JP3436008B2 - Drawing processing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drawing processing apparatus for carrying out drawing processing for output from a printer, a graphic display device or the like, based on graphic data created by a computer.

[0002]

2. Description of the Related Art In order to output a graphic created by a computer from a printer or a graphic display device, it is generally necessary to develop graphic data such as vector information held by the computer into a bit map image.
The development into such a bitmap image is called drawing processing.

One of the basic processes in the drawing process is
There is a closed area fill. The closed region refers to a region surrounded by a closed curve composed of straight lines and curved lines, and the filling refers to painting pixels in such a closed region with a constant color. The filling process is sometimes called scan conversion (scan conversion).

One of the methods for filling closed areas is, for example, "Computer Graphics" (JD FOLEY, A.VAN
DAM, Japan Computer Association, 1984) Scanline Algorithm (ibid., Pp. 466-47)
There is 2). This scanline algorithm will be described with reference to FIG. The scanline algorithm roughly consists of three steps:

(1) The closed curve 205 that defines the closed region 200 (FIG. 14A) is divided into minute straight lines that are sufficiently accurate. By this processing, the closed curve 205 is approximated to the polygon 210 (FIG. 14B). (2) The polygon 210 approximated to the closed curve 205 is further scanned by one scanning line (scan line) (that is, one pixel). (FIG. 14 (c)) (3) Apply the individual rectangles 220 along each scan line (FIG. 14 (d)) This scan line algorithm scans It has good compatibility with display devices and printing devices that use lines, and is often used as a method for filling closed areas.

In the execution of this algorithm, the calculation time is the step of approximating the closed region into a polygon, and the calculation time required for this is not directly related to the area of the closed region. For example, even in a closed area having an extremely small area, if the shape is complicated, a great amount of calculation time is required to obtain the approximation accuracy, and the time required for filling is also enormous.

Therefore, an approximate drawing method for solving such a problem has been conventionally developed. One of such approximate drawing methods is as follows.

This method approximates the filling of an elongated closed area in the vertical or horizontal direction.
Specifically, as shown in FIG. 15A, first, the closed region 2
A bounding box 240 that is the smallest rectangle surrounding 30 is determined, and the width and height of the bounding box 240 are compared with a predetermined reference value. Then, when at least one of the width and the height is equal to or less than the reference value, the bounding box 240 is filled (FIG. 15B).
As a result, the closed area 230 is approximated to be filled.

According to this approximate drawing method, when the width of the closed region to be filled is 1 pixel or less or about the same, it is possible to obtain image quality comparable to the scan line algorithm.

It is often the case that a closed region having a thickness of 1 pixel or less is calculated in the calculation, for example, when a precise drawing created by CAD or the like is printed on a small sheet. In the filling processing by the scan line algorithm, even in such a case, since the processing such as the polygon approximation is performed, the drawing processing may require a huge amount of time. On the other hand, if the above-mentioned approximate drawing method is used, the drawing processing time can be saved.

[0011]

However, the above-mentioned conventional approximate drawing method can be applied only when the closed region is elongated in the horizontal direction or the vertical direction, and is sufficient as a means for improving the efficiency of the drawing process. It wasn't very good. That is, the conventional approximate drawing method cannot approximate a slender closed region 250 in an oblique direction as shown in FIG. 16, and in the past, such a closed region must be filled with a scan line algorithm or the like. There wasn't.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a drawing processing apparatus capable of performing an approximation process even for filling a slender closed region which is slender in an oblique direction. .

[0013]

In order to achieve the above-mentioned object, a drawing processing apparatus according to the present invention is a rectangular frame that surrounds a region to be filled and finds a minimum rectangular frame composed of horizontal lines and vertical lines. Calculating means, a diagonal line calculating means for obtaining a diagonal line of the rectangular frame, a region width calculating means for obtaining a maximum width of the region in a direction perpendicular to the diagonal line, and comparing the maximum width with a predetermined reference value, When the maximum width is less than or equal to the reference value, the approximation possibility determination unit that determines that the area can be approximated to be drawn, and when the approximation possibility determination unit determines that the area can be approximated to be drawn, the maximum along the diagonal line An approximate drawing means for drawing a line segment having a width corresponding to a large extent is provided.

