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Image processing method, apparatus, and storage medium for recognition or irradiation areaRelated Patent Categories: Image Analysis, Applications, Dna Or Rna Pattern Reading, X-ray Film Analysis (e.g., Radiography)Image processing method, apparatus, and storage medium for recognition or irradiation area description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060002602, Image processing method, apparatus, and storage medium for recognition or irradiation area. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an image processing method, an image processing apparatus, and a storage medium using secondary differences for recognition of an irradiation field. [0003] 2. Related Background Art [0004] The recent progress in the digital technology makes it common to convert a radiographic image to a digital image signal, subject this digital image signal to image processing, and display it on a CRT or the like or print it out. In photography of the radiographic image it is common practice to diaphragm the irradiation area so as to radiate the radiation only into a necessary area of a human body on the humane grounds or for the reason of preventing scattering from unnecessary areas so as to prevent lowering of contrast. Normally, a processing parameter is determined from distribution of density values of the image prior to the image processing and the image processing is then carried out based on the parameter thus determined. However, if the irradiation area is not limited, unwanted information, in a sense, outside an area of interest is used for the determination of the image processing parameter, which poses a problem that appropriate image processing is not effected. [0005] It is thus necessary to extract the irradiation area and determine the image processing parameter from information of only the area of interest. As an extraction method of the irradiation area, for example, Japanese Patent Application (Laid-Open) No. 05-007579 describes a method for dividing the image area into small areas and extracting the irradiation area, based on values of variance in the small areas. Further, for example, Japanese Patent Publication No. 6-90412 describes a method for expressing a change of image densities between a predetermined number of pixels near an end portion of the image area by an approximate equation substantially of a linear equation and extracting the irradiation area, based on the difference between assumed image density values according to this approximate equation and actual density values indicated by a sample image signal. [0006] These methods are predicated on the premise that an object area in the photographic image includes the irradiation area (an area actually irradiated), and a process of judging whether the object area is an area including the irradiation area (which will also be referred to as an "area with an irradiation diaphragm") or an area not including the irradiation area (which will also referred to as an "area without the irradiation diaphragm") is carried out as a preliminary operation before execution of these methods. [0007] Methods for judging presence/absence of the irradiation diaphragm include methods for comparing an average, a median, or the like of densities in a central area of the image with an average of densities of the object area and judging that the object area is an area with the irradiation diaphragm, if the average of densities of the object area is not more than a predetermined value, as described in U.S. Pat. No. 5,091,970, for example. SUMMARY OF THE INVENTION [0008] The method of above Japanese Patent Application (Laid-Open) No. 05-007579 had to obtain the density variance in each small area and thus had the problem of increased computation complexity and computation time. Even within the area of interest, density values vary suddenly, for example, at the edge of the lang field and a change rate of densities could become higher there than at the edge of the irradiation area. Particularly, the variances become high in the area where the lang is in contact with the ribs at the edge of the lang. This caused candidate points for the irradiation area to be extracted from outside the edge of the irradiation area as well and this posed another problem that the judgment became difficult. [0009] In the method of above Japanese Patent Publication No. 6-90412, a foot area outside the irradiation area was assumed for calculation of the linear approximate equation and there arose the problem that the method was invalid if this foot area was not able to be extracted well. Further, it was also assumed that the foot area outside the irradiation area included two areas of a gentle portion and a quickly rising portion and this posed another problem that the method was invalid where the entire foot area was gentle or where there were three or more changes of density gradient. [0010] The present invention has been accomplished in order to solve the problems described above and an object of the invention is, therefore, to extract the irradiation area accurately. [0011] An image processing method of the present invention is an image processing method comprising: [0012] a step of determining a plurality of areas arranged in a predetermined direction on an image and each having a predetermined shape; [0013] a step of calculating a secondary difference value of density values representing the respective areas in the plurality of areas; and [0014] a step of judging one end point of an irradiation area from the secondary difference values calculated in the calculating step. [0015] In the conventional image judgment method as described in above U.S. Pat. No. 5,091,970 etc., for example, where the photographic image is one in a state in which the subject overlaps with the edge of the image, the average density value at the end of the image varies depending upon the area of the subject over the edge of the image and upon the transmittance of the radiation. Therefore, the presence/absence of the irradiation diaphragm was sometimes misjudged in the area at the end of the image. [0016] When the radiant dose of the irradiation diaphragm was small, the density difference also became small between the central part of the image and the object area and the presence/absence of the irradiation diaphragm in the object area was misjudged in some cases. [0017] The present invention has been accomplished to eliminate the drawbacks described above and an object of the invention is, therefore, to make it possible to accurately judge whether an image area as a processed object is an area including the irradiation area. [0018] An image processing method of the present invention is an image processing method for extracting an irradiation area in an input image, the image processing method comprising: [0019] a step of detecting an irradiation end, based on a density distribution in each area, for a plurality of areas in a desired direction in the image; and [0020] a step of evaluating the result of the detection, based on the result of irradiation ends detected for each of the plurality of areas. [0021] Another image processing method of the present invention is an image processing method for judging whether an object area in an image includes an irradiation area, the method comprising: [0022] a secondary difference value acquisition step of acquiring secondary difference values from one-dimensional image data of the object area; Continue reading about Image processing method, apparatus, and storage medium for recognition or irradiation area... 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