Method and apparatus for compressing mixed text and image data
First Claim
1. A method of compressing data of mixed types having different priority levels to within a given size, comprising the steps of:
- separating said data of mixed types into data of a first type and data of a second type, the data of said first type having a higher priority than the data of said second type;
compressing the data of said first type using a first compression method, producing compressed data of said first type;
storing the compressed data of said first type in a memory area having said given size;
calculating a remaining size of said memory area by subtracting a size of the compressed data of said first type from said given size;
selecting a second compression method having a compression ratio not less than a ratio of a size of the data of said second type to said remaining size;
compressing the data of said second type using said second compression method, producing compressed data of said second type; and
storing the compressed data of said second type in said memory area.
1 Assignment
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Accused Products
Abstract
To convert a mixture of text data and dot-mapped image data to compressed dot-mapped data not exceeding a given size, the text data are converted to dot-mapped data, then losslessly compressed, after which the dot-mapped image data are down-sampled as necessary. To compress dot-mapped data to within a given size, lossless compression, lossy compression, and down-sampling followed by compression are attempted until the necessary size reduction is achieved. To convert a page of object data to compressed dot-mapped data, the objects are classified and prioritized, then rasterized and compressed by different methods according to their priorities. The compression ratios are predicted and monitored, and the compression parameters are modified according to the prediction error.
147 Citations
39 Claims
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1. A method of compressing data of mixed types having different priority levels to within a given size, comprising the steps of:
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separating said data of mixed types into data of a first type and data of a second type, the data of said first type having a higher priority than the data of said second type; compressing the data of said first type using a first compression method, producing compressed data of said first type; storing the compressed data of said first type in a memory area having said given size; calculating a remaining size of said memory area by subtracting a size of the compressed data of said first type from said given size; selecting a second compression method having a compression ratio not less than a ratio of a size of the data of said second type to said remaining size; compressing the data of said second type using said second compression method, producing compressed data of said second type; and storing the compressed data of said second type in said memory area. - View Dependent Claims (2, 3, 4, 5, 32, 33, 34)
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6. An apparatus for compressing data of mixed types having different priority levels to within a given size, comprising:
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a data separator for separating said data of mixed types into data of a first type and data of a second type, the data of said first type having a higher priority than the data of said second type; a first data compressor for compressing the data of said first type using a first compression method, producing compressed data of said first type; a control unit coupled to said first data compressor, for calculating a remaining size by subtracting a size of the compressed data of said first type from said given size, then calculating a compression ratio by comparing a size of the data of said second type with said remaining size; and a second data compressor for compressing the data of said second type according to said compression ratio, producing compressed data of said second type. - View Dependent Claims (7, 8, 9, 35, 36, 37)
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10. A method of compressing dot-mapped data to within a given size, comprising the steps of:
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compressing said dot-mapped data using a first compression method, thereby producing first compressed data according to a first compression ratio; comparing a size of said first compressed data with said given size; compressing said dot-mapped data using a second compression method having a second compression ratio which is greater than said first compression ratio, thereby producing second compressed data, if the size of said first compressed data exceeds said given size; comparing a size of said second compressed data with said given size; and compressing said dot-mapped data using a third compression method having a third compression ratio which is greater than said second compression ratio, said third compression method including at least a reduction of resolution, thereby producing third compressed data, if the size of said second compressed data exceeds said given size. - View Dependent Claims (11, 12, 13)
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14. An apparatus for compressing dot-mapped data to within a given size, for transmission of the compressed data from a computing device to a peripheral device, comprising:
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first compression means, disposed in said computing device, for compressing said dot-mapped data to produce first compressed data according to a first compression ratio; second compression means, disposed in said computing device, for compressing said dot-mapped data to produce second compressed data according to a second compression ratio which is greater than the first compression ratio; resolution-reducing means, disposed in said computing device, for reducing a resolution of said dot-mapped data by a specifiable ratio; and a control unit coupled to said first compression means and said second compression means, for selecting said first compressed data if said first compressed data have a size not exceeding said given size, for selecting said second compressed data if said first compressed data have a size exceeding said given size and said second compressed data have a size not exceeding said given size, and for directing said resolution-reducing means to reduce said dot-mapped data, then selecting one compression means from between said first compression means and said second compression means and directing the selected compression means to compress the dot-mapped data as reduced by said resolution-reducing means, if both said first compressed data and said second compressed data have sizes exceeding said given size. - View Dependent Claims (15, 16, 17)
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18. A method of compressing data describing a group of objects forming a page of a documents to within a given size for transmission from a computing device to a peripheral device, comprising the steps of:
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dividing said data into object data describing individual objects of different types on said page; classifying said objects according to object type; assigning priorities to said objects, according to object type; selecting compression parameters for each of said objects, to said priorities; and compressing the object data according to corresponding compression parameters, thereby producing compressed data. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 38)
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26. An apparatus for compressing object data describing a group of objects forming a page of a document to within a given size for transmission from a computing device to a peripheral device, comprising:
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an object classifier, for reading header information about said objects, including information about object type, and classifying said objects according to object type; a prioritizer coupled to said object classifier, for assigning priorities to said objects, responsive to object type; a compression parameter selector coupled to said prioritizer, for selecting compression parameters for each of said objects, according to said priorities; and a data compressor coupled to said compression parameter selector, for compressing said object data using different methods having different compression ratios, according to the compression parameters selected by said compression parameter selector, thereby producing compressed data. - View Dependent Claims (27, 28, 29, 30, 31, 39)
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Specification