In this configuration, a rectangular frame surrounding the area to be filled is obtained, and the filling processing of the area is approximated by the drawing processing of the diagonal line of this rectangular frame. The condition for performing approximate drawing is that the maximum width of the area in the direction perpendicular to the diagonal line of the rectangular frame is equal to or less than a predetermined reference value. For example,
If a value of a width of about 1 pixel is used as a reference value, an area having a thickness of 1 pixel or less is drawn by linear approximation, so that the drawing processing speed is improved. If the reference value is set to a larger value, the target to which the approximation processing is applied becomes wider, so that the drawing processing speed is further improved, but the precision of the drawing result is deteriorated due to the approximation processing. The reference value needs to be determined according to the balance between the quality of the drawing result and the processing speed. It should be noted that in this configuration, the drawing of the line segment is a concept including the filling process of the area corresponding to the line segment.

With this configuration, when the area to be filled is an area that is slender in the oblique direction, the area can be approximated by a straight line (line segment) and drawn.

Further, the present invention encloses the control point group based on the coordinates of the control point group which defines the filling target area,
Rectangular frame calculating means for obtaining a minimum rectangular frame composed of a horizontal line and a vertical line, diagonal line calculating means for obtaining a diagonal line of the rectangular frame, and a distance between the diagonal line and each of the control points,
Region width calculation means for determining the maximum width of the region based on the sum of the maximum values of the distance on each side of the diagonal line, and comparing the maximum width with a predetermined reference value, the maximum width is Approximation propriety determination means for determining that the area is approximate drawable when it is less than or equal to a reference value, and corresponds to the maximum width along the diagonal line when it is determined by the approximation propriety judgment means that approximate drawing is possible. And an approximate drawing means for drawing a line segment having a width.

With this configuration, processing is performed based on the coordinates of the control point group that defines the area to be filled. here,
A control point is a point for defining a closed curve (contour) that encloses a region, and examples are control points of parametric curves such as straight line end points and Bezier curves, nodes of interpolation curves such as spline curves, etc. Is. Graphic data given from a computer to a printer or the like is often expressed in the form of a set of control points. With this configuration, the maximum width of a rectangular frame or area is calculated based on this control point data, and whether or not approximation processing can be performed is determined. By making the determination, the processing speed is increased. In general, the control point is located near the contour of the region, so that the approximation can be accurately determined even if the control point is used.
Even with this configuration, when the area to be filled is an area that is slender in the oblique direction, it can be detected, and the area can be approximated by an oblique straight line (line segment) and drawn.

Further, in this configuration, the area width calculating means performs coordinate conversion so that the diagonal line of the rectangular frame is parallel to one coordinate axis, and the diagonal line and the control point are converted based on the coordinates of each control point after the coordinate conversion. It is also possible to obtain the distance of. In this case, the distance between the diagonal line and the control point can be directly obtained from the coordinate component of the control point, and the maximum width of the area can be easily calculated.

Further, in a preferred aspect of the present invention, the approximate drawing means sets the central axis of the line segment in accordance with a difference between a maximum value of the distance above the diagonal line and a maximum value of the diagonal line below the diagonal line. Shift from the diagonal.

According to this configuration, when the area is biased on either side of the diagonal line, it is possible to draw an approximate line segment at a position that reflects the bias, and the layout relationship of the original area is determined. It is possible to obtain an approximation result that reflects more faithfully.

Further, in another aspect of the present invention, the approximate drawing means sets a line segment having a maximum value of the distance above the diagonal as a line width and a maximum value of the distance below the diagonal to the line width. And the line segment to be drawn are adjacent to each other with the diagonal line as a boundary.

With this configuration, by drawing the line segment having the maximum width of the area on each of the upper side and the lower side of the diagonal line, an approximate drawing result reflecting the bias of the area with respect to the diagonal line as a whole can be obtained. it can.

Further, according to the present invention, the area width calculating means is made to obtain the maximum width for each of the two diagonal lines of the rectangular frame, and when the maximum widths for the two diagonal lines are both smaller than the reference value. And a control means for causing the approximate drawing means to draw a line segment for the diagonal line having the smaller maximum width.

According to this configuration, when approximation can be performed using either of the two diagonal lines of the rectangular frame, the one with the better approximation can be selected and drawn.

Further, the drawing processing apparatus of the present invention is characterized by having reference value input means for receiving a user's input regarding the reference value.

