JP4066103B2 - Graphic clipping device and graphic clipping method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a graphic clipping device and a graphic clipping method used in, for example, an image processing device, a drawing device, a graphic editing device, and the like, and more specifically, a graphic clipping device that extracts overlapping portions of a plurality of convex polygons and The present invention relates to a figure clipping method.
[0002]
[Prior art]
  For example, in the field of computer graphics and the like, when creating or editing an image, an image processing device, a drawing device, a graphic editing device, or the like is used. These devices perform arithmetic processing on graphic data corresponding to a plurality of graphics constituting an image, and perform graphic editing processing such as deformation, movement, and deletion of the graphic.
[0003]
  Incidentally, as one of such graphic editing processes, there is a graphic clipping process. The figure clipping process is a process of cutting out (clipping) overlapping portions of a plurality of figures. A slab method is used for the graphic clipping process. The slab method is a generally known method and is described in, for example, Tetsuo Asano “Computational Geometry”, Asakura Shoten, and the like.
[0004]
  Here, a method of cutting out overlapping portions of two convex polygons will be described with reference to FIG.
[0005]
  In FIG. 11, the convex polygon P and the convex polygon Q arranged on the XY coordinate plane overlap each other. Here, the overlapping portion is defined as an overlapping portion R. Of the vertices of the convex polygon P, the top vertex is the upper end point Pu, the lowermost vertex is the lower end point Pb, and each side of the convex polygon P is the lower end point from the upper end point Pu. Each vertex that passes when tracing counterclockwise toward Pb is designated as PLi (i = 1, 2, 3,...) In the order of passage, and each side of the convex polygon P is located above the lower end point Pb. Each vertex passing when tracing counterclockwise toward the end point Pu is defined as PRj (j = 1, 2, 3,...) In the passing order. Similarly, among the vertices of the convex polygon Q, the top vertex is the upper end point Qu, the lowermost vertex is the lower end point Qb, and each side of the convex polygon Q is the lower end point from the upper end point Qu. Each vertex passing through when tracing counterclockwise toward the point Qb is defined as QLm (m = 1, 2, 3,...) In the order of passing, and each side of the convex polygon Q is defined from the lower end point Qb. Each vertex passing through when tracing counterclockwise toward the upper end point Qu is set to QRn (n = 1, 2, 3,...) In the order of passing. Furthermore, the upper left end of the figure is the origin of the XY coordinate plane, and for example, the Y coordinate of the upper end point Pu of the convex polygon P is expressed as Y (Pu). The Y coordinates of other vertices Pb, PLi, PRj, Qu, Qb, QLm, and QRn are also expressed in the same manner.
[0006]
  Under the above conditions, for example, paying attention to each vertex QRn of the convex polygon Q, the following steps (1) to (3) are executed.
[0007]
  (1) From the vertices PLi, PRj of the convex polygon P, vertices PLi, PRj satisfying the following formula 1 are selected.
[0008]
[Expression 1]
Y (PLi-1) <Y (QRn) ≤Y (PLi)
Y (PRj + 1) <Y (QRn) ≦ Y (PRj)
  (2) It is determined whether or not the side (QRn, QRn + 1) of the convex polygon Q intersects any side of the convex polygon P, and when it intersects, the coordinates of the intersection are output.
[0009]
  (3) It is determined whether or not the vertex QRn of the convex polygon Q is located between the side (PLi−1, PLi) and the side (PRj, PRj + 1) of the convex polygon P, and the vertex QRn is When located between these sides, the coordinates of the vertex QRn are output.
[0010]
  For example, when attention is paid to the vertex QR2 of the convex polygon Q in FIG. 11 and the above steps (1) to (3) are executed, the vertices PLi, PRj satisfying the above equation 1 are PL3, Pb (PQ0 = Pb and ). Then, since the sides (QR2, QR3) of the convex polygon Q intersect with the sides (PL1, PL2) of the convex polygon P, the coordinates of the intersection A are output. Furthermore, since the vertex QR2 is located between the side (PL2, PL3) and the side (Pb, PR1), the coordinates of the vertex QR2 are output.
[0011]
  The above steps (1) to (3) are carried out for each vertex PLi, PRj, QLm, QRn, upper end point Pu, Qu and lower end point Pb, Qb of each convex polygon P, Q, thereby enclosing the overlapping portion R. The coordinates of each point to be output are output. For the upper end points Pu and Qu, only the above steps (1) and (3) are executed. And the coordinates of each output pointInThe figure corresponding to the overlapping portion R can be specified based on this, and the overlapping portion R can be cut out.
[0012]
  Note that the slab method considers a convex polygon as a set of trapezoids (slabs), and determines whether or not there is an intersection between slabs belonging to different convex polygons. It recognizes whether there is a part. Steps (1) to (3) described above show specific procedures when the graphic clipping process is realized based on this slab method.
[0013]
[Problems to be solved by the invention]
  By the way, if the above steps (1) to (3) are executed for each vertex of each convex polygon, theoretically, an overlapping portion of each convex polygon can be cut out. However, if the image clipping device is actually executed by causing the image processing device, the drawing device, or the graphic editing device to execute the above steps (1) to (3), there is a problem that the arithmetic processing takes time.
[0014]
  In particular, in the above step (3), it is determined whether or not the vertex of one polygon is located between two sides of the other polygon. This determination has a problem that it takes time for the arithmetic processing because it is necessary to perform the outer product calculation using the coordinates of the vertices and the coordinates of the end points of each side.
[0015]
  For example, if a convex polygon that is subject to graphic clipping processing has a complex shape and has a large number of vertices and sides, the outer product calculation must be performed many times to cut out the overlapping parts of each convex polygon. I must. Further, when a graphic to be subjected to graphic clipping processing includes a curve, the processing is usually performed by approximating the curve to many short straight lines. Even in such a case, the number of vertices and sides becomes enormous, and the number of times of outer product calculation becomes enormous. As a result, there is a problem in that the time for the arithmetic processing becomes long and the workability of image creation or editing may be reduced.
[0016]
  The present invention has been made in view of the above-described problems, and provides a graphic clipping device and a graphic clipping method capable of executing graphic clipping processing at high speed and improving the workability of graphic clipping work. It is an object.
