초록 ▼

Graphics images are generally considered to be those images comprised of text and/or line drawings. Data compression of graphics images is desired whenever a fast image transmission speed is desired in a limited band width channel. It is also used for storage of a large number of images in a limited

Graphics images are generally considered to be those images comprised of text and/or line drawings. Data compression of graphics images is desired whenever a fast image transmission speed is desired in a limited band width channel. It is also used for storage of a large number of images in a limited capacity storage system. The method and apparatus described herein improves data compression, resolution and coding efficiency by eliminating transitions between gray levels at edges in an image, converting all gray levels to a common value to achieve a 3 level representation of a graphics image, and reversibly converting the 3 level representation to a bilevel double resolution representation by increasing the data sampling rate and therefore allowing the use of two level data compression techniques. A high resolution display or printed output may be obtained from the bilevel multiresolution representation.

대표청구항 ▼

1. In a method for converting a graphics image into data representing the intensity values of the image pixels in binary format as either of two extreme values, e.g., black and white, as well as intermediate intensity values between said two extreme values, e.g., grays, to achieve efficient compress

1. In a method for converting a graphics image into data representing the intensity values of the image pixels in binary format as either of two extreme values, e.g., black and white, as well as intermediate intensity values between said two extreme values, e.g., grays, to achieve efficient compression, resolution, and coding, the improvement comprising the step of: changing the intensity value of each pixel having an intermediate intensity value within a first predetermined range of said intermediate intensity values to a predetermined one of said extreme intensity values if said pixel is adjacent to a pixel having an intermediate intensity value within a second predetermined range of said intermediate intensity values. 2. A method according to claim 1, wherein pixels within said first predetermined range of intermediate intensity values are gray-white and pixels within said second range of intermediate intensity values are gray-black, and further comprising the steps of: detecting all gray-white pixels adjacent to gray-black pixels; and changing the intensity value of each such gray-white pixel to white. 3. A method according to claim 1, comprising the further step of: changing the intensity values of all pixels having intensity values among a first plurality of intermediate intensity values to a value among a second plurality of fewer intermediate intensity values. 4. A method according to claim 1, further comprising the step of: changing the intensity value of each pixel having an intermediate intensity value to a common predetermined intermediate intensity value. 5. A method according to claim 4 wherein said changing step comprises the use of a lookup table. 6. A method according to claim 1, further comprising the steps of: converting each representation of a pixel having an intermediate intensity value to a plurality of representations of extreme intensity values in accordance with the intensity values of its adjacent pixels; and converting an original representation of each pixel having an extreme intensity value to a plurality of representations, each of said plurality of representations having an extreme intensity value corresponding to the original representation. 7. A method according to claim 6 wherein said converting step comprises the use of a lookup table. 8. A method according to claim 6, comprising the further step of: encoding each of said pixel represntations for storage of said image data. 9. A method according to claim 6, further comprising the step of: encoding each of said pixel representations for transmission of said image data. 10. A method according to claim 9, further comprising the steps of: decoding said encoded representations; detecting each pixel having an intermediate intensity value; and changing the value of each such detected pixel to a predetermined intensity value. 11. Apparatus for improving image resolution and image data compression of a graphics image that has had the intensity values of its pixels converted into data in binary format as either of two extreme values, e.g., black and white, and intermediate intensity values, e.g., grays, comprising: means for storing said image data; and means for changing the intensity value of each pixel in said image having an intermediate intensity value within a first predetermined range of said intermediate intensity values to a predetermined one of said extreme intensity values if said pixel is adjacent to a pixel having an intermediate intensity value within a second predetermined range of said intermediate intensity range. 12. Apparatus according to claim 11, further comprising: means for changing the intensity value of each pixel having an intermediate intensity value to a common predetermined intermediate intensity value. 13. Apparatus according to claim 11, wherein pixels within said first predetermined range of intermediate intensity values are gray-white and pixels within said second range of intermediate intensity values are gray-black, and further comprising: means for detecting all gray-white pixels adjacent to gray-black pixels; and means for changing the intensity value of each such gray-white pixel to white. 14. Apparatus according to claim 11, further comprising: means for converting each representation of a pixel having an intermediate intensity value to a plurality of representations of extreme intensity values in accordance with the intensity values of its adjacent pixels; and means for converting an original representation of each pixel having an extreme intensity value to a plurality of representations, each of said plurality of representations having an extreme intensity value corresponding to the original representation. 15. Apparatus according to claim 14 wherein said converting means comprises a lookup table. 16. Apparatus according to claim 11, further comprising: means for encoding each of said pixel representations for transmission of said image data. 17. Apparatus according to claim 16, further comprising: means for decoding said encoded representations; means for detecting each pixel having an intermediate intensity value; and means for changing the value of each such detected pixel to a predetermined intensity value. 18. A method for graphics image processing to improve compression and resolution comprising the steps of: converting a graphics image into data in binary format representing the intensity values of the image pixels as either of two extreme values, black and white, or of two intermediate intensity values between said two extreme values, gray-black and gray-white; detecting all gray-white pixels adjacent to gray-black pixels in the image; and changing the intensity value of each such gray-white pixel to white. 19. A method as in claim 18, comprising the further steps of: changing the intensity values of all pixels having an intermediate intensity value to a common intermediate intensity representation, gray; converting each gray representation to a pair of extreme representations each in conformance with the representation of its adjacent extreme intensity value pixel; converting each extreme value pixel representation to a pair of identical extreme value representations; and encoding all of said pixel representations for the transmissions of said image data. 20. A method as in claim 19 wherein said converting steps comprise the use of a lookup table.