With this configuration, the reference value can be changed for each drawing process, and the user can selectively use the drawing process prioritizing the processing speed and the drawing process prioritizing the precision.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a drawing processing apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a functional block diagram showing the overall configuration of the drawing processing apparatus of this embodiment. The configuration of FIG. 1 has a page description language (PDL: sent from a computer or the like.
This is a device for performing drawing processing based on data of PageDescription Language), and as a concrete example, a printer server or the like which develops page description language data and supplies it to a printer in the subsequent stage corresponds to this.

In FIG. 1, the page description language analysis unit 10
Receives PDL data sent from a computer or the like and analyzes and executes this data. The page description language analysis unit 10 includes an instruction analysis unit 12 and a control instruction execution unit 1.
4 and the drawing command execution unit 16. Instruction analysis unit 12
Analyzes PDL data and distributes each command included in the data to the control command execution unit 14 or the drawing command execution unit 16 according to its type. In the page description language, in addition to drawing commands that instruct drawing of characters and figures, as in general programming languages, control for instructing assignment of variables, numerical operations, control of processing such as repetition and conditional branching, etc. The order is prescribed. For example, the control of the control command designates the paper size and the number of printed sheets. Therefore, the command analysis unit 12 determines the type of each command from the PDL code, classifies and inputs the control command to the control command execution unit 14 and the drawing command to the drawing command execution unit 16.

The control command execution unit 14 holds and manages the data structure, stack, graphic state variables, and the like assumed by the PDL, and according to the control command given from the command analysis unit 12, those state values. , And output those state values according to external reference. In this embodiment, the control command execution unit 14 processes a command that defines a graphic to be drawn. That is, the control command execution unit 14
Extracts the definition information of the figure from the command that defines the figure,
It is organized and maintained in the form of a predetermined data structure and managed.

On the other hand, the drawing command executing unit 16 acquires information necessary for executing the drawing command from the control command executing unit 14, etc., based on the drawing command input from the command analyzing unit 12,
The information is sent to the drawing processing unit 20 in the subsequent stage.

In the drawing processing section 20, the drawing command executing section 16
The drawing process is performed based on the information sent from the device, and the result is written in the drawing buffer 40 which is a bitmap memory. The configuration and functions of the drawing processing unit 20 will be described in more detail later.

As described above, in this embodiment, the part for analyzing the PDL (page description language analysis part 10) and the part for performing the actual drawing process (drawing processing part 20) are configured as separate bodies. As a result, the output of the page description language analysis unit 10 is not limited to the printer, but also to the display device or P
It can be supplied to various devices such as a converter for converting the graphic data described in DL into another data format.
That is, according to this configuration, the page description language analysis unit 1
0 can be used as a general-purpose component for forming various types of drawing processing systems. In the present embodiment, the page description language analysis unit 10 edits and outputs a PDL drawing command in a format conforming to a predetermined specification, and the drawing processing unit 20 following this stage can accept the instruction format. Has become.

Here, PostSc which is a kind of PDL is used.
An example of data described in ript will be shown, and the processing operation of the page description language analysis unit 10 for this will be described. Here, the filling of the closed region 50 shown in FIG. 2 will be described as an example.

The closed region 50 in FIG. 2 is a straight line segment AB, BC,
It is defined as a region surrounded by a closed curve composed of CD and a curved line segment DA. In PostScript, a curve is expressed as a cubic Bezier curve, and a curve segment DA is defined by coordinates of a start point D, an end point A, and control points E and F. The start point and end point of a straight line segment, the start point and end point of a curve segment, and the control point all have the same function in the sense that they define a line segment, so they will all be referred to below uniformly as control points.