[0017]
[Means for Solving the Problems]
  In order to solve the above-described problems, the invention of claim 1On the XY coordinate plane where the X-axis direction is the left-right direction and the Y-axis direction is the up-down directionA figure clipping device that cuts out a figure corresponding to an overlapping part of two convex polygons,SoOf each side of each convex polygon,An edge that can be traced clockwise from the top vertex that is the top vertex of each convex polygon to the bottom vertex that is the bottom vertexAttribute flags provided for the right side andAn edge that can be traced counterclockwise from the top vertex to the bottom vertex of each convex polygonAbout the left sideRespectivelyAn attribute flag provided,The twoConvex polygonalTop vertexOut ofUpper end located belowSelect a vertex as the initial vertex, and the initial vertex does not contain the initial vertexThe otherConvex polygonalSaidLeft side andSaidIt is determined whether or not it is located between the right side, and as a result of the determination, the initial vertex isThe otherWhen located between the left and right sides of the convex polygon, the coordinates of the initial vertex are output and the initial vertex is included.One ofConvex polygonalSaidThe attribute flag for the right-hand side andSaidSet the attribute flags for the left side to the ON state andThe otherConvex polygonalSaidThe attribute flag for the right-hand side andSaidThe attribute flags for the left side are each set to the OFF state, while the initial vertex isThe otherThe left and right sides of the convex polygonWhenIf not located between, include the initial vertexOne ofConvex polygonalSaidThe attribute flag for the right-hand side andSaidSet the attribute flags for the left side to OFF state respectivelyThe otherConvex polygonalSaidThe attribute flag for the right-hand side andSaidInitial setting means for setting the attribute flag for the left side to OFF state, two vertices on both sides of the initial vertex, and the initial vertexParallel to the X axisIntersect the lineSaidTwo sides of the other convex polygonEach of the two vertices that are the end points of each is located below4 vertices with vertices or last selected vertexIs located below and below the selected vertexVertices,It is a candidate for the previous selected vertex4 vertices with 3 vertices excluding the previous selected vertex from the selection candidate vertices,4 vertices of eitherTheOf this timeSelect candidate vertices,ConcernedOf the selection candidate verticesLocated at the topVertexThis timeVertex selection means for selecting as a selected vertex;Out of each side of the convex polygon that includes the selected vertex, the selected vertex and a vertex positioned above the selected vertex are end points.The side is the selected side,ConcernedOf the convex polygon that does not contain the selected vertexOut of each side, the selection candidate vertex and a vertex located above the selection candidate vertex are end points.Two sides andSaidThe selected side isRespectivelyAs a result of the determination by the intersection determination unit and the intersection determination unit that determines whether or not to intersect, when the selected side intersects the side of the convex polygon that does not include the selected vertex, the intersection point Output the coordinates of and for the edges that intersect each otherSaidIntersection point coordinate output means for inverting each attribute flag;Among the attribute flags, corresponding to the selected sideAttribute flag determining means for determining whether or not the attribute flag is in an ON state, vertex coordinate output means for outputting the coordinates of the selected vertex when the attribute flag is determined to be in the ON state by the attribute flag determining means, The coordinates of the selected vertex output by the vertex coordinate output means, the coordinates of the initial vertex when the initial setting means is output, and the coordinates of the intersection by the intersection coordinate output means A cutting means for cutting out a figure corresponding to an overlapped portion of the two convex polygons based on the coordinates;,It has.
[0018]
  That is, the two convex polygons are formed in, for example, the memory circuitXYIt is arranged on a coordinate plane, and graphic clipping processing is performed by scanning these convex polygons in a predetermined scanning direction. That meansXYOn the coordinate planeFrom top to bottomThe graphic clipping process proceeds toward this point.
[0019]
  Of the two convex polygons, one convex polygon, Each side that can trace clockwise from the top vertex, which is the top vertex, to the bottom vertex, which is the bottom vertex (passed when tracing counterclockwise from the bottom vertex to the top vertex) Each side)Is called the right side of one convex polygon, and each side of one convex polygon isEach side that can be traced counterclockwise from the top vertex to the bottom vertex (each side that passes when tracing counterclockwise from the top vertex to the bottom vertex)Is called the left side of one convex polygon. Then, an attribute flag for the right side of one convex polygon and an attribute flag for the left side of one convex polygon are provided. Here, the attribute flag is, for example, a flag provided on a rewritable recording circuit, and can store two types of states, an ON state and an OFF state.
[0020]
  Similarly, for the other convex polygon,Trace clockwise from top to bottomThe side is called the right side,Traces counterclockwise from top vertex to bottom vertexThe side is called the left side. Then, an attribute flag for the right side of the other convex polygon and an attribute flag for the left side of the one convex polygon are provided.
[0021]
  In this way, graphic clipping processing is performed using the four attribute flags.
[0022]
  Next, the initial setting meansTwoConvex polygonalTopOf the vertices,Upper end located belowSelect a vertex as the initial vertex. Further, the initial setting means is such that the initial vertex does not include the initial vertex.One ofIt is determined whether or not it is located between the left side and the right side of the convex polygon.
[0023]
  As a result of the determination, the initial vertex does not include the initial vertex.One ofWhen located between the left and right sides of a convex polygon, the coordinates of the initial vertex are output and the initial vertex is included.One ofSet the attribute flag for the right side of the convex polygon and the attribute flag for the left side to the ON state and do not include the initial vertexOne ofThe attribute flag for the right side and the attribute flag for the left side of the convex polygon are each set to the OFF state. On the other hand, the initial vertex does not include the initial vertexOne ofThe left and right sides of the convex polygonWhenIf the position is not between, the coordinates of the initial vertex are not output and the initial vertex is included.One ofThe attribute flag for the right side of the convex polygon and the attribute flag for the left side are both set to the OFF state and the initial vertex is not included.One ofThe attribute flag for the right side and the attribute flag for the left side of the convex polygon are each set to the OFF state.
[0024]
  Next, the vertex selection means selects a vertex to be subjected to a series of processing by the intersection determination means, the intersection coordinate output means, the attribute flag determination means, and the vertex coordinate output means, which will be described later, from each vertex of each convex polygon. Select as a vertex.
[0025]
  That is, a series of processes by the vertex selection unit, the intersection determination unit, the intersection coordinate output unit, the attribute flag determination unit, and the vertex coordinate output unit are repeatedly executed. Each time this series of processes is completed, the vertex selecting means sequentially selects new unprocessed vertices as selected vertices among the vertices of each convex polygon.
[0026]
  More specifically, immediately after the processing by the initial setting means is completed, the vertex selecting means passes two vertices adjacent to the initial vertex and the initial vertex.Parallel to the X axisTwo sides of the other convex polygon that intersects the lineEach of the two vertices that are the end points of each is located belowSelect a total of four vertices with vertices as selection candidate vertices, and select from these four selection candidate verticesLocated at the topSelect a vertex as the selected vertex. In addition, after a series of processes by the vertex selection unit, the intersection determination unit, the intersection coordinate output unit, the attribute flag determination unit, and the vertex coordinate output unit are executed at least once, the vertex selection unitIs located below and below the selected vertexA total of four vertices including the vertex and three vertices excluding the previous selected vertex from the selection candidate vertex (previous selection candidate vertex) are selected candidate vertices, and from among these four selection candidate verticesLocated at the topSelect a vertex as the selected vertex.
[0027]
  Next, the intersection determination meansThe selected vertex and the vertex located above the selected vertex are the end points.In a convex polygon whose side is the selected side and does not include the selected vertexThe selection candidate vertices and the vertices located above the selection candidate vertices are the end points.It is determined whether or not the two sides intersect with the selected side.
[0028]
  Next, the intersection coordinate output means, as a result of the determination by the intersection determination means, the selected side does not include the selected vertexOne ofWhen intersecting one of the two sides of the convex polygon, the coordinates of the intersection are output and the attribute flags for the intersecting sides are inverted. That is, when the attribute flag is in the OFF state, it is switched to the ON state. On the other hand, when the attribute flag is in the ON state, it is switched to the OFF state. In addition, the intersection coordinate output means, as a result of the determination by the intersection determination means, the selected side does not include the selected vertexOne ofWhen each of the two sides of the convex polygon intersects, the coordinates of each intersection are output and the attribute flags for the sides intersecting each other are inverted. As a result of the determination by the intersection determination means, the selected side does not include the selected vertex.One ofWhen it does not intersect any side of the convex polygon, the state of each attribute flag is maintained.
[0029]
  Next, the attribute flag determination meansCorresponds to the selected sideIt is determined whether or not the attribute flag is ON. Subsequently, the vertex coordinate output means outputs the coordinates of the selected vertex when the attribute flag is determined to be ON by the attribute flag determination means.
[0030]
  Then, a series of processes by the vertex selection means, the intersection determination means, the intersection coordinate output means, the attribute flag determination means, and the vertex coordinate output meansTheRun repeatedly.
