Patent ID: 9716811
Date: 2017-07-25
CPC Classifications: H04N

Claim:
1. A method for obtaining a cross-section of a color gamut of an image forming apparatus by slicing the color gamut along a plane and making a determination therefrom, the method comprising: obtaining gamut boundary line segments that are baseline segments of a boundary of the color gamut of the image forming apparatus; obtaining endpoints for cross-section boundary line segments, the obtained endpoints being points of intersection of the obtained gamut boundary line segments and the plane; obtaining the cross-section boundary line segments that are baseline segments for a boundary of the cross-section of the color gamut of the image forming apparatus, the obtained cross-section boundary line segments being line segments defining a route that is a shortest route passing through all of the obtained endpoints only once; displaying a cross-section boundary with the obtained cross-section boundary line segments; and determining whether a specified chromaticity value is inside or outside the cross-section of the color gamut of the image forming apparatus using the obtained cross-section boundary line segments, wherein obtaining the gamut boundary line segments further comprises: obtaining endpoints of line segments in a Lab color space by converting the endpoints of the line segments in a RGB color space into points in the Lab color space; and obtaining the gamut boundary line segments in the Lab color space, based on obtained endpoints in the Lab color space, by a formula 1, {Li,ai,bi} denoting a point on a line segment, {Ls,as,bs} denoting a start point, which is one of the two endpoints of a line segment, {Le,ae,be} denoting an ending point, which is the other point of the line segment, and “t” is a parameter from 0 to 1; and wherein obtaining the endpoints for the cross-section boundary line segments further comprises: obtaining a formula 2, in one of the cases where, (i) a user has already specified a plane including a specified point X {Lx,ax,bx} and having a constant lightness, or (ii) it has been already determined to obtain the cross-section boundary line segments taken by slicing a color gamut of the image forming apparatus along a plane having a lightness Lx, the plane is represented by the formula 2; obtaining a formula 4, in the case where the user has already specified a plane including the specified point X {Lx,ax,bx} and having a constant hue, the plane is represented by a formula 3, and is specified by three points: a black point K {0,0,0} present on an L axis; a white point W {100,0,0} present on the L axis; and the specified point X {Lx,ax,bx}, then the formula 3 is represented as the formula 4; obtaining a formula 5, in one of the cases where (i) the user has already specified a plane having a specified hue angle Hd, or (ii) it has been already determined to obtain the cross-section boundary line segments taken by slicing the color gamut of the image forming apparatus along a plane having the hue angle Hd, the plane is represented by the formula 5; and obtaining a formula 6, in the case where the user has already specified a plane including the specified point X {Lx,ax,bx} and having a normal vector {p,q,r}, the plane is represented by the formula 6,