Abstract: A method for optimizing rendering of objects to be printed on a white background, includes identifying an object of a particular type to be printed on a white background, wherein objects of the particular type have predefined rendering hints associated with them, which predefined rendering hints provide optimized rendering of the objects of the particular type on non-white backgrounds; associating a new tag called “object on white” with the identified object; defining a new rendering hint for rendering the object of the particular type on a white background with the identified object; and rendering objects with the object on white tag according to the new rendering hint.

Abstract: Methods and apparatus for antialiasing images that contain one or more image objects such as colored text, line art, and graphical objects, such that the edge pixels of an antialiased image object will exhibit relatively uniform values, and the appearance of the image object is thereby improved. In one embodiment, an improved antialiasing filter is employed to detect at least one region within the received image. Upon detecting a region containing a background image level that adjoins an image object having pixel values in a range other than a range of limit values, the antialiasing filter sets the pixel values of the edge or border pixels of the image object to substantially the same value. Selection among a logical filter operation and an averaging filter operation may be adaptively employed in the antialiasing filter in order to obtain the desired uniformity of pixel values.

Abstract: A method for smooth trapping of an object containing run length encoded image pixel data, includes collecting a number of scanlines of run length encoded pixel data equal to 2M in a buffer, wherein M is a line width trap threshold; determining those runs within the collected scanlines that require trapping, wherein a run is a portion of a scanline; if trapping is required in the fast scan direction and the length of the run requiring trapping is less than M, reducing the width of the trap region by a prorated percent. If trapping is required in the slow scan direction, and the number of runs above and below the run to be trapped is less than M, reducing the number of runs above and below the run to be trapped by a prorated percentage.

Abstract: A method for selecting which rendering hint or tag to use when multiple tags may be associated with a pixel, includes prioritizing the set of input tags associated with an input image, such that each input tag has a unique priority relative to other input tags in the set; filtering the input image by selecting groups of input pixels, applying a filtering function to the contone data associated with each selected group of input pixels, and producing an output pixel having an output contone data for each selected group of input pixels; for each selected group of input pixels, comparing the priorities of the input tags associated with the selected group of input pixels and selecting as the output tag associated with the output pixel, that tag with the highest priority.

Abstract: A method for smooth trapping of thin graphical objects, wherein a thin graphical object has a width dimension which is substantially less than the object's length dimension, includes receiving from a trap generator the location of a trap pixel that should be changed in color; determining the width of the object containing the trap pixel; comparing the width of the object with a trap threshold width; if the size of the object is less than the trap threshold width, reducing the width of the trap region according to a predetermined relationship; and applying a trap correction to the trap pixel according to the reduced trap width. The predetermined relationship may be a linear relationship which reduces the trap width monotonically for object widths less than the trap threshold width. The method may be applied to small objects and small font text objects.

Abstract: A method of correction for toner misregistration in color printing systems, specifically for run length encoded image data. This method, called “trapping”, usually involves extending the color separations one or more pixels to overlay the edge. The color of the “trap zone” is chosen such that it is nearly imperceptible in the presence of the two initial colors. Our approach assumes the existence of a “trap generator”, which provides a trap color given two input colors. In run length encoded image format, the image is comprised of an array of “scanlines”, consisting of a string of “runs” that are specified by a minimum position in the fast (horizontal) direction, a length, and a color. We describe a method of trapping involving the following steps: 1) inspecting the run lengths in each scanline to determine the color edges of the image; 2) sending the colors at the boundaries to the trap generator to determine the trap color; and 3) modifying the intersecting runs with the trap color.

Abstract: A method for selecting which rendering hint or tag to use when multiple tags may be associated with a pixel, includes prioritizing the set of input tags associated with an input image, such that each input tag has a unique priority relative to other input tags in the set; filtering the input image by selecting groups of input pixels, applying a filtering function to the contone data associated with each selected group of input pixels, and producing an output pixel having an output contone data for each selected group of input pixels; for each selected group of input pixels, comparing the priorities of the input tags associated with the selected group of input pixels and selecting as the output tag associated with the output pixel, that tag with the highest priority.

Abstract: A method of improving edge rendering of objects includes dilation (or contraction) of an object's tag plane by one or more pixels into the surrounding region, with the adjacent tag region having a corresponding contraction (or dilation). The objects of interest (e.g., white text) are first identified; the corresponding object tag plane is then spread or choked, in a fashion analogous to trapping. In the case of negative text on a tint background, by expanding the tag plane for the negative text object, the text hint would be forced one pixel into the tint object plane everywhere along the perimeter of the negative text. This could then enable greatly improved negative text rendering.

Abstract: A method for optimizing rendering of objects to be printed on a white background, includes identifying an object of a particular type to be printed on a white background, wherein objects of the particular type have predefined rendering hints associated with them, which predefined rendering hints provide optimized rendering of the objects of the particular type on non-white backgrounds; associating a new tag called “object on white” with the identified object; defining a new rendering hint for rendering the object of the particular type on a white background with the identified object; and rendering objects with the object on white tag according to the new rendering hint.