[0031]
  Next, the cutting means outputs the coordinates of the selected vertex output by the vertex coordinate output means, the coordinates of the initial vertex when the coordinates of the initial vertex are output by the initial setting means, and the coordinates of the intersection by the intersection coordinate output means. If it is output, a figure corresponding to the overlapping portion of the two convex polygons is cut out based on the coordinates.
[0032]
  As described above, in the graphic clipping device described above, whether or not to output the coordinates of the selected vertex is determined based on the state of the attribute flag. The attribute flag is ON when the selected vertex of one convex polygon is inside the other convex polygon, and when the selected vertex of one convex polygon is outside the other convex polygon. , Set to be in the OFF state.
[0033]
  For example, in the initial setting means, when the initial vertex of one convex polygon is located between two sides of the other convex polygon, the attribute flag is set to the ON state. The initial vertex of one convex polygon is located between two sides of the other convex polygon, that is, the initial vertex of one convex polygon is located inside the other convex polygon Means that. Further, in the intersection coordinate output means, when the selected side intersects any side of the other convex polygon, the state of the attribute flag is inverted. The fact that the selected edge intersects one of the other convex polygons means that the selected vertex of one convex polygon is inside the other convex polygon, or one convex polygon is selected. It means that the vertex has come out from the inside of the other convex polygon.
[0034]
  Thus, the attribute flag is set to the ON state when the selected vertex of one convex polygon is located inside the other convex polygon. Therefore, if the coordinates of the selected vertex are output when the attribute flag is ON, the coordinates of each point surrounding the overlapping part of each convex polygon can be extracted, and the figure corresponding to the overlapping part Can be identified and cut out.
[0035]
  Thereby, in the initial setting means, when it is determined whether or not the initial vertex is located between the two sides of the other convex polygon, the cross product calculation is executed only once. Without doing anything, it is possible to extract the coordinates of each point that surrounds the overlapping portions of each convex polygon, and to cut out these overlapping portions. Accordingly, it is possible to reduce the calculation processing time in the graphic clipping process and improve the workability of the graphic clipping work.
[0036]
  Also, according to the graphic clipping method according to the second aspect of the present invention, similarly to the graphic clipping apparatus according to the first aspect of the present invention described above, it is possible to reduce the processing time in the graphic clipping process, and the workability of the graphic clipping work is improved. Can be improved.
[0037]
  Further, according to the invention of claim 3RecordRecording mediaRecorded programMake the computer read thisprogramBy causing the computer to execute the above, it is possible to cause the computer to function as the graphic clipping device according to the first aspect of the present invention.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0039]
  FIG. 1 shows a figure clipping device 10 according to an embodiment of the present invention. The graphic clipping device 10 performs a process of cutting out overlapping portions of a plurality of graphics, that is, a graphic clipping process.
[0040]
  As shown in FIG. 1, the graphic clipping device 10 includes a CPU 1, a ROM 2, a RAM 3, a display 4, a mouse 5, and a keyboard 6, which are connected to each other via a bus 7.
[0041]
  The CPU 1 performs overall control of the graphic clipping device 10. Further, the CPU 1 executes a graphic clipping processing program shown in FIGS. The ROM 2 stores a program for controlling the graphic clipping device 10 and a graphic clipping processing program shown in FIGS. An attribute flag 8 as shown in FIG. 2 is recorded in the RAM 3. The RAM 3 is used as a work area when performing graphic clipping processing. The display 4 displays a graphic or the like to be processed when performing graphic clipping processing, and the mouse 5 and the keyboard 6 are used to input commands and data to the graphic clipping device 10.
[0042]
  Next, graphic clipping processing will be described. In the following description, an example in which an overlapping portion of two convex polygons P and Q shown in FIG. 3 is cut out will be described.
[0043]
  In FIG. 3, the convex polygon P and the convex polygon Q arranged on the XY coordinate plane overlap each other. Here, the overlapping portion is defined as an overlapping portion R. Further, among the vertices of the convex polygon P, the vertex positioned at the top (vertex having the smallest Y coordinate) is set as the upper end point Pu, and the vertex positioned at the bottom (vertex having the largest Y coordinate) is set as the lower end point Pb. , PLi (i = 1, 2, 3,...) In the order of passing through the vertices that pass through each side of the convex polygon P counterclockwise from the upper end point Pu to the lower end point Pb. PRj (j = 1, 2, 3,... In order of passing through the vertices that pass through each side of the convex polygon P counterclockwise from the lower end point Pb toward the upper end point Pu. ). Similarly, among the vertices of the convex polygon Q, the top vertex is the upper end point Qu, the lowermost vertex is the lower end point Qb, and each side of the convex polygon Q is the lower end point from the upper end point Qu. Each vertex passing through when tracing counterclockwise toward the point Qb is defined as QLm (m = 1, 2, 3,...) In the order of passing, and each side of the convex polygon Q is defined from the lower end point Qb. Each vertex passing through when tracing counterclockwise toward the upper end point Qu is set to QRn (n = 1, 2, 3,...) In the order of passing. Further, the upper left corner of the figure is the origin of the XY coordinate plane.
[0044]
  For convenience of explanation, for example, the Y coordinate of the upper end point Pu of the convex polygon P is expressed as Y (Pu). The Y coordinates of other vertices Pb, PLi, PRj, Qu, Qb, QLm, and QRn are also expressed in the same manner. Further, each side that passes when the convex polygon P is traced counterclockwise from the upper end point Pu to the lower end point Pb is referred to as the left side of the convex polygon P, and is opposite to the upper end point Pu from the lower end point Pb. Each side that passes through when tracing clockwise is called the right side of the convex polygon P. Similarly, each side that passes when the convex polygon Q is traced counterclockwise from the upper end point Qu to the lower end point Qb is called the left side of the convex polygon Q, and the lower end point Qb is directed to the upper end point Qu. Each side that passes when it traces counterclockwise is called the right side of the convex polygon Q.
[0045]
  Further, the graphic clipping process uses a scanning line parallel to the X axis of the XY coordinate plane. By moving this scanning line along the Y axis from the small side of the Y coordinate value to the large side, a vertex output process or the like described later is performed. Hereinafter, the direction in which the scanning line moves is referred to as the scanning direction, the side with the small Y coordinate value is referred to as the scanning direction start side, and the side with the large Y coordinate value is referred to as the scanning direction end side or the scanning direction side.
[0046]
  Further, the attribute flag 8 shown in FIG. 2 is used for the graphic clipping process. The attribute flag 8 is composed of four flags indicating the left side state of the convex polygon P, the right side state of the convex polygon P, the left side state of the convex polygon Q, and the right side state of the convex polygon Q. Yes. These flags are set to the ON state or the OFF state, respectively, during the graphic clipping process.
[0047]
  The graphic clipping process will now be described with reference to the flowcharts of FIGS.
[0048]
  First, when an operator inputs graphic data corresponding to the convex polygons P and Q shown in FIG. 3 and a command for starting graphic clipping processing to the graphic clipping device 10, the CPU 1 applies the convex polygons P and Q to the convex polygons P and Q. Corresponding graphic data is stored in the work area of the RAM 3, and the main routine of graphic clipping processing shown in FIG. 5 is executed.
