Image signal encoding apparatus

• US 6,118,552 A
• Filed: 08/06/1996
• Issued: 09/12/2000
• Est. Priority Date: 09/21/1993
• Status: Expired due to Fees

• Current Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Original Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Inventors: Umezawa, Ken, Yoshinari, Toshiaki, Suzuki, Kazuhiro, Yokose, Taro
• Primary Examiner(s): Lee, Thomas D.
• Application Number:
  US08/693,382
• Time in Patent Office: 1,498 Days
• Field of Search: 358/426, 358/429, 358/432, 358/433, 358/443, 358/448, 358/462, 358/464, 358/465, 358/467, 358/530, 358/539, 382/232, 382/239, 382/243, 382/162, 382/166
• US Class Current: 382/166
• CPC Class Codes: H04N 1/642 Adapting to different types of images, e.g. characters, graphs, black and white image portions

Abstract

An image signal encoding apparatus reads an image from an original and converts the image into color data values including lightness and chromaticity components. The data values are stored and divided into pixel blocks with data values of lightness components and pixel blocks with data values of chromaticity components. Average lightness component data values are computed for pixel blocks of lightness components and average chromaticity data values are computed for pixel blocks of chromaticity components. A region determination is made whether the pixel blocks correspond to color, monochrome or background region in the original based on the average pixel block data values of lightness components and chromaticity components. A switch outputs the lightness pixel block data values during the region determination, and outputs the lightness and chromaticity pixel block data values after the region determination. The lightness pixel block data values are adaptively bi-level connected based on the result of the region determination. A bi-level image encoder encodes lightness pixel block data values converted by adaptive bi-level conversion and the result of the region determination is stored as region information. A color image encoder encodes the chromaticity pixel block data values consisting of man pixels determined to correspond to the color region based on the stored region information after the region determination process on the whole original is completed and a transmitter transmits at least one of the set of data values encoded by the bi-level image encoder and the set of data values encoded by the color image encoder.

Claims

1. An image signal encoding apparatus, comprising:

image inputting means for reading an image from an original and converting said image into data values comprising a plurality of color components including lightness and chromaticity components and outputting said data values;

storing means for storing each of said data values;

dividing means for dividing said data values into data values of a rectangular pixel block of lightness component consisting of m×

n pixels and data values of rectangular pixel blocks of chromaticity components consisting of m×

n pixels, where m and n are positive integers;

image analysis means for generating an average data value separation block by calculating an average lightness component data value of m×

n pixels in said pixel block of lightness component and average chromaticity component data values of m×

n pixels in said pixel blocks of chromaticity components and obtaining the difference between said average lightness component data value and said average chromaticity component data values for performing waveform analysis in said pixel blocks based on a plurality of statistics of said average data value separation block including variance, histogram values and maximum and minimum values and for outputting waveform information and said average data values of m×

n pixels of said pixel blocks of lightness component and chromaticity components;

region determination means for determining whether said rectangular pixel block correspond to a color, monochrome, or background region in the original based on said average data values of m×

n pixels of said pixel blocks of lightness component and chromaticity components and outputting a result of region determination;

switching means for outputting said data values of said pixel block of lightness component during the region determination process by said region determination means, and for outputting said data values of said pixel blocks of lightness component and chromaticity components after the region determination process is completed;

bi-level converting means for performing adaptive bi-level conversion of said data values of said pixel block of lightness component based on the result of said region determination and said waveform information;

bi-level image encoding means for encoding data values of said pixel block of lightness component converted by adaptive bi-level conversion;

region storing means for storing the result of said region determination as region information;

color image encoding means for encoding said data values of the rectangular pixel blocks of chromaticity components consisting of m×

n pixels determined to correspond to the color region by said region determination means based on said region information stored in said region storing means after said region determination process on the whole original is completed; and

transmission control means for transmitting at least one of said data values encoded by said bi-level image encoding means and said data values encoded by said color image encoding means.

2. The image signal encoding apparatus according to claim 1, wherein

said plurality of color components including said lightness and chromaticity components are selected from a group comprising:

L*a*b* and L*u*v*.

3. The image signal encoding apparatus according to claim 1, wherein

said region determination means determines that said pixel block corresponds to the background region when both of the difference between said average data value of said pixel block of lightness component and a predetermined background signal value of the original and the difference between said average data values of said pixel blocks of chromaticity components and said predetermined background signal value are not more than a predetermined threshold level, determines that said pixel block corresponds to the monochrome region when the differences between the average data values of said pixel blocks of chromaticity components and said predetermined background signal value are not more than said predetermined threshold level and the difference between the average data value of said pixel block of lightness component and said predetermined background signal value is more than said predetermined threshold level, and determines that said pixel block corresponds to the color region in all other cases.

