1. Field of Invention
This invention relates to modifying an appearance of an image formed by an image forming device. More particularly, this invention is directed to a method and apparatus for detecting embedded pixels of an image and altering the level of such detected embedded pixels when forming a hard copy of the image.
2. Description of Related Art
U.S. Pat. Nos. 5,666,470 to Parker and 5,687,297 to Coonan et al., each co-owned by the assignee of this application and each incorporated by reference herein in its entirety, are directed to image forming systems that allow the appearance of a printed copy of an image to be tuned. Particularly, the various definitions and image appearance tuning systems and methods set forth in the incorporated '470 and '297 patents are specifically incorporated herein.
In particular, each of these patents is directed to an image forming device that forms an image based on a bitmap, i.e., a one-bit-depth image data map, or a bytemap i.e., a multi-bit-depth image data map. The appearance tuning systems of these patents apply morphological filters to the bitmap or bytemap to determine which pixels of the bitmap or bytemap require appearance tuning. In particular, the appearance tuning systems disclosed in these patents apply predefined templates to the bitmap or bytemap and scan the templates on a pixel-by-pixel basis over the bitmap or bytemap. Each template defines a different pattern of image data values for a center pixel of interest and one or more adjacent, or "neighboring," pixels of the bitmap or bytemap. If the center pixel of interest and its neighboring pixels do not match any of the predetermined templates, the appearance of the center pixel of interest is not altered. Otherwise, depending on which of the predetermined templates is matched by the center pixel of interest and its neighboring pixels, the appearance of the center pixel of interest is altered to tune the overall appearance of the image to be formed.
In particular, the '470 patent is directed to dilation or erosion of the image data value of the pixel of interest to smooth the transition from neighboring black pixels to neighboring white pixels. In particular, dilation refers to increasing the density of the pixel of interest, i.e., making the pixel of interest darker. In contrast, erosion refers to decreasing the density of the pixel of interest, i.e., making the pixel of interest lighter. The '297 patent also modifies the image data value of the pixel of interest to increase or decrease its image data value based on the image data values of its neighboring pixels. In general, the '297 patent differs from the '470 patent primarily in the set of predetermined templates that are used in the template matching or morphological filtering operation.