[0049]
  As shown in FIG. 5, first, the coordinates of each vertex, each upper end point, and each lower end point of the convex polygons P, Q are recognized based on the graphic data corresponding to the convex polygons P, Q (step 1). . At this time, as shown in FIG. 3, of the two convex polygons, the one having the smaller Y coordinate value of the upper end point is defined as a convex polygon P, and the one having the larger Y coordinate value of the upper end point is defined as the convex polygon Q. And
[0050]
  Next, it is determined whether or not the Y coordinate of the upper end point Qu of the convex polygon Q is larger than the Y coordinate of the lower end point Pb of the convex polygon P (step 2). . This is because when the Y coordinate of the upper end point Qu of the convex polygon Q is larger than the Y coordinate of the lower end point Pb of the convex polygon P, it can be determined that the convex polygon P and the convex polygon Q do not overlap. On the other hand, when the Y coordinate of the upper end point Qu of the convex polygon Q is not larger than the Y coordinate of the lower end point Pb of the convex polygon P, it can be determined that the convex polygon P and the convex polygon Q overlap. Therefore, first, the initial setting processing program shown in FIG. 6 is started to execute the initial setting processing (step 3).
[0051]
  In the initial setting process in FIG. 6, first, PLi and PRj satisfying the following mathematical formula 2 are obtained (step 11 and step 12).
[0052]
[Expression 2]
Y (PLi-1) <Y (QRn) ≤Y (PLi)
Y (PRj + 1) <Y (QRn) ≦ Y (PRj)
  Next, the left side (PLi−1, PLi) and the right side (PRj, PRj + 1) of the convex polygon P including PLi and PRj satisfying the above formula 2 are obtained, and the upper end point Qu (initial vertex) of the convex polygon Q ) Is positioned between these sides (step 13). When the upper end point Qu is located between these two sides, the coordinates of the upper end point Qu are output to a predetermined location in the storage area of the RAM 3 and the attribute flags on the left and right sides of the convex polygon Q are turned ON. Set (step 14 and step 15). On the other hand, when the upper end point Qu of the convex polygon Q is not located between these sides, the coordinates of the upper end point Qu are not output, and the attribute flags of the left side and the right side of the convex polygon Q are set to the OFF state ( Step 16).
[0053]
  Next, the attribute flags on the left and right sides of the convex polygon P are set to the OFF state (step 17), and the process proceeds to step 4 of the main routine shown in FIG.
[0054]
  In step 4 in FIG. 5, two vertices QLm, QRn on both sides of the upper end point Qu of the convex polygon Q and 2 of the convex polygon P that intersects the scanning line passing through the upper end point Qu of the convex polygon Q. A total of four vertices including two vertices PLi and PRj on the scanning direction side of the side are respectively selected as selection candidates. Further, the vertex having the smallest Y coordinate value is selected as the selected vertex from the four vertices selected as selection candidates. Then, the vertex output process shown in FIGS. 7 to 10 is started (step 5).
[0055]
  In the vertex output process, it is determined whether the selected vertex is one of the vertices PLi, PRj, QLm, and QRn (step 21 to step 23 in FIG. 7). When the selected vertex is the vertex PLi, the process proceeds to step 41 in FIG.
[0056]
  In step 41 in FIG. 8, among the left sides of the convex polygon P, the left side (PLi-1, PLi) having the selected vertex PLi on the scanning direction side is set as the selected side. Further, in the convex polygon Q, two sides having selection candidate vertices on the scanning direction side, that is, the right side (QRn, QRn + 1) and the left side (QLm-1, QLm) are set as processing target sides.
[0057]
  Next, it is determined whether or not the selected side (PLi−1, PLi) of the convex polygon P intersects the right side (QRn, QRn + 1) of the convex polygon Q set as the processing target side ( Step 42). When the selected side (PLi-1, PLi) of the convex polygon P intersects the right side (QRn, QRn + 1) of the convex polygon Q, the coordinates of the intersection are output and two intersecting ones are output. The attribute flag 8 is inverted (steps 43 and 44). On the other hand, when the selected side (PLi−1, PLi) of the convex polygon P does not intersect the right side (QRn, QRn + 1) of the convex polygon Q, the attribute flag 8 is not inverted.
[0058]
  Next, it is determined whether or not the selected side (PLi-1, PLi) of the convex polygon P intersects the left side (QLm-1, QLm) of the convex polygon Q set as the processing target side ( Step 45). When the selected side (PLi-1, PLi) of the convex polygon P intersects the left side (QLm-1, QLm) of the convex polygon Q, the coordinates of the intersection are output and two intersecting ones are output. The attribute flag 8 is inverted (step 46 and step 47). On the other hand, when the selected side (PLi-1, PLi) of the convex polygon P does not intersect the left side (QLm-1, QLm) of the convex polygon Q, the attribute flag is not inverted.
[0059]
  Next, it is determined whether or not the attribute flag 8 on the left side of the convex polygon P is in an ON state. When the attribute flag 8 is in the ON state, the coordinates of the vertex PLi selected as the selected vertex are placed in a predetermined location in the storage area of the RAM 3. Output (step 48 and step 49). On the other hand, when the attribute flag 8 on the left side of the convex polygon P is OFF, the coordinates of the vertex PLi are not output.
[0060]
  On the other hand, when the selected vertex is the vertex PRj, the routine proceeds to step 51 in FIG. In step 51 in FIG. 9, the right side (PRj, PRj + 1) having the selected vertex PRj on the scanning direction side is set as the selected side from among the right sides of the convex polygon P. Further, in the convex polygon Q, two sides having selection candidate vertices on the scanning direction side, that is, the left side (QLm−1, QLm) and the right side (QRn, QRn + 1) are set as processing target sides.
[0061]
  Next, it is determined whether or not the selected side (PRj, PRj + 1) of the convex polygon P intersects the left side (QLm-1, QLm) of the convex polygon Q set as the processing target side ( Step 52). When the selected side (PRj, PRj + 1) of the convex polygon P intersects the left side (QLm-1, QLm) of the convex polygon Q, the coordinates of the intersection are output and two intersecting ones are output. The attribute flag 8 is inverted (step 53 and step 54). On the other hand, when the selected side (PRj, PRj + 1) of the convex polygon P does not intersect the left side (QLm-1, QLm) of the convex polygon Q, the attribute flag 8 is not inverted.
[0062]
  Next, it is determined whether or not the selected side (PRj, PRj + 1) of the convex polygon P intersects the right side (QRn, QRn + 1) of the convex polygon Q set as the processing target side ( Step 55). When the selected side (PRj, PRj + 1) of the convex polygon P intersects with the right side (QRn, QRn + 1) of the convex polygon Q, the coordinates of the intersection are output and two intersecting each other The attribute flag 8 is inverted (step 56 and step 57). On the other hand, when the selected side (PRj, PRj + 1) of the convex polygon P does not intersect the right side (QRn, QRn + 1) of the convex polygon Q, the attribute flag is not inverted.
[0063]
  Next, it is determined whether or not the attribute flag 8 on the right side of the convex polygon P is in an ON state. When the attribute flag 8 is in an ON state, the coordinates of the vertex PRj selected as the selected vertex are placed in a predetermined location in the storage area of the RAM 3. Output (step 58 and step 59). On the other hand, when the attribute flag 8 on the right side of the convex polygon P is OFF, the coordinates of the vertex PRj are not output.
[0064]
  On the other hand, when the selected vertex is the vertex QLm, the routine proceeds to step 61 in FIG. In step 61 in FIG. 10, the left side (QLm−1, QLm) having the selected vertex QLm on the scanning direction side is set as the selected side from the left sides of the convex polygon Q. Furthermore, two sides having a selection candidate vertex on the scanning direction side in the convex polygon P, that is, the right side (PRj, PRj + 1) and the left side (PLi-1, PLi) are set as processing target sides.
