Method and apparatus for rotation of high addressability bitmap images
AssigneeXerox Corporation
InventorMartin E. Banton
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Abstract
The present invention is a method and apparatus for consistently rotating high addressability bitmap images to be rendered on a printing system. The invention first encodes the high addressability image to produce a regular bitmap array and then rotates the regular array. Next the invention applies a compact dot growth operation to assure that the exposure pulses for any gray pixels are consistently positioned, thereby assuring consistent output-independent of the rotation direction.
Claims16
A printing system for rotating a high addressability binary bitmap received for printing, the bitmap including an anamorphic two-dimensional array of input image signals, where a first resolution along a first dimension exceeds a second resolution along a second dimension, the printing system comprising:
- an encoder for encoding the input image signals to produce a bitmap image that is represented by a regular two-dimensional array of multi-bit image signals having a resolution in both dimensions that is equivalent to the second resolution;
- a first memory for storing the array of multi-bit image signals at the second resolution;
- a rotation circuit for rotating the multi-bit image signals stored in said first memory with respect to the orientation of the input image so as to produce a rotated image at the second resolution;
- a second memory for storing the image signals of the rotated image;
- a compact dot growth circuit, operating on the multi-bit image signals stored in said second memory, for generating output signals, each output signal generated in response to a gray multi-bit image signal having an exposure pulse positioned in response to the states of the multi-bit signal and adjacent multi-bit image signals;
- and
- an output engine for outputting an image representation in response to the high addressability signals generated by said compact dot growth circuit.
A method, operating in a printing system for rotating a high addressability binary bitmap received for printing by the system, the bitmap including an anamorphic two-dimensional array of input image signals, where a first resolution along a dimension exceeds a second resolution along a second dimension, the method comprising the steps of:
- encoding the input image signals to produce a bitmap image that is represented by a regular two-dimensional array of multi-bit image signals having a resolution in both dimensions that is equivalent to the second resolution;
- storing the array of multi-bit image signals in a first memory at the second resolution;
- rotating the multi-bit image signals stored in the first memory in an increment of about 90.degree. with respect to the orientation of the input image so as to produce a rotated image at the second resolution;
- storing the image signals of the rotated image in a second memory;
- in response to the multi-bit image signals stored in the second memory, generating high addressability binary signals, wherein each high addressability signal generated in response to a multi-bit image signal has an exposure pulse positioned in response to the states of the multi-bit signal and adjacent multi-bit image signals;
- and
- outputting an image representation in response to the the high addressability signals generated by said compact dot growth circuit.
A method, operating on a programmable computer, for rotating a binary input bitmap image in about 90.degree. increments, said input bitmap image representing binary image signals at an N.times.M resolution, where N=P.times.M and where P is an integer that is greater than 1, said method comprising the steps of:
- encoding the N.times.M resolution image bitmap to produce a second, P-bit per pixel image bitmap at an M.times.M resolution;
- rotating the second bitmap;
- operating on the M.times.M rotated bitmap to identify those P-bit per pixel signals representing gray pixels therein and producing a third binary image bitmap, wherein exposure pulses for the third binary image bitmap are selectively repositioned within a pixel exposure period so that the pulses abut a pulse from an adjacent pixel period causing the resultant dot for the adjacent pixel period to enlarge upon development.
Dependencies are inferred from the claim text.