FIG. 3 is an example in which the filling processing of the closed region 50 of FIG. 2 is described in PostScript. P
In ostScript, drawing of a graphic is specified by a path that defines the shape of the graphic and the content of drawing operation for the graphic defined by the path. The path is constructed by sequentially adding line segments. The terminal point of the line segment most recently added to the path is called the "current point". The path construction operator is used for path construction. In Figure 3, moveto, lineto, curveto, clos
epath is the path construction operator. The set of numbers in front of these operators indicates the coordinates of the current point. move
to is an operator that specifies a new current point, and is used to indicate the start point of the path. lineto is
It is for adding a straight line segment connecting the old current point and the new current point to the path. cu
rveto is used to add a cubic Bezier curve to the path. closepath is used to explicitly close a path and indicates the process of adding a straight line connecting the current point and the start point of the path to the path. In this way, a series of routes constructed by connecting straight lines and curved lines in order is a path,
This path is treated as abstract shape data that defines lines and areas. Specific drawing processing is realized by causing a paint operator to act on this path.
In Figure 3, fill is the paint operator and this fill
The operator is used to instruct the filling of the closed area enclosed by the paths constructed so far.
In addition to this, the paint operator includes a stroke that draws a line along the path. In this embodiment, the path construction operator is treated as a control command, and the paint operator is treated as a drawing command. In addition, PostScript
For details of t, for example, “PostScript Reference Manual Second Edition” (by Adobe Systems,
Ascii Publishing) is explained in detail.

The data of PostScript as shown in FIG. 3 is in the form of text data in the page description language analysis unit 10.
Entered in. The instruction analysis unit 12 decomposes the text data into integers, names, symbols and the like, and further decomposes the decomposed lexical into data and instructions. The data is the control instruction execution unit 14
Sent to and retained within. Further, it is determined whether the command is a control command or a drawing command, and is input to either the control command executing unit 14 or the drawing command executing unit 16 according to the result. Path building operators such as moveto and lineto are control commands and are sent to the control command execution unit 14. The control command execution unit 14 has a data structure indicating path information, and sequentially adds line segment data obtained by interpreting the path construction operator to the data structure. In the data example of FIG. 3, the path construction operators from moveto to closepath are sequentially sent to the control instruction execution unit 14 in the order of description, and as a result, the data representing the path is constructed in the control instruction execution unit 14. Then, the fill operator is interpreted as a drawing command and is input to the drawing command execution unit 16. A paint operator such as fill needs information of a path to which the processing is applied as an operand. Therefore, the drawing command execution unit 16 issues a reference request for the data of the path constructed up to that time to the control command execution unit 14 as an operand of the fill operator, and the path obtained in accordance with the request is issued. Information and type of drawing command itself (fill in this case)
And outputs the drawing instruction data to the drawing processing unit 20 in the subsequent stage.

FIG. 4 shows the data structure of the drawing instruction data supplied from the drawing command execution unit 16 to the drawing processing unit 20, and corresponds to the PostScript description of FIG. In FIG. 4, in the command type 102, an identifier (fill in this example) indicating the type of drawing command is described. Following the instruction type 102, data 104 indicating the length of the operand of the drawing instruction is described. Since the path data changes depending on the number of line segments that make up the path, the drawing instruction operand is variable length data. Therefore, the drawing processing unit 2
For processing 0, data 104 indicating the size of the operand
Is required. Then, the operand 106 follows the data 104. In this example, operand 106
Is an array of line segment data defining a closed region.
Each element of this array has an identifier 108 and an identifier 2 respectively.
It is composed of fields of one numerical data 110. The data 104 indicates the number of elements in this array.
The numerical data 110 indicates the coordinates of points on the drawing area. The identifier 108 indicates the meaning of the point and corresponds to the PostScript path construction operator. move indicates a process of moving to a specified point without drawing a line, and corresponds to moveto of PostScript. line indicates the process of moving while drawing a straight line from the point of the immediately preceding element to the specified point, and corresponds to lineto. Also, in this example, PostScript
The curveto operator is 3 for curve1, curve2 and curve3
It is divided into two elements. curve1 and curve2 are Bezier 3
Two control points of the cubic curve are shown, and curve3 shows the end point of the Bezier cubic curve. With these three elements, the point of the element immediately before curve1 is the start point, the point specified in curve3 is the end point,
A Bezier cubic curve with the points specified by curve1 and curve2 as control points is specified. And close is closepath
It corresponds to, and shows the processing of moving from the point of the previous element to the start point of the path (that is, the point indicated by move) while drawing a straight line and explicitly closing the path. This element completes the path of the closed curve. Note that in this example, curv
With e1 to curve3, the path has already reached the start point, so this close does not draw a line, and clos
e only serves as an explicit declaration that the path is a closed curve.

As described above, in this embodiment, when the page description language analysis unit 10 detects a paint operator, the page description language analysis unit 10 draws the operator and the operand indicating the target path in the format shown in FIG. The instruction data is edited and output to the drawing processing unit 20.

