Dehalftoning of digital images
First Claim
1. A method blending graphics objects comprising:
- receiving a first graphics object;
rendering the first graphics object to produce a first pixel map having a first bit depth;
providing a second pixel map associated with a second graphics object that is to be blended with the first graphics object, the second pixel map having a second bit depth, where the second bit depth is less than the first bit depth;
increasing the second bit depth of the second pixel map; and
blending the first and second pixel maps.
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Accused Products
Abstract
Methods and apparatus for blending graphics objects. In one aspect, a method includes receiving a first graphics object; rendering the first graphics object to produce a first pixel map having a first bit depth; increasing a bit depth of a second pixel map associated with a second graphics object that is to be blended with the first graphics object, where the second bit depth is less than the first bit depth; and blending the first and second pixel maps. The method may be implemented to blend graphics objects received by a printing device. In one embodiment, the invention features blending deep pixel data received by a printing device with corresponding shallow halftoned data stored in a shallow frame buffer. The invention may be implemented as a printer configured to receive a page description language description of a page to be printed, the printer including a dehalftone engine for deriving deep pixel data values for objects stored in a shallow frame buffer. In another aspect, the invention features using a pixelmap representative of underlying graphics data for transfer between a host and a remote device by transmitting a halftone representation of the pixelmap from the host to the remote device and reconstructing the pixelmap at the remote device from the halftone representation and a threshold matrix.
78 Citations
31 Claims
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1. A method blending graphics objects comprising:
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receiving a first graphics object; rendering the first graphics object to produce a first pixel map having a first bit depth; providing a second pixel map associated with a second graphics object that is to be blended with the first graphics object, the second pixel map having a second bit depth, where the second bit depth is less than the first bit depth; increasing the second bit depth of the second pixel map; and blending the first and second pixel maps. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method blending graphics objects received by a printing device comprising:
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rendering a first graphics object to produce a first pixel map having a first bit depth; restoring a bit depth of a second pixel map associated with a second graphics object that is to be blended with the first graphics object to the first bit depth, where the second pixel map was previously rendered at a second bit depth that was less than the first bit depth; and blending the first and second pixel maps.
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16. A method blending graphics objects received by a printing device comprising:
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receiving a first graphics object; rendering the first graphics object to produce a first pixel map having a first bit depth; reducing the bit depth of the first pixel map; storing the first pixel map; receiving a second graphics object to be blended with the first graphics object; rendering the second graphics object to produce a second pixel map, the second pixel map including data at a blend bit depth; increasing the bit depth of the first pixel map to the blend bit depth; blending the first and second pixel maps.
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17. A method blending deep pixel data received by a printing device with corresponding shallow data stored in a shallow frame buffer, the method comprising:
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receiving deep pixel data associated with a first graphics object; restoring deep pixel data values from shallow pixel data stored in the shallow frame buffer associated with a second graphics object previously rendered into the shallow frame buffer; and blending the deep pixel data associated with the first graphics object and restored deep pixel data associated with the second graphics object.
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18. A printer configured to receive a page description language description of a page to be printed, comprising:
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a render engine for rendering received page description objects for the page into deep pixel data; a halftone engine operating on deep pixel data to create halftone data representative of the objects; a shallow frame buffer for storing halftone data; a dehalftone engine for approximating deep pixel data values for objects stored in the shallow frame buffer resulting in restored deep pixel data; a blending engine for blending rendered deep pixel data and restored deep pixel data resulting in blended data, the blended data operated on by the halftone engine to derive halftone data for storage in the shallow frame buffer; and a print engine for printing halftone data from the shallow frame buffer resulting in a blending of image data according to a user defined blending function.
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19. A method of deriving deep pixel data from halftone data comprising:
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computing a dehalftone region size; dividing the halftone data into regions according to the dehalftone region size; checking each region for flatness, and further sub-dividing each region that is not flat until each resulting sub-region is flat; and for each region and sub-region calculating a singular deep pixel data value representative of a shade in that region. - View Dependent Claims (20)
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21. A method of transmitting graphics data between a host and a remote device comprising:
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transmitting a halftone representation of a pixelmap from the host to the remote device; reconstructing the pixelmap at the remote device from the halftone representation and a threshold matrix used to construct the halftone representation. - View Dependent Claims (22, 23, 24, 25, 26)
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27. A method of transmitting a pixelmap representative of underlying graphics data for transfer between a host and a remote device, the pixelmap having a first bit depth, the method comprising:
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reducing the bit depth of the pixelmap; transmitting a reduced bit depth representation of the pixelmap from the host to the remote device; and reconstructing the pixelmap at the remote device. - View Dependent Claims (28, 29, 30)
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31. A method of increasing the bit depth of a reduced bit depth pixelmap of the form of halftone data representative of an underlying image, comprising:
generating a pixelmap from the halftone data and a threshold matrix used to construct the halftone data by grouping regions of halftone data according to shading and adjacency and calculating a single shade for all regions within a group.
Specification