Details:
Summary:
Given a particular algorithm, such as error diffusion, the print produced by it may be enhanced by consideration of the printing system. This is especially true for ink-jet printing. The quality of a print is very strongly dependent upon the combination of ink and paper used. A useful first step is to print a series of grey levels. (Note: For error diffusion, any grey level may be simulated depending upon the area to be covered. For an ordered dither algorithm, these levels are quantized.) These levels may be measured instrumentally and converted to a form which correlates well with visual perception. From these measurements an adjustment is made that equal differences in grey level are also perceived as being nearly equal. The grey levels will also show obvious artifacts due to the algorithm. In the case of error diffusion, this usually is seen as a texture such as a Herring Bone pattern. It is possible to remove these artifacts in error diffusion by randomizing the threshold. The grey levels will also show obvious artifacts due to the algorithm. In the case of error diffusion, this usually is seen as a texture such as a Herring Bone pattern. It is possible to remove these artifacts in error diffusion by randomizing the threshold. Once these adjustments have been made the algorithm should be checked to make sure it is not adding noticeable frequency patterns. A sine wave variation or a Fresnel zone plate may be used for this. The final on the algorithm should be several pictures. These should be rated visually by a reasonably large number of observers.