoning, recognition, and the automatic pre-processing transformations: the detection of inverted characters, skew, and orientation is more reliable when run on a despeckled bi-tonal image.

The function IG_REC_image_despeckle() immediately despeckles a single bi-tonal image in the recognition engine's memory space. This functions independently of the despeckle mode setting and the resolution of the original image. The transformed image replaces the original one, keeping its format, and is available to the application.

An image despeckling mode setting is given by IG_REC_despeckle_mode_set(), with Boolean values TRUE and FALSE (default: TRUE ). This mode setting influences bi-tonal images with a resolution of 280 dpi or greater. This mode setting is applied whenever any of the following functions are called:

• IG_REC_zones_locate()
• IG_REC_image_recognize()
• IG_REC_image_preprocess() with IG_REC_IMG_DESKEW_AUTO, IG_REC_IMG_ROTATE_AUTO, or IG_REC_IMG_INVERT_AUTO

When a grayscale or color image is converted to bi-tonal, it usually results in a cleaned image. This can be influenced by the values in IG_REC_secondary_reduction_mode_set() and IG_REC_reduction_threshold_set().

With these mode-induced transformations, the cleaned or despeckled bi-tonal image exists in parallel with the original one and is not available to the application.