4. The image signal encoding apparatus according to claim 1, wherein

said region determination means includes means for calculating projection profile of said pixel block determined to correspond to the color region in the original to determine a position of the color region in the original.

5. An image signal encoding apparatus, comprising:

image inputting means for reading an image from an original and converting said image into data values comprising a plurality of color components including lightness and chromaticity components and outputting said data values;

internal encoding means for dividing said data values into data values of a pixel block of lightness component and data values of pixel blocks of chromaticity components, and for each of said pixel blocks of lightness component and chromaticity components, determining an encoding mode based on waveform characteristics of said pixel block, calculating an average data value of said pixel block, and converting encoding mode information indicating said determined encoding mode, said average data value of said pixel block and waveform approximation information indicating said waveform characteristics of said pixel block to internally encoded data of a fixed length;

storing means for storing said internally encoded data for each of said pixel blocks of lightness component and chromaticity component;

separation means for separating said average data value of said pixel block and said encoding mode information from said internally encoded data for each of said pixel blocks of lightness component and chromaticity components;

internal decoding means for decoding said internally encoded data for each of said pixel blocks of lightness component and chromaticity components stored in said storing means;

region determination means for determining whether said pixel blocks correspond to a color, monochrome or background region in the original based on said average data values of said pixel blocks of lightness component and chromaticity components, and outputting a result of region determination;

switching means for outputting said data values of said pixel block of lightness component during the region determination process by said region determination means, and for outputting said data values of said pixel blocks of lightness component and chromaticity components corresponding to each determined region after the region determination process is completed;

bi-level converting means for performing adaptive bi-level conversion of said data values of said pixel block of lightness component based on the result of said region determination and said encoding mode information;

bi-level image encoding means for encoding data values of said pixel block of lightness component converted by adaptive bi-level conversion;

region storing means for storing the result of said region determination as region information;

color image encoding means for encoding said data values of the pixel blocks of chromaticity components determined to correspond to the color region by said region determination means based on said region information stored in said region storing means after said region determination process on the whole original is completed; and

transmission control means for transmitting at least one of said data values encoded by said bi-level image encoding means and said data values encoded by said color image encoding means.

6. The image signal encoding apparatus according to claim 5, wherein

said plurality of color components including said lightness and chromaticity components are selected from a group comprising:

L*a*b* and L*u*v*.

7. The image signal encoding apparatus according to claim 5, wherein

said region determination means determines that said pixel block corresponds to the background region when both of the difference between said average data value of said pixel block of lightness component and a predetermined background signal value of the original and the difference between said average data values of said pixel blocks of chromaticity components and said predetermined background signal value are not more than a predetermined threshold level, determines that said pixel block corresponds to the monochrome region when the differences between the average data values of said pixel blocks of chromaticity components and said predetermined background signal value are not more than said predetermined threshold level and the difference between said average data value of said pixel block of lightness component and said predetermined background signal value is more than said predetermined threshold level, and determines that said pixel block corresponds to the color region in all other cases.

8. The image signal encoding apparatus according to claim 5, wherein

said region determination means includes means for calculating projection profile of said pixel block determined to correspond to the color region in the original to determine a position of the color region in the original.

9. An image signal encoding apparatus, comprising:

image inputting means for reading an image from an original and converting said image into data values comprising a plurality of color components including luminance and chrominance components and outputting said data values;

storing means for storing each of said data values;

dividing means for dividing said data values into data values of a rectangular pixel block of luminance component consisting of m×

n pixels and data values of rectangular pixel blocks of chrominance components consisting of m×

n pixels, where m and n are positive integers;

image analysis means for generating an average data value separation block by calculating an average luminance component data value of m×

n pixels in said pixel block of luminance component and average chrominance component data values of m×

n pixels in said pixel blocks of chrominance components and obtaining the difference between said average luminance component data value and said average chrominance component data values for performing waveform analysis in said pixel blocks based on a plurality of statistics of said average data value separation block including variance, histogram values and maximum and minimum values and or outputting waveform information and said average data values of m×

n pixels of said pixel blocks of luminance component and chrominance components;

region determination means for determining whether said rectangular pixel blocks correspond to a color, monochrome, or background region in the original based on said average data values of m×

n pixels of said pixel blocks of luminance component and chrominance components and outputting a result of said region determination;

switching means for outputting said data values of said pixel block of luminance component during the region determination process by said region determination means, and for outputting said data values of said pixel blocks of luminance component and chrominance components after the region determination process is completed;

bi-level converting means for performing adaptive bi-level conversion of said data values of said pixel block of luminance component based on the result of said region determination and said waveform information;

bi-level image encoding means for encoding data values of said pixel block of luminance component converted by adaptive bi-level conversion;

region storing means for storing the result of said region determination as region information;

color image encoding means for encoding said data values of the rectangular pixel blocks of chrominance components consisting of m×

n pixels determined to correspond to the color region by said region determination means based on said region information stored in said region storing means after said region determination process on the whole original is completed; and

transmission control means for transmitting at least one of said data values encoded by said bi-level image encoding means and said data values encoded by said color image encoding means.