In FIG. 4, the case where the fill operator is given as a drawing command has been described, but the page description language analysis unit 10 similarly creates and outputs drawing instruction data for the stroke operator that draws a line. To do. Also,
For the operator who instructs the printing of the character string, the drawing instruction data having the character string as an operand is created and output. Further, the showpage operator described after the fill operator in FIG. 3 is an operator for instructing the display (printing) output of the drawing result formed so far, and is treated as a drawing command. The drawing command execution unit 16
Page that shows output instruction of drawing result when showpage is received
The data including the eject identifier is output to the drawing processing unit 20. An integer value indicating the number of printed sheets is added to this pageeject identifier. The number of printed sheets is set in the control command execution unit 14 based on the numerical value attached to the showpage operator, and the default value is 1. The drawing command execution unit 16 reads out the print number data from the control command execution unit 14, adds it to the pageeject identifier, and outputs it. As described above, when the drawing command executing unit 16 receives the drawing command from the command analyzing unit 12, the drawing command executing unit 16 obtains the identifier of the drawing command corresponding to this command, and further obtains the information of the operand necessary for executing this command from the control command executing unit. 14 and the like, drawing instruction data having an identifier at the head is created from these, and the drawing instruction data is transferred to the drawing processing unit 20.

Next, the drawing processing section 20 will be described.
The drawing processing unit 20 is configured to perform drawing processing on the drawing buffer 40 based on the drawing instruction data sent from the page description language analysis unit 10 described above. Processor 24, line segment processor 2
6, area processing unit 28, curve drawing unit 30, straight line drawing unit 3
2. Includes a scan converter 34. Drawing instruction detection unit 22
Analyzes the drawing instruction data received from the page description language analysis unit 10 to obtain the type of instruction, and allocates each drawing instruction data to an appropriate processing unit according to the type. The type of instruction is determined by the identifier shown at the beginning of the drawing instruction data. As a result, a character string print instruction is given to the character string print processing unit 24, and a line segment drawing instruction is given to the line segment processing unit 26.
The instruction to fill the closed area is distributed to the area processing unit 28. For example, the drawing instruction data of the identifier fill is sent to the area processing unit 28.

The character string print processing unit 24 writes the character string data included in the drawing instruction data into the drawing buffer 40 in the designated font. As the drawing buffer 40, for example, a memory that holds a black and white two-tone bitmap image having a resolution of 72 dpi (72 dots per inch) can be used.

The line segment processing section 26 is a specialized module for processing a line segment drawing instruction. The line segment processing unit 26 analyzes the data of the path included in the drawing instruction data, decomposes the path into the straight line segments and the curved line segments of the constituent elements, and the straight line segments are converted into the straight line drawing unit 32 and the curved line segments. On the other hand, the curve drawing unit 30
To each drawing instruction. The straight line drawing unit 32 draws the drawing buffer 40 according to the given start point and end point data.
Draw a straight line on top. In addition, the curve drawing unit 30 draws a curve on the drawing buffer 40 in accordance with the given start point, control point, and end point data.

The area processing unit 28 is a module for processing the filling of the closed area. A line drawing unit 32 and a scan conversion unit 34 are connected to the area processing unit 28. Here, the scan conversion unit 34 is a module that draws a filled figure on the drawing buffer 40 using the scan line algorithm described above. Area processing unit 2
8 analyzes the data of the closed area (path) included in the drawing instruction data, and determines whether or not the closed area can be approximated by a straight line segment. If linear approximation is not possible, the area processing unit 28
Supplies the data of the closed region to the scan conversion unit 34, and causes the scan conversion unit 34 to execute the filling process. On the other hand, when straight line approximation is possible, the area processing unit 28 creates approximate straight line data and supplies it to the straight line drawing unit 32, and causes the straight line drawing unit 32 to draw straight line segments. The processing such as the approximation possibility determination by the area processing unit 28 will be described in detail later.

Note that the drawing instruction data given from the page description language analysis unit 10 to the drawing processing unit 20 may be something like page eject that does not involve an operation on the drawing buffer 40. When pageeject is input as the drawing instruction data, the drawing instruction detection unit 22 sends the code indicating the end of the drawing process and the data of the number of prints to the device such as a printer connected in the subsequent stage via the signal line 36. Send notifications containing. The device at the latter stage receiving this notification is the drawing buffer 4
The drawing result is read from 0 and processing such as printing is performed.