[0065]
  Next, it is determined whether or not the selected side (QLm-1, QLm) of the convex polygon Q intersects the right side (PRj, PRj + 1) of the convex polygon P set as the processing target side ( Step 62). When the selected side (QLm-1, QLm) of the convex polygon Q intersects the right side (PRj, PRj + 1) of the convex polygon P, the coordinates of the intersection are output and two intersecting ones are output. The attribute flag 8 is inverted (step 63 and step 64). On the other hand, when the selected side (QLm-1, QLm) of the convex polygon Q does not intersect the right side (PRj, PRj + 1) of the convex polygon P, the attribute flag 8 is not inverted.
[0066]
  Next, it is determined whether or not the selected side (QLm-1, QLm) of the convex polygon Q intersects the left side (PLi-1, PLi) of the convex polygon P set as the processing target side ( Step 65). When the selected side (QLm-1, QLm) of the convex polygon Q intersects the left side (PLi-1, PLi) of the convex polygon P, the coordinates of the intersection are output and two intersecting ones are output. The attribute flag 8 is inverted (step 66 and step 67). On the other hand, when the selected side (QLm-1, QLm) of the convex polygon Q does not intersect the left side (PLi-1, PLi) of the convex polygon P, the attribute flag is not inverted.
[0067]
  Next, it is determined whether or not the attribute flag 8 on the left side of the convex polygon Q is in the ON state. If the attribute flag 8 is in the ON state, the coordinates of the vertex QLm selected as the selected vertex are placed in a predetermined location in the storage area of the RAM 3. Output (step 68 and step 69). On the other hand, when the attribute flag 8 on the left side of the convex polygon Q is in the OFF state, the coordinates of the vertex QLm are not output.
[0068]
  On the other hand, when the selected vertex is the vertex QRn, the routine proceeds to step 24 in FIG. In step 24 in FIG. 7, the right side (QRn, QRn + 1) having the selected vertex QRn on the scanning direction side is set as the selected side from among the right sides of the convex polygon Q. Further, in the convex polygon P, two sides having selection candidate vertices on the scanning direction side, that is, the left side (PLi-1, PLi) and the right side (PRj, PRj + 1) are set as processing target sides.
[0069]
  Next, it is determined whether or not the selected side (QRn, QRn + 1) of the convex polygon Q intersects the left side (PLi-1, PLi) of the convex polygon P set as the processing target side ( Step 25). When the selected side (QRn, QRn + 1) of the convex polygon Q intersects the left side (PLi-1, PLi) of the convex polygon P, the coordinates of the intersection are output and two intersecting ones are output. The attribute flag 8 is inverted (steps 26 and 27). On the other hand, when the selected side (QRn, QRn + 1) of the convex polygon Q does not intersect the left side (PLi-1, PLi) of the convex polygon P, the attribute flag 8 is not inverted.
[0070]
  Next, it is determined whether or not the selected side (QRn, QRn + 1) of the convex polygon Q intersects the right side (PRj, PRj + 1) of the convex polygon P set as the processing target side ( Step 28). When the selected side (QRn, QRn + 1) of the convex polygon Q intersects the right side (PRj, PRj + 1) of the convex polygon P, the coordinates of the intersection are output and two intersecting ones are output. The attribute flag 8 is inverted (step 29 and step 30). On the other hand, when the selected side (QRn, QRn + 1) of the convex polygon Q does not intersect the right side (PRj, PRj + 1) of the convex polygon P, the attribute flag is not inverted.
[0071]
  Next, it is determined whether or not the attribute flag 8 on the right side of the convex polygon Q is in an ON state. When the attribute flag 8 is in an ON state, the coordinates of the vertex QRn selected as the selected vertex are placed in a predetermined location in the storage area of the RAM 3. Output (step 31 and step 32). On the other hand, when the attribute flag 8 on the right side of the convex polygon Q is OFF, the coordinates of the vertex QRn are not output.
[0072]
  When the vertex output processing shown in FIGS. 7 to 10 is completed, the process proceeds to step 6 of the main routine shown in FIG.
[0073]
  In step 6 in FIG. 6, it is determined whether or not the selected vertex is the lower end point Pb of the convex polygon P or the lower end point Qb of the convex polygon Q. When the selected vertex is not the lower end point Pb or the lower end point Qb, the process returns to step 4.
[0074]
  Then, in step 4, the vertex that has been selected as the selected vertex so far is excluded from the selection candidates, and instead, a vertex that is located next to the vertex that has been selected as the selected vertex so far in the Y-axis direction is a new selection candidate. Add to. That is, when the vertex selected so far is the vertex PLi, the vertex PLi is excluded from the selection candidates, and the vertex PLi + 1 is newly added to the selection candidates. If the vertex selected so far is the vertex PRj, the vertex PRj is excluded from the selection candidates, and the vertex PRj-1 is newly added to the selection candidates. Further, when the vertex selected so far is the vertex QLm, the vertex QLm is excluded from the selection candidates, and the vertex QLm + 1 is newly added to the selection candidates. Furthermore, when the vertex selected so far is the vertex QRn, the vertex QRn is excluded from the selection candidates, and the vertex QRn-1 is newly added to the selection candidates. Further, in step 4, a vertex having the smallest Y coordinate value is newly selected as a selected vertex from the four vertices selected as selection candidates. Then, the vertex output process shown in FIGS. 7 to 10 is started again (step 5).
[0075]
  In this way, by repeating the processing from step 4 to step 6, the vertex output processing proceeds from the processing start side to the end side along the scanning direction as shown by the arrow in FIG. That is, the vertices of the convex polygons P and Q shown in FIG. 3 are sequentially selected as the selected vertices in ascending order of the Y coordinate value, and are subjected to vertex output processing. When the lower end point Pb or the lower end point Qb is selected as the selected vertex, “YES” is determined in the step 6, and the process proceeds to the step 7. At this stage, the coordinates of the vertices surrounding the overlapping portion R of the convex polygon P and the convex polygon Q are output to a predetermined location in the storage area of the RAM 3.
[0076]
  In step 7, the overlapping portion R is cut out based on the coordinates of each vertex output to a predetermined location in the storage area of the RAM 3.
[0077]
  Next, the operation of actually cutting out the overlapping portion R of the convex polygons P and Q shown in FIG. 3 will be described with reference to the attribute flag history shown in FIG.
[0078]
  First, since the Y coordinate of the upper end point Qu of the convex polygon Q is not larger than the Y coordinate of the lower end point Pb of the convex polygon P, an initial setting process is executed (step 2 and step 3). In the initial setting process, the upper end points Qu (initial vertices) satisfy Pli and PRj satisfying the above-described equation 2, that is, the left side (PL1, PL2) and the right side (PR2, PR3) of the convex polygon P including PL2 and PR2. (Step 11 to step 13). As a result of this determination, since the upper end point Qu is not located between the left side (PL1, PL2) and the right side (PR2, PR3), the coordinates of the upper end point Qu are not output, and the left and right sides of the convex polygon P and The attribute flags 8 on the left and right sides of the convex polygon Q are set to the OFF state as shown in FIG. 4 (steps 16 and 17).