10. The image signal encoding apparatus according to claim 9, wherein

said plurality of color components including said luminance and chrominance components are selected from a group comprising:

YCbCr and YIQ.

11. The image signal encoding apparatus according to claim 9, wherein

said region determination means determines that said pixel block corresponds to the background region when both of the difference between said average data value of said pixel block of luminance component and a predetermined background signal value of the original and the differences between said average data values of said pixel blocks of chrominance components and said predetermined background signal value are not more than a predetermined threshold level, determines that said pixel block corresponds to the monochrome region when the differences between said average data values of said pixel blocks of chrominance components and said predetermined background signal value are not more than said predetermined threshold level and the difference between the average data value of said pixel block of luminance component and said predetermined background signal value is more than said predetermined threshold level, and determines that said pixel block corresponds to the color region in all other cases.

12. The image signal encoding apparatus according to claim 9, wherein

said region determination means includes means for calculating projection profile of said pixel block determined to correspond to the color region in the original to determine a position of the color region in the original.

13. An image signal encoding apparatus, comprising:

image inputting means for reading an image from an original and converting said image into data values comprising a plurality of color components including luminance and chrominance components and outputting said data values;

internal encoding means for dividing said data values of a pixel block into data values of a pixel block of luminance component and data values of pixel blocks of chrominance components, and for each of said pixel blocks of luminance component and chrominance components, determining an encoding mode based on waveform characteristics of said pixel block, calculating an average data value of said pixel block, and converting encoding mode information indicating said determined encoding mode, said average data value of said pixel block and waveform approximation information indicating said waveform characteristics of said pixel block to internally encoded data of a fixed length;

storing means for storing said internally encoded data for each of said pixel blocks of luminance component and chrominance components;

separation means for separating said average data value of said pixel block and said encoding mode information from said internally encoded data for each of said pixel blocks of luminance component and chrominance components;

internal decoding means for decoding said internally encoded data for each of said pixel blocks of luminance component and chrominance components stored in said storing means;

region determination means for determining whether said pixel blocks correspond to a color, monochrome or background region in the original based on said average data values of said pixel blocks of luminance component and chrominance components, outputting a result of region determination;

switching means for outputting said data values of said pixel block of luminance component during the region determination process by said region determination means, and for outputting said data values of said pixel blocks of luminance component and chrominance components corresponding to each determined region after the region determination process is completed;

bi-level converting means for performing adaptive bi-level conversion of said data values of said pixel block of luminance component based on the result of said region determination and said encoding mode information;

bi-level image encoding means for encoding data values of said pixel block of luminance component converted by adaptive bi-level conversion;

region storing means for storing the result of said region determination as region information;

color image encoding means for encoding said data values of the pixel blocks of chrominance components determined to correspond to the color region by said region determination means based on said region information stored in said region storing means after said region determination process on the whole original is completed; and

transmission control means for transmitting at least one of said data values encoded by said bi-level image encoding means and data values encoded by said color image encoding means.

14. The image signal encoding apparatus according to claim 13, wherein

said plurality of color components including said luminance and chrominance components are selected from a group comprising:

YCbCr and YIQ.

15. The image signal encoding apparatus according to claim 13, wherein

said region determination means determines that said pixel block corresponds to the background region when both of the difference between said average data value of said pixel block of luminance component and a predetermined background signal value of the original and the differences between said average data values of said pixel blocks of chrominance components and said predetermined background signal value are not more than a predetermined threshold level, determines that said pixel block corresponds to the monochrome region when the differences between the average data values of said pixel blocks of chrominance components and said predetermined background signal value are not more than said predetermined threshold level and the difference between the average data value of said pixel block of luminance component and said predetermined background signal value is more than said predetermined threshold level, and determines that said pixel block corresponds to the color region in all other cases.

16. The image signal encoding apparatus according to claim 13, wherein

said region determination means includes means for calculating projection profile of said pixel block determined to correspond to the color region in the original to determine a position of the color region in the original.