The overall image of the processing flow in the apparatus of FIG. 1 has been described above. Next, the processing of the area processing unit 28 will be described in more detail.

As described above, the area processing unit 28 first determines whether or not the filling processing of the closed area can be approximated by drawing a straight line segment. In the present embodiment, a straight line having a line width that encloses a closed region is assumed, and when the line width of the straight line is equal to or less than a predetermined reference value, it is determined that the line can be approximated, and the approximate drawing process is executed. This approximation process is divided into the following three stages.

The first step is the given closed region (pass).
Is a step of determining whether or not the data of 1 is a continuous area. A closed area (path) that is the target of one filling instruction (for example, fill) may be composed of a plurality of closed areas that are not continuous. In such a case, the plurality of closed areas that are not continuous are combined into one continuous area. If approximated by the straight line segment, the impression of the drawing result may be quite different from the original figure. Therefore, in the present embodiment, the approximation process is performed only when the closed region to be filled is one continuous region. FIG. 5 shows the procedure of this first-stage determination process. Area processing unit 28
Is the operand 106 (see FIG. 4) of the drawing instruction data, the first entry is mo
It is checked whether it is ve (S10), and then the last entry is cl
It is checked whether it is ose (S12). If one of these determination results is no, the area processing unit 28 determines that this cannot be approximated, and sends the data of this closed area to the scan conversion unit 34 (S16). Then, it is checked whether there is move or close in the entries other than the first and last entries (S
14). If the result of this determination is yes, it means that the closed area (path) to be filled is divided into a plurality of closed areas (sub-paths), so the area processing unit 28 determines that this cannot be approximated, and The data of the closed region is sent to the scan conversion unit 34 (S16). Then, only when the result of the determination in S14 is no, that is, when the entry of the closed area is move, the end is close, and there is no move or close in the other entries, the following second stage Go to judgment.

In this second step, it is judged whether or not the closed region to be filled can be approximated by a straight line in the horizontal or vertical direction, and if this can be approximated, instead of filling the closed region, an approximate straight line is drawn. Draw minutes. Numerical calculations are required after the second stage. In the area processing unit 28,
Variables and the like used in these arithmetic processes are collectively managed as a structure named "data" shown in FIG.

Here, each member of the structure "data" will be described. First, the real number "limit" is a reference value used for determining whether or not linear approximation is possible, and indicates the maximum value of the line width that can be approximated. Next, in the structure “bb”, the data of the bounding box that surrounds the closed area is set. For the bounding box, (xmin, ymin) is the lower left vertex, (xm
ax, ymax) is defined as a rectangle parallel to the coordinate axis with the upper right vertex. The value of the diagonal of the bounding box is set to the real number "dd". This value is used in the determination in the next third stage. The coordinates of the start point and the end point of the approximate straight line segment are set in the structures "p0" and "p1", respectively. Then, in "linewidth", the line width of the approximate straight line segment when the closed region is linearly approximated is set.

The procedure of the second stage processing will be described with reference to FIG. First, in S20, the limit in the structure data
Then, the reference value for the judgment is set. This reference value is a default value registered in advance in the system. In FIG. 7 and the like, expressions such as “data.limit” are used, but this is in the form of “structure.member name” and indicates a reference to a member in the structure.

Next, in S22, a bounding box surrounding the closed area to be filled is obtained. In this embodiment, a bounding box is a minimum rectangular frame that surrounds a control point group (including the start point and the end point of a line segment) that defines a closed region and that is parallel to the coordinate system. Specifically, x of each control point
Maximum value xmax and minimum value xmin of coordinates and maximum value ym of y coordinate
The ax and the minimum value ymin are obtained, and those values are set as the members of the structure bb. The coordinates of each control point can be obtained from the numerical data 110 of the operand 106 of the drawing instruction data (see FIG. 4). As a result, a rectangular frame, that is, a bounding box, in which the point (xmin, ymin) is the lower left vertex and the point (xmax, ymax) is the upper right vertex, is defined. As described above, in the present embodiment, the bounding box can be determined only by obtaining the maximum value and the minimum value of the coordinates of the control points, and the processing can be performed at extremely high speed.