[0079]
  Next, two vertices QL1, QR3 on both sides of the upper end point Qu of the convex polygon Q, and the two sides of the convex polygon P intersecting the scanning line passing through the upper end point Qu of the convex polygon Q have a scanning direction side. A total of four vertices of the two vertices PL2 and PR2 are selected as selection candidates. Further, the vertex PR2 is selected as the selected vertex from the four vertices, and the vertex output process is executed on the vertex PR2 (step 4 and step 5). In the vertex output process, first, the right side (PR2, PR3) of the convex polygon P is set as the selected side, and the left side (Qu, QL1) and the right side (QR3, Qu) of the convex polygon Q are set as the processing target sides. It is set (step 51). Next, it is determined whether or not the selected side (PR2, PR3) of the convex polygon P intersects the left side (Qu, QL1) of the convex polygon Q (step 52). As shown in FIG. 3, the selected side (PR2, PR3) of the convex polygon P does not intersect the left side (Qu, QL1) of the convex polygon Q. It is determined whether or not PR3) intersects the right side (QR3, Qu) of the convex polygon Q (step 55). As shown in FIG. 3, the selected side (PR2, PR3) of the convex polygon P does not intersect with the right side (QR3, Qu) of the convex polygon Q, so the right side (selected side) of the convex polygon P is next. It is determined whether or not the attribute flag is ON (step 58). As shown in FIG. 4, since the attribute flag 8 on the right side of the convex polygon P is in the OFF state, the coordinates of the vertex PR2 are not output.
[0080]
  Next, among the vertices of the convex polygons P and Q, vertices PL2, PR1, QL1, and QR3 are selected as selection candidates. Further, the vertex QR3 is selected as the selected vertex from the four vertices, and the vertex output process is executed on the vertex QR3 (steps 4 and 5). In the vertex output process, first, the right side (QR3, Qu) of the convex polygon Q is set as the selected side, and the left side (PL1, PL2) and the right side (PR1, PR2) of the convex polygon P are set as the processing target sides. It is set (step 24). Next, it is determined whether or not the selected side (QR3, Qu) of the convex polygon Q intersects the left side (PL1, PL2) of the convex polygon P (step 25). As shown in FIG. 3, the selected side (QR3, Qu) of the convex polygon Q does not intersect the left side (PL1, PL2) of the convex polygon P. It is determined whether or not Qu) intersects the right side (PR1, PR2) of the convex polygon P (step 28). As shown in FIG. 3, the selected side (QR3, Qu) of the convex polygon Q does not intersect with the right side (PR1, PR2) of the convex polygon P. Next, the right side (selected side) of the convex polygon Q It is determined whether or not the attribute flag is ON (step 31). As shown in FIG. 4, since the attribute flag 8 on the right side of the convex polygon Q is in the OFF state, the coordinates of the vertex QR3 are not output.
[0081]
  Next, among the vertices of the convex polygons P and Q, vertices PL2, PR1, QL1, and QR2 are selected as selection candidates. Further, the vertex QL1 is selected as the selected vertex from the four vertices, and the vertex output process is executed on the vertex QL1 (step 4 and step 5). In the vertex output process, first, the left side (Qu, QL1) of the convex polygon Q is set as the selected side, and the right side (PR1, PR2) and the left side (PL1, PL2) of the convex polygon P are set as the processing target side. It is set (step 61). Next, it is determined whether or not the selected side (Qu, QL1) of the convex polygon Q intersects the right side (PR1, PR2) of the convex polygon P (step 62). As shown in FIG. 3, since the selected side (Qu, QL1) of the convex polygon Q does not intersect the right side (PR1, PR2) of the convex polygon P, the selected side (Qu, Q, It is determined whether QL1) intersects the left side (PL1, PL2) of the convex polygon P (step 65). As shown in FIG. 3, the selected side (Qu, QL1) of the convex polygon Q does not intersect with the left side (PL1, PL2) of the convex polygon P. Next, the left side (selected side) of the convex polygon Q It is determined whether or not the attribute flag is ON (step 68). As shown in FIG. 4, since the attribute flag 8 on the left side of the convex polygon Q is in the OFF state, the coordinates of the vertex QL1 are not output.
[0082]
  Next, of the vertices of the convex polygons P and Q, the vertices PL2, PR1, QL2, and QR2 are selected as selection candidates. Further, the vertex PL2 is selected as the selected vertex from the four vertices, and the vertex output process is executed on the vertex PL2 (step 4 and step 5). In the vertex output process, first, the left side (PL1, PL2) of the convex polygon P is set as the selected side, and the right side (QR2, QR3) and the left side (QL1, QL2) of the convex polygon Q are set as the processing target side. It is set (step 41). Next, it is determined whether or not the selected side (PL1, PL2) of the convex polygon P intersects the right side (QR2, QR3) of the convex polygon Q (step 42). As shown in FIG. 3, since the selected side (PL1, PL2) of the convex polygon P intersects the right side (QR2, QR3) of the convex polygon Q at the intersection A, the coordinates of the intersection A are output. At the same time, the attribute flags 8 on the left side (selected side) of the convex polygon P and the right side of the convex polygon Q are inverted to the ON state (step 43 and step 44). Next, it is determined whether or not the selected side (PL1, PL2) of the convex polygon P intersects the left side (QL1, QL2) of the convex polygon Q (step 45). As shown in FIG. 3, since the selected sides (PL1, PL2) of the convex polygon P do not intersect the left sides (QL1, QL2) of the convex polygon Q, next, the left side (selected side) of the convex polygon P It is determined whether or not the attribute flag is ON (step 48). As shown in FIG. 4, since the attribute flag on the left side of the convex polygon Q is in the ON state, the coordinates of the vertex PL2 are output (step 49).
[0083]
  Similarly, vertices PR1, QL2, QR2, PL3, PL4, and QR1 are sequentially selected as selected vertices in this order, and the vertex output process is repeatedly executed. In the process, the coordinates of the vertex QR2, the coordinates of the vertex PL3, and the coordinates of the intersection B of the left side (PL3, PL4) of the convex polygon P and the right side (QR1, QR2) of the convex polygon Q are output. Thereafter, when the lower end point Pb is selected as the selected vertex, “YES” is determined in the step 6, the process proceeds to the step 7, and the cutting process is executed in the step 7. At this stage, the coordinates of all the vertices surrounding the overlapping portion R, that is, the coordinates of the vertex PL2, the vertex PL3, the vertex QR2, the intersection point A, and the intersection point B are output to a predetermined place in the recording area of the RAM 3. Therefore, the overlapping portion R is cut out based on these coordinates.
[0084]
  Thus, according to the graphic clipping device 10 according to the present embodiment, whether or not to output the coordinates of the selected vertex is determined based on the state of the attribute flag 8. The attribute flag 8 is ON when the selected vertex of one convex polygon is inside the other convex polygon, and the selected vertex of one convex polygon is outside the other convex polygon. Sometimes it is set to be in the OFF state.
[0085]
  For example, in the initial setting process, when the upper end point Qu of the convex polygon Q is located between the left side and the right side of the convex polygon P that includes the vertices PLi and PRj satisfying the above formula 2, the attribute flag 8 is ON. Set to state. The upper end point Qu of the convex polygon Q is located between the left side and the right side of the convex polygon P. That is, the upper end point Qu of the convex polygon Q is located inside the convex polygon P. Means. In the vertex output processing, when the side of one convex polygon including the selected vertex intersects either one of the left side and the right side of the other convex polygon, the state of the attribute flag is inverted. The side of one convex polygon that includes the selected vertex intersects the side of the other convex polygon means that the selected vertex of one convex polygon is inside the other convex polygon, or This means that the selected vertex of one convex polygon has gone out of the inside of the other convex polygon.
[0086]
  Thus, the attribute flag 8 is set to the ON state when the selected vertex of one convex polygon is located inside the other convex polygon. Therefore, when the coordinates of the selected vertex are output when the attribute flag is ON, the coordinates of the vertices surrounding the overlapping portion R of the convex polygons P and Q can be extracted. The overlapping portion R can be cut out based on the coordinates.
