Method and apparatus for compressing and decompressing images of documents
First Claim
Patent Images
1. An image compression system for compressing an input image from an image source comprising:
- a binary image generator to generate a binary image representing an estimate of the bi-level information in the input image, wherein the binary image includes edge information in the input image;
a post binary image generator coupled to the binary image generator to filter the binary image to produce a processed binary image;
a subtractor coupled to the post binary image generator to subtract the processed binary image from the input image to produce a difference image, wherein the processed binary image is subtracted from the input image on a pixel-by-pixel basis;
a post subtraction processing mechanism coupled to the subtractor to reduce components in the difference image created by mismatching between binary edges in the processed binary image and the input image to produce a resulting image, wherein portions of edges produced in the difference image due to fractional pixel misalignment between the processed binary image and the input image are removed from the processed binary image to create the resulting image;
a binary compressor coupled to the binary image generator to receive the binary image and compress the binary image into compressed binary data; and
continuous-tone compressor coupled to the post subtraction processing mechanism to compress the resulting image into compressed continuous-tone data, such that the input image is compressed into compressed binary data and compressed continuous-tone data.
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Abstract
A method and apparatus for compressing images having a binary extractor, a binary compressor and a JPEG compressor. The binary extractor produces a binary image representing an estimate of the binary information in the original image. The binary image is compressed by the binary compressor. The binary image is also subtracted from the original image to produce a difference image representing the continuous-tone information in the original image. The difference image is then compressed using the JPEG compressor. In this manner, the present invention compresses a document image without having to perform segmentation on the image.
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Citations
33 Claims
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1. An image compression system for compressing an input image from an image source comprising:
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a binary image generator to generate a binary image representing an estimate of the bi-level information in the input image, wherein the binary image includes edge information in the input image; a post binary image generator coupled to the binary image generator to filter the binary image to produce a processed binary image; a subtractor coupled to the post binary image generator to subtract the processed binary image from the input image to produce a difference image, wherein the processed binary image is subtracted from the input image on a pixel-by-pixel basis; a post subtraction processing mechanism coupled to the subtractor to reduce components in the difference image created by mismatching between binary edges in the processed binary image and the input image to produce a resulting image, wherein portions of edges produced in the difference image due to fractional pixel misalignment between the processed binary image and the input image are removed from the processed binary image to create the resulting image; a binary compressor coupled to the binary image generator to receive the binary image and compress the binary image into compressed binary data; and continuous-tone compressor coupled to the post subtraction processing mechanism to compress the resulting image into compressed continuous-tone data, such that the input image is compressed into compressed binary data and compressed continuous-tone data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A compression system for compressing an input image comprising:
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a binary image generator to generate a binary image representing an estimate of the bi-level information in the input image, wherein the binary image includes edge information in the input image; a point spread modeling mechanism coupled to the binary image generator to receive the binary image and smooth the binary image to create a smoothed binary image; a binary compressor coupled to the binary image generator to compress the binary image into compressed binary data; a differencing mechanism coupled to receive the input image and the smoothed binary image to create a difference image, wherein the differencing mechanism includes a subtractor to subtract the smoothed binary image from the input image on a pixel-by-pixel basis; a masking mechanism coupled to the differencing mechanism to reduce error in the difference image due to any fractional pixel misalignment of edges between the input image and the smoothed binary image to produce a masked image, wherein portions of edges produced in the difference image created by mismatching between binary edges in the input image and the smoothed binary image are removed to create the masked image; and a continuous-tone compressor coupled to the masked image to compress the masked image into compressed continuous-tone data, such that the input image is compressed into compressed binary data and compressed continuous-tone data. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A compression system for compressing an input image comprising:
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a binary image generator for generating a binary image representing an estimate of the bi-level information in the input image, wherein the binary image includes edge information in the input image; a point spread model coupled to the binary image generator for receiving the binary image and smoothing the binary image to create a smoothed binary image; a binary compressor coupled to the binary image generator for compressing the binary image into compressed binary data; a subtracter coupled to receive the input image and the smoothed binary image to create a difference image on a pixel-by-pixel basis; visual masking filter coupled to the subtracter for reducing error in the difference image due to any fractional pixel misalignment of edges between the input image and the smoothed binary image; and continuous-tone compressor coupled to the visual making filter for compressing the masked image, such that mosquito noise is reduced when the input image is reconstructed.