Abstract: A method of improving edge rendering of objects containing run length encoded image pixel data collects two run-length encoded scanlines (upper and lower). Each run transition is inspected for the presence of interesting runs (object tag planes to be grown or shrunk). Depending on the position of the interesting runs relative to the run transition (e.g., in upper or lower scanline, to right or left of boundary), the tag planes of the surrounding runs will be modified. If a tag plane needs to be modified in the fast scan direction, a new run (one or more pixels in length, with the original color) is inserted at the run transition and assigned to the tag plane of the interesting run. If a tag plane needs to be modified in the slow scan direction, the run is subdivided and subsequently assigned to the tag plane of the interesting run.

Abstract: Methods and apparatus for antialiasing images that contain one or more image objects such as colored text, line art, and graphical objects, such that the edge pixels of an antialiased image object will exhibit relatively uniform values, and the appearance of the image object is thereby improved. In one embodiment, an improved antialiasing filter is employed to detect at least one region within the received image. Upon detecting a region containing a background image level that adjoins an image object having pixel values in a range other than a range of limit values, the antialiasing filter sets the pixel values of the edge or border pixels of the image object to substantially the same value. Selection among a logical filter operation and an averaging filter operation may be adaptively employed in the antialiasing filter in order to obtain the desired uniformity of pixel values.

Abstract: A method for smooth trapping of thin graphical objects, wherein a thin graphical object has a width dimension which is substantially less than the object's length dimension, includes receiving from a trap generator the location of a trap pixel that should be changed in color; determining the width of the object containing the trap pixel; comparing the width of the object with a trap threshold width; if the size of the object is less than the trap threshold width, reducing the width of the trap region according to a predetermined relationship; and applying a trap correction to the trap pixel according to the reduced trap width. The predetermined relationship may be a linear relationship which reduces the trap width monotonically for object widths less than the trap threshold width. The method may be applied to small objects and small font text objects.

Abstract: A method for smooth trapping of an object containing run length encoded image pixel data, includes collecting a number of scanlines of run length encoded pixel data equal to 2M in a buffer, wherein M is a line width trap threshold; determining those runs within the collected scanlines that require trapping, wherein a run is a portion of a scanline; if trapping is required in the fast scan direction and the length of the run requiring trapping is less than M, reducing the width of the trap region by a prorated percent. If trapping is required in the slow scan direction, and the number of runs above and below the run to be trapped is less than M, reducing the number of runs above and below the run to be trapped by a prorated percentage.

Abstract: A method for correcting a white line artifact between low and high frequency printed pixels. A printer may be able to print either a high or low frequency halftone pixels in some locations, but may be able to print only high frequency halftone pixels in other locations, the latter known as out of phase locations. If the image data is in run length encoded form, and the printer tries to print a low frequency pixel in an out of phase location, no pixel will be printed in that location and a white space results. The remedy is to test at the beginning and end of low frequency runs bordering high frequency runs. If the first (last) low frequency pixel of an original run is in an out of phase location, a one pixel run of the high frequency screen and of the low frequency color is added before (after) the original run, and the run length of the low frequency run is decreased by one pixel.

Abstract: Trapping is a method well known in the graphical arts industry, and provides a remedy for color misregistration defects on printed images. The general technique of trapping involves the placement of a small patches of colored pixels at the edges of colored objects, such that the color associated with these patches appears neutral to the human eye relative to the original colors present. The technique of trapping, however, assumes the objects being trapped are much larger in dimension than the trap zone itself. For small objects, a visible hue shift relative to the original color may occur as a result of the trapping operation. For run length encoded data, the remedy for this is a method that determines the object size by inspecting the run length of a run to be trapped in the fast scan direction, and counting the number of runs above or below that run with an identical color.

Abstract: A method for correcting for edge defects caused by print characteristics of a print engine includes printing a set of actual color patches corresponding to a desired set of colors; defining an edge region and a uniform area region in each of the patches; for each color patch in the set of actual color patches: determining a difference between color in the edge region of the patch and color in the uniform area region of the patch; and generating an edge response to adjust color output of the print engine in the edge region to substantially match color output in the uniform area region. The method can perform edge correction for any edge region of an image. In one embodiment of the invention, the edge region may be determined by a trap engine associated with the print engine and the method can provide correction for trap pixels.

Abstract: A method of correction for toner misregistration in color printing systems, specifically for run length encoded image data. This method, called “trapping”, usually involves extending the color separations one or more pixels to overlay the edge. The color of the “trap zone” is chosen such that it is nearly imperceptible in the presence of the two initial colors. Our approach assumes the existence of a “trap generator”, which provides a trap color given two input colors.

Abstract: Thin film spatial filters are disclosed. The filters are constructed with a continuous thin film of low resistance conductor (for example with a resistance of from 10−2 to 108 Ohms-cm) with plurabilty of resistive elements defining pixels. A thin film of high resistance material is on other side of the pixels in the case of grounded filters. The conductor film provides lateral blurring for image processing.