Resolution enhancement may be performed internally during image conversions. It involves a doubling of the resolution of a bi-tonal image resulting from an implicit secondary image conversion from grayscale or color. The doubling is performed on the basis of information available from the greater pixel depth in grayscale and color images. The resulting bi-tonal image exists in parallel with the original one, and is not available to the application.

The application has no control over when resolution doubling is done, only on whether and how it is done. The function IG_REC_res_enhancement_mode_set() accepts one of five settings from enumIGRecImgResEnhancement:

• IG_REC_IMG_RE_NO: No resolution enhancement applied.
• IG_REC_IMG_RE_YES: Apply enhancement, ratio = 2.0.
• IG_REC_IMG_RE_LEGACY: The ratio of the enhancement depends on the resolution of the non-BW image. The ratio is 2.0 if the resolution is less than or equal to 150 DPI, and it is 1.5 if the resolution is less than or equal to 200 DPI. Otherwise resolution enhancement is not applied.
• IG_REC_IMG_RE_STANDARD: The ratio is detected dynamically: it depends on the resolution of the non-BW image and on the detected average character size.
• IG_REC_IMG_RE_AUTO: Enhancement depends on the current tradeoff setting: if tradeoff is IG_REC_TO_FAST use IG_REC_IMG_RE_LEGACY, otherwise use IG_REC_IMG_RE_STANDARD. IG_REC_IMG_RE_AUTO is the default setting.