[0087]
  Thereby, in the initial setting process, when determining whether or not the upper end point Qu of the convex polygon Q is located between the left side and the right side of the convex polygon P, the outer product calculation is executed only once. Thereafter, the coordinates of each point surrounding the overlapping portion R of the convex polygons P and Q can be extracted by referring to the attribute flag 8 without performing any outer product calculation, and the overlapping portion R is cut out. be able to. Accordingly, it is possible to reduce the calculation processing time in the graphic clipping process and improve the workability of the graphic clipping work.
[0088]
  In the above embodiment, the graphic clipping process is executed in the Y-axis direction from the upper end point Qu of the convex polygon Q toward the lower end point Pb of the convex polygon P. However, the present invention is not limited to this, and the graphic clipping is not limited thereto. The process may be executed in the Y-axis direction from the lower end point Pb of the convex polygon P toward the upper end point Qu of the convex polygon Q, and the graphic clipping process may be executed in the X-axis direction.
[0089]
  In the above embodiment, the graphic clipping processing program is stored in the ROM 2. However, the present invention is not limited to this, and the graphic clipping processing program is read from the outside into the graphic clipping device 10 and stored in the RAM 3 or the like. It is good also as a structure. Further, the graphic clipping processing program may be recorded on a recording medium such as a CD-ROM or a floppy disk, and the graphic clipping processing program may be read by the computer via the recording medium so that the computer functions as a graphic clipping device.
[0090]
  Steps 11 to 17 in FIG. 6 are specific examples of the initial setting means. Step 4 in FIG. 5 is a specific example of the vertex selecting means, step 24, step 25 and step 28 in FIG. 7, step 41, step 42 and step 45 in FIG. 8, step 51 in FIG. 52 and step 55, and step 61, step 62 and step 65 in FIG. 10 are specific examples of the intersection determination means. Step 26, Step 27, Step 29 and Step 30 in FIG. 7, Step 43, Step 44, Step 46 and Step 47 in FIG. 8, Step 53, Step 54, Step 56 and Step 57 in FIG. Steps 63, 64, 66 and 67 in the middle are specific examples of the intersection coordinate output means. Step 31 in FIG. 7, step 48 in FIG. 8, step 58 in FIG. 9, and step 68 in FIG. 10 are specific examples of the attribute flag determination means. Step 32 in FIG. 7 and step in FIG. 49, step 59 in FIG. 9, and step 69 in FIG. 10 are specific examples of the vertex coordinate output means. Step 7 in FIG. 5 is a specific example of the cutting means.
[0091]
【The invention's effect】
  As described above in detail, according to the graphic clipping device of the first aspect of the present invention, when the selected vertex of one convex polygon is located inside the other convex polygon, it is set to the ON state, and one convex polygon Since the attribute flag that is set to the OFF state is provided when the selected vertex of the square is located outside the other convex polygon, the coordinates of the selected vertex are output when this attribute flag is ON. At the time of setting, when determining whether or not the initial vertex is located between the two sides of the other convex polygon, the outer product calculation is executed only once, but thereafter no outer product calculation is performed. The coordinates of the points surrounding the overlapping portions of the convex polygons can be extracted, and the overlapping portions can be cut out. Accordingly, it is possible to reduce the calculation processing time in the graphic clipping process and improve the workability of the graphic clipping work.
[0092]
  In particular, when a graphic to be subjected to graphic clipping processing includes a curve, processing is normally performed by approximating the curve to a number of short straight lines, and therefore the number of vertices to be processed becomes enormous. In such a case, the calculation processing time in the graphic clipping process can be greatly reduced, and the graphic clipping process can be speeded up.
[0093]
  Also, according to the graphic clipping method according to the second aspect of the present invention, similarly to the graphic clipping apparatus according to the first aspect of the present invention described above, it is possible to reduce the processing time in the graphic clipping process, and the workability of the graphic clipping work is improved. Can be improved.
[0094]
  Further, according to the invention of claim 3RecordRecording mediaRecorded programMake the computer read thisprogramBy causing the computer to execute, the computer can function as the graphic clipping device according to the first aspect of the present invention, and the same effect as the graphic clipping device according to the first aspect of the present invention can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a graphic clipping device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing attribute flags according to the embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a convex polygon that is a target of graphic clipping processing according to the embodiment of the present invention;
FIG. 4 is an explanatory diagram showing a history of attribute flags in the embodiment of the present invention.
FIG. 5 is a flowchart showing a main routine of graphic clipping processing in the embodiment of the present invention.
FIG. 6 is a flowchart showing an initial setting process in the embodiment of the present invention.
FIG. 7 is a flowchart showing vertex output processing according to the embodiment of the present invention.
FIG. 8 is a flowchart showing vertex output processing according to the embodiment of the present invention.
FIG. 9 is a flowchart showing vertex output processing according to the embodiment of the present invention.
FIG. 10 is a flowchart showing vertex output processing according to the embodiment of the present invention.
FIG. 11 is an explanatory diagram showing a convex polygon that is a target of graphic clipping processing;
[Explanation of symbols]
  1 CPU
  2 ROM
  3 RAM
  8 attribute flags
  10 figure clipping device
  P, Q Convex polygon

Claims (3)

A figure clipping device that cuts out a figure corresponding to an overlapping portion of two convex polygons on an XY coordinate plane having an X-axis direction as a horizontal direction and a Y-axis direction as a vertical direction ,
Its out of the sides of the convex polygon respectively, edges can be traced from the upper end vertex the vertex located on top of each convex polygon and the lower end vertex the vertex located in the lowermost clockwise and attribute flag provided respectively for the left side is a side of and attribute flag provided respectively from the upper apex of each convex polygon to said lower apex can be traced counterclockwise about the right-hand side is,
Among the upper apex of said two convex polygons, select the upper vertices located more downward as the initial vertex, the initial vertex of the left side and the right side of the other convex polygons do not contain the initial vertex Whether the initial vertex is located between the left side and the right side of the other convex polygon, and outputs the coordinates of the initial vertex, and the attribute flag and the left side of the said right-hand side of the other convex polygons as well as set the attribute flag to each oN state for the attribute flag and the left side for said right-hand side of the convex polygon of a direction which includes an initial vertex set the attribute flag to each OFF state for, whereas, when the initial vertex is not located between the left and right sides of the convex polygon of the other, including the initial vertex The attribute flag and the attributes of the left side of the right side of the other convex polygons as well as set the attribute flag to each OFF state for the attribute flag and the left side for said right-hand side of the convex polygon of square Initial setting means for setting each flag to an OFF state;
Two vertices on both sides of the initial vertex, Ri through the initial vertex and the two vertices are two sides respectively of the end points of the other convex polygons which intersect with a line parallel to the X axis, Four vertices with each of the vertices positioned below , or a vertex that is adjacent to the previous selected vertex and positioned below the selected vertex, and a selection candidate vertex that is a candidate for the previous selected vertex the four vertices one of the four vertices of the three vertices excluding the selected vertex of the previous and the current selected candidate vertices from this time of the selected vertex vertices located on top of the selected candidate vertices Vertex selection means to select as,
Of the sides of the convex polygon towards containing the selected vertices, the edges of the vertex which is located above the said selected vertex and the selected vertex and end points and the selected edge, convex towards not including the selected vertex of the sides of the polygon, the intersection determining means for determining whether the two sides with the selected edge to the vertex endpoints located above said selected candidate vertex and the selected candidate apex intersects each When,
As a result of the determination by the intersection determination means, when the selected side intersects with the side of the convex polygon that does not include the selected vertex, the coordinates of the intersection point are output each time, and the sides that intersect with each other are output. and the intersection point coordinate output means for inverting the attribute flag, respectively,
Among the attribute flags, attribute flag determination means for determining whether or not an attribute flag corresponding to the selected side is in an ON state;
Vertex coordinate output means for outputting the coordinates of the selected vertex when the attribute flag is determined to be ON by the attribute flag determination means;