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23. A decompression system for decompressing image data that included compressed binary image data and compressed continuous-tone image data into a reconstructed version of the original image, said system comprising:
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a binary decompressor to decompress the compressed binary image data to produce a binary image; a modeling mechanism coupled to the binary decompressor to receive the binary image and process the binary image to create a processed binary image; a continuous-tone image decompressor to decompress the compressed continuous-tone image data to produce a continuous-tone image; and a combining mechanism to combine the processed binary image and the continuous-tone image on a pixel-by-pixel basis to produce the reconstructed version of the original image. - View Dependent Claims (24, 25, 26)
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27. A decompression system for decompressing image data corresponding to an original image, wherein the image data includes compressed binary image data and compressed continuous-tone image data, and wherein the image data is decompressed into a reconstructed version of the original image, said system comprising:
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a binary decompressor coupled to receive the compressed binary image data for decompressing the compressed binary image data to produce a binary image having a first plurality of pixels; a point spread filter coupled to receive the binary image for performing an area convolution on the binary image using an approximation of the point spread function of the source of the original image to create a smoothed binary image; a continuous-tone image decompressor coupled to receive the continuous-tone image data wherein the continuous-tone decompressor decompresses the compressed continuous-tone image data to produce a continuous-tone image having a second plurality of pixels; and an adder coupled to receive the smoothed binary image and the continuous-tone image for combining the smoothed binary image and the continuous-tone image on a pixel-by-pixel basis to produce the reconstructed version of the original image.
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28. A reproduction system for reproducing an image source comprising:
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scanning means for scanning the image source into image data; compression means coupled to the scanning means for compressing the image data, wherein the compression means includes binary image generation means for generating a binary image representing an estimate of the bi-level information in the input image, wherein the binary image includes edge information in the input image; post binary image generation processing means coupled to the binary image generation means for filtering the binary image to produce a smoothed binary image; subtraction means coupled to the post binary image generation processing means for subtracting the processed binary image from the input image to produce a difference image wherein the processed binary image is subtracted from the input image on a pixel-by-pixel basis; post subtraction processing means coupled to the subtraction means for reducing components in the difference image created by mismatching between binary edges in the processed binary image and the input image to produce a resulting image., wherein portions of edges produced in the difference image due to fractional pixel misalignment between the processed binary image and the input image are removed from the processed binary image to create the resulting image; binary compression means coupled to the binary image generation means for receiving the binary image and compressing the binary image into compressed binary data; and continuous-tone compression means coupled to the post subtraction processing means for compressing the resulting image into compressed continuous-tone data, such that the input image is compressed into compressed binary data and compressed continuous-tone data, decompression means coupled to the binary compression means and continuous-tone compression means for decompressing the compressed binary image data and the compressed continuous-tone image data into reconstructed image data; display means for producing a visual display of the image data. - View Dependent Claims (29)
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30. A document archiving system for use with a document image comprising:
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input means for producing image data representing the document image; compression means coupled to the input means for compressing the image data, wherein the compression means includes binary image generation means for generating a binary image representing an estimate of the bi-level information in the input image, wherein the binary image includes edge information in the input image, post binary image generation processing means coupled to the binary image generation means for filtering the binary image to produce a smoothed binary image, subtraction means coupled to the post binary image generation processing means for subtracting the smoothed binary image from the input image to produce a difference image wherein the smoothed binary image is subtracted from the input image on a pixel-by-pixel basis; post subtraction processing means coupled to the subtraction means for reducing high frequency components in the difference image created by mismatching between binary edges in the smoothed binary image and the input image to produce a resulting image, wherein portions of edges produced in the difference image due to fractional pixel misalignment between the smoothed binary image and the input image am removed from the processed binary image to create the resulting image; binary compression means coupled to the binary image generation means for receiving the binary image and compressing the binary image into compressed binary image data into compressed binary data; and continuous-tone compression means coupled to the post subtraction processing means for compressing the resulting image into compressed continuous-tone image data; and storage means for storing the document image as compressed binary image data and compressed continuous-tone image data. - View Dependent Claims (31)
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32. A facsimile system for transferring a document image comprising:
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scanning means for inputting the document image as image data; transmission means for transmitting the image data, wherein the transmission means includes compression means coupled to the scanning means for compressing the image data and channel means for sending the image data, wherein the compression means includes binary image generation means for generating a binary image representing an estimate of the bi-level information in the input image, wherein the binary image includes edge information in the input image, post binary image generation processing means coupled to the binary image generation means for filtering the binary image to produce a smoothed binary image, subtraction means coupled to the post binary image generation processing means for subtracting the smoothed binary image from the input image to produce a difference image, wherein the smoothed binary image is subtracted from the input image on a pixel-by-pixel basis; post subtraction processing means coupled to the subtraction means for reducing high frequency components in the difference image created by mismatching between binary edges in the smoothed binary image and the input image to produce a resulting image, wherein portions of edges produced in the difference image due to fractional pixel misalignment between the smoothed binary image and the input image are removed from the processed binary image to create the resulting image; binary compression means coupled to the binary image generation means for receiving the binary image and compressing the binary image into compressed binary image data into compressed binary data; and continuous-tone compression means coupled to the post subtraction processing means for compressing the resulting image into compressed continuous-tone image data, such that the channel means sends the compressed binary image data and compressed continuous-tone image data. - View Dependent Claims (33)
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Specification