# US 5,710,840 A · Image processing method and apparatus for adjusting the tone density of pixels based upon differences between the tone density of a center pixel and tone densities of peripheral pixels > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,840 A - Document ID: US5710840A - Status: Granted - Kind: A - Application number: 08/468,226 - Filed: 1995-06-06 - Granted: 1998-01-20 - Earliest claimed: 1993-04-26 - Assignees: Fuji Photo Film Co., Ltd. - Inventors: Takahiro Hideshima; Ushio Anayama - Web page: https://patentgrep.com/patent/US5710840A ## CPC - G06T 5/20: using local operators - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL ## Abstract An image processing method and apparatus capable of sufficiently emphasizing binary density image area without deterioration of the image quality of a gray-scale or middle tone image area. During image processing, a density A.sub.0 of a center pixel is converted into a density ›A!.sub.0 by the formula; ›A!.sub.0 =A.sub.0 +K.sub.1 .times.(.vertline..SIGMA.(A.sub.0 -A.sub.i).vertline.-K.sub.2).times..SIGMA.(A.sub.0 -A.sub.i) wherein A.sub.i is a density of peripheral pixels surrounding the center pixel and K.sub.1 and K.sub.2 are constants, respectively. ## Claims ### Claim 1 A computer-implemented image processing method for emphasizing an image, including a middle tone density area and a binary density area consisting of black and white picture elements, comprising the steps of: sensing said image with a sensor to form a plurality of pixels, each of said pixels having a tone density; designating a center pixel and a plurality of peripheral pixels; determining a sum of differences between the tone density A.sub.0 of said center pixel and the tone density A.sub.i of each of said peripheral pixels; adjusting the tone density A.sub.0 of said center pixel based upon a quadratic function of said sum to produce an adjusted tone density A.sub.0 ', such that said image is edge-sharpened in said binary density area without deterioration of the image quality of said image in said middle tone density area; and outputting the adjusted tone density signal. ### Claim 2 (depends on 1) The image processing method according to claim 1, wherein the adjusted tone density A.sub.0 ' is produced according to the following equation: A.sub.0 '=A.sub.0 +K.sub.1 .times.(.vertline..SIGMA.(A.sub.0 -A.sub.i).vertline.-K.sub.2).times..SIGMA.(A.sub.0 -A.sub.i) where K.sub.1 and K.sub.2 are constants. ### Claim 3 (depends on 2) The image processing method according to claim 2, wherein K.sub.1 =1/256 and K.sub.2 =16. ### Claim 4 (depends on 1) The image processing method according to claim 1, wherein said peripheral pixels comprise eight pixels which are directly adjacent to said center pixel. ### Claim 5 (depends on 2) The image processing method according to claim 2, wherein said peripheral pixels comprise eight pixels which are directly adjacent to said center pixel. ### Claim 6 (depends on 3) The image processing method according to claim 3, wherein said peripheral pixels comprise eight pixels which are directly adjacent to said center pixel. ### Claim 7 (depends on 1) The image processing method according to claim 1, wherein said peripheral pixels comprise eight pixels which are no further than one pixel in distance away from said center pixel in main and subsidiary scanning directions. ### Claim 8 (depends on 2) The image processing method according to claim 2, wherein said peripheral pixels comprise eight pixels which are no further than one pixel in distance away from said center pixel in main and subsidiary scanning directions. ### Claim 9 (depends on 3) The image processing method according to claim 3, wherein said peripheral pixels comprise eight pixels which are no further than one pixel in distance away from said center pixel in main and subsidiary scanning directions. ### Claim 10 (depends on 1) The image processing method according to claim 1, wherein said pixels are stored as digital density signals which represent the tone densities of said pixels by multinarized tone graduation. ### Claim 11 (depends on 1) The image processing method according to claim 1, wherein said peripheral pixels are non-adjacent to said center pixel. ### Claim 12 An apparatus for emphasizing an image including a middle tone density area and a binary density area consisting of black and whim picture elements, comprising: an image sensor for sensing the image and forming image data consisting of a plurality of pixels each having a tone density; storing means for storing said pixels; and processing means for designating a center pixel and a plurality of peripheral pixels, for determining a sum of differences between the tone density A.sub.0 of said center pixel and the tone density A.sub.i of each of said peripheral pixels, and for adjusting the tone density A.sub.0 of said center pixel based upon a quadratic function of said sum to produce an adjusted tone density A.sub.0 ', such that said processing means edge-sharpens said image in said binary density area without deterioration of the image quality in said middle tone density area. ### Claim 13 (depends on 12) The apparatus according to claim 12, wherein the adjusted tone density A.sub.0 ' is produced according to the following equation: A.sub.0 '=A.sub.0 +K.sub.1 .times.(.vertline..SIGMA.(A.sub.0 -A.sub.i).vertline.-K.sub.2).times..SIGMA.(A.sub.0 -A.sub.i) where K.sub.1 and K.sub.2 are constants. ### Claim 14 (depends on 13) The apparatus according to claim 13, wherein K.sub.1 =1/256 and K.sub.2 =16. ### Claim 15 (depends on 12) The apparatus according to claim 12, wherein said peripheral pixels comprise eight pixels which are directly adjacent to said center pixel. ### Claim 16 (depends on 13) The apparatus according to claim 13, wherein said peripheral pixels comprise eight pixels which are directly adjacent to said center pixel. ### Claim 17 (depends on 14) The apparatus according to claim 14, wherein said peripheral pixels comprise eight pixels which are directly adjacent to said center pixel. ### Claim 18 (depends on 12) The apparatus according to claim 12, wherein said peripheral pixels comprise eight pixels which are no further than one pixel in distance away from said center pixel in main and subsidiary scanning directions. ### Claim 19 (depends on 13) The apparatus according to claim 13, wherein said peripheral pixels comprise eight pixels which are no further than one pixel in distance away from said center pixel in main and subsidiary scanning directions. ### Claim 20 (depends on 14) The apparatus according to claim 14, wherein said peripheral pixels comprise eight pixels which are no further than one pixel in distance away from said center pixel in main and subsidiary scanning directions. ### Claim 21 (depends on 12) The apparatus according to claim 12, wherein said storage means stores said pixels as digital density signals which represent the tone densities of said pixels by multinarized tone graduation. ### Claim 22 (depends on 12) The apparatus according to claim 12, wherein said peripheral pixels are non-adjacent to said center pixel.