The coordinates of the selected vertex output by the vertex coordinate output means, the coordinates of the initial vertex when the coordinates of the initial vertex are output by the initial setting means, and the coordinates of the intersection point are output by the intersection coordinate output means. A cutting means for cutting out a figure corresponding to the overlapping portion of the two convex polygons based on the coordinates ,
A figure clipping device comprising: A graphic clipping method for cutting out a graphic corresponding to an overlapping portion of two convex polygons on an XY coordinate plane with the X-axis direction being the left-right direction and the Y-axis direction being the vertical direction ,
Control means, out of the upper end vertex is a vertex located at the two convex polygons each top, select the upper vertices located more downward as the initial vertex and the other of which the initial vertex does not include the initial vertex Trace the left side that can trace counterclockwise from the top vertex of the convex polygon to the bottom vertex that is the lowest vertex and the clockwise direction from the top vertex to the bottom vertex of the convex polygon It is determined whether or not the first vertex is located between the left side and the right side of the other convex polygon, as a result of the determination . and attribute flag of the attribute flag and the right side of the said left-hand side of a convex polygon, respectively, the initial storage means for storing a coordinate of each vertex of the figure corresponding to the two overlapping portions of a convex polygon And outputs coordinates of the point, and then the attribute flags for the attribute flag and the left side for said right-hand side of the convex polygon towards containing the initial vertex to the respective ON state of the other as well as set in the storage means the attribute flags for the attribute flag and the left side for said right-hand side of the convex polygon, respectively in the OFF state is set in the storage means, whereas, during the initial vertex of the left and right sides of the convex polygon of the other when not located in the include the initial vertex with set attributes flags and attributes flag for the left side in the storage means in the OFF state, respectively for the right side of the convex polygon towards containing the initial vertex no person for the right side of the convex polygon attribute flags and attributes flag for the left and each OFF state the storage And the initial setting step of setting the stage,
It said control means, and two vertices on both sides of the initial vertex, Ri through the initial vertex, and a second side respectively of the end points of the other convex polygons which intersect with a line parallel to the X axis 2 4 vertices with each of the vertices located below , or adjacent to the previous selected vertex and positioned below the selected vertex, and candidates for the previous selected vertex four vertices from the selection candidate vertices and three vertices excluding the selected vertex of the previous, the one of the four vertices of the current selected candidate vertices is, the vertices located on the top among the selected candidate vertices Vertex selection step for selecting as the selected vertex this time ,
It said control means, one of each side towards the convex polygon including the selected vertex and the sides to the apex end point which is located above the said selected vertex and the selected vertex and the selected edge, the selection vertices of convex polygon sides towards free, determining whether the two sides with the selected edge to the vertex endpoints located above said selected candidate vertex and the selected candidate apex intersects each An intersection determination step,
As a result of the determination in the intersection determination step , the control means outputs the coordinates of the intersection to the storage means each time the selected edge intersects the side of the convex polygon that does not include the selected vertex. And an intersection coordinate output step for inverting the attribute flags set in the storage means for the sides intersecting each other,
An attribute flag determination step in which the control means determines whether or not an attribute flag corresponding to the selected side among the attribute flags set in the storage means is ON;
A vertex coordinate output step of outputting the coordinates of the selected vertex to the storage means when the control means determines that the attribute flag is ON in the attribute flag determination step;
The control means repeatedly executes the vertex selection step, the intersection determination step, the intersection coordinate output step, and the vertex coordinate output step, and the coordinates of the selected vertex output in the vertex coordinate output step, the initial setting step in the initial setting step. When the coordinates of the vertex are output, and when the coordinates of the intersection are output in the intersection coordinates output step, the coordinates correspond to the overlapping portions of the two convex polygons based on the coordinates. A cutting step to cut out the figure ;
A figure clipping method comprising: A computer that executes a graphic clipping process for cutting out a graphic corresponding to an overlapping portion of two convex polygons on an XY coordinate plane in which the X-axis direction is the left-right direction and the Y-axis direction is the vertical direction ;
A vertex located at the two convex polygons each of the uppermost of the upper vertices, more the upper vertex located below selected as initial vertices, the initial vertices of the other convex polygons do not contain the initial vertex can be traced from the upper apex of the left side and the convex polygon is a side that can and this follow up bottom vertex is vertices located in the lowermost from the upper apex counterclockwise until the lower end apex clockwise It is determined whether or not it is positioned between the right side that is the side, and when the initial vertex is positioned between the left side and the right side of the other convex polygon as a result of the determination, the two convex polygons and attribute flag of the attribute flag and the right-hand side for each of the left, the coordinates of each vertex of the figure corresponding to the two convex polygons of overlapping portions, the initial coordinates of vertices in the storage means for storing And force, and, of the other convex polygons with setting the attribute flag in the storage means after each ON state for the attribute flag and the left side for said right-hand side of the convex polygon towards containing the initial vertex and the attribute flags for the attribute flag and the left side for said right side, respectively the OFF state is set in the storage means, whereas, when the initial vertex is not located between the left and right sides of the convex polygon of the other , convex towards not including the initial vertex with set attributes flags and attributes flag for the left side in the storage means in the OFF state, respectively for the right side of the convex polygon towards containing the initial vertex set in the storage means attribute flag for the attribute flag and the left side for said right-hand side of the polygon, respectively in the OFF state Initial setting means that,
Two vertices on both sides of the initial vertex, Ri through the initial vertex and the two vertices are two sides respectively of the end points of the other convex polygons which intersect with a line parallel to the X axis, Four vertices with each of the vertices positioned below , or a vertex that is adjacent to the previous selected vertex and positioned below the selected vertex, and a selection candidate vertex that is a candidate for the previous selected vertex the four vertices one of the four vertices of the three vertices excluding the selected vertex of the previous and the current selected candidate vertices from this time of the selected vertex vertices located on top of the selected candidate vertices Vertex selection means to select as,
Of the sides of the convex polygon towards containing the selected vertices, the edges of the vertex which is located above the said selected vertex and the selected vertex and end points and the selected edge, convex towards not including the selected vertex among polygonal sides, intersection determination means for determining whether the two sides with the selected edge to the vertex endpoints located above said selected candidate vertex and the selected candidate apex intersects respectively,
As a result of the determination by the intersection determination means , when the selected side intersects with the side of the convex polygon that does not include the selected vertex, the coordinates of the intersection point are output to the storage means and intersect each other. Intersection point coordinate output means for inverting the attribute flag set in the storage means for each side to be
Attribute flag determination means for determining whether or not an attribute flag corresponding to the selected side among the attribute flags set in the storage means is ON;
Vertex coordinate output means for outputting the coordinates of the selected vertex to the storage means when the attribute flag is determined to be ON by the attribute flag determination means ; and
Before SL vertex coordinate output means and said selecting vertices of coordinates output by the its coordinates if the initial setting unit by the coordinate of the initial vertex is output, and the coordinates of the intersection points outputted by the intersection coordinate output means A cutting means for cutting out a figure corresponding to the overlapping portion of the two convex polygons based on the coordinates when
A recording medium on which a program that functions as a computer is recorded so as to be readable by a computer .

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