The Bezier curve has the property that the curve is included in the convex polygon formed by connecting the control points (including the start point and the end point of the curve) (convex closure property). , Considering the bounding box that surrounds the convex polygon, the curve is completely contained in the bounding box. Therefore, in the case where a closed region is defined by a combination of a straight line and a Bezier curve like PostScript, if the bounding box surrounding the control points of the straight line and the curve is obtained, the entire closed region is the bounding box. Will be completely contained within. In this case, the resulting bounding box is the true bounding box (ie, it encloses a closed region,
The smallest bounding box parallel to the coordinate system) does not necessarily match, but is never smaller than the true bounding box. Therefore, in this example, S24 and S, which will be described next,
In the approximation propriety determination in 26, if a true bounding box is used, a closed region that is determined to be linearly approximated may be determined to be not approximated, but a closed region that should not be linearly approximated (that is, from a reference value (A large closed area)
There is no problem in practical use because it is not determined that can be approximated. Of course, if the processing capacity and the processing speed of the apparatus are sufficient, the true bounding box of the closed region may be obtained and the processing may be performed based on this.

When the bounding box is obtained, the width of the bounding box, that is, the length of the side in the x direction (xmax-xmin) is determined in S24, and this is used as a reference value.
Compare with limit. As a result of the comparison, when the length of the side in the x direction is equal to or smaller than the reference value, the closed region can be regarded as an elongated region whose width extending in the y direction is equal to or smaller than the reference value.
Therefore, in S26, the closed region is approximated to the straight line segment corresponding to the bounding box. For more details,
In the structure data, first set (xmax + xmin) / 2 for the x-coordinates of p0 and p1, set ymin and ymax for the y-coordinates of p0 and p1, respectively, and set the linewidth in the x-direction of the bounding box. Width of (xmax−xmi
n) is set. By drawing straight lines with p0 and p1 as the start and end points and linewidth as the line width, the processing result equivalent to filling the bounding box can be obtained. After setting the data for the structure data in S26, the area processing unit 28 issues an instruction to the straight line drawing unit 32 to draw a straight line having a line width linewidth from the point p0 to the point p1 (S32). The straight line drawing unit 32 draws the designated straight line in the drawing buffer 40.

If the result of the determination in S24 is no, S
At 28, the height of the bounding box, that is, the length of the side in the y direction (ymax-ymin) is obtained, and this is used as the reference value limi
Compare with t. As a result of this comparison, when the length of the side in the y direction is equal to or less than the reference value, the closed region can be regarded as an elongated region having a width extending in the x direction equal to or less than the reference value, and it is determined that linear approximation is possible. It Therefore, in this case, the parameter representing the approximate straight line segment is set in the structure data in S30, and S
At 32, these parameters are transmitted to the straight line drawing unit 32. As a result, the line drawing unit 32 causes the drawing buffer 40 to
Draw the approximate straight line segment on.

If the result of the determination in S28 is no,
That is, when both the width and height of the bounding box are larger than the reference value limit, the process proceeds to the next third step.

In the process of the third stage, it is determined whether or not the closed area to be filled can be approximated by the diagonal line of the bounding box. The procedure of this third stage processing is shown in FIGS. 8 and 9. In the present embodiment, it is considered that the closed region is approximated by the minimum straight line segment that covers the closed region and extends along the diagonal line. Whether or not the approximation can be performed basically depends on whether the maximum width of the closed region in the direction perpendicular to the diagonal line is larger or smaller than the reference value.The maximum width of the closed region is the diagonal line of the bounding box. It can be regarded as the line width of an approximate straight line when approximated. Therefore, in the present embodiment, the line width of the approximate straight line segment is trial-calculated, this line width is compared with the reference value, and when this line width is smaller than the reference value, it is determined that approximation is possible. In the present embodiment, in order to realize high-speed processing, not the actual closed curve that defines the closed region,
The maximum width of the closed region (that is, the line width of the approximate straight line segment) is obtained based on the control points that define the closed curve. Hereinafter, the processing procedure of the third stage will be described in detail by taking the closed region 66 shown in FIG. 10 as an example with reference to the flowcharts of FIGS. 8 and 9.

The closed region 66 in FIG. 10 is a Bezier cubic curve 6
The area surrounded by 2 and 64, the curve 62 is the control point 6
0-1, 60-2, 60-3, 60-4, and the curve 64 is the control points 60-4, 60-5, 60-6, 60-.
It is defined in 1. A bounding box 70 has already been obtained for the closed region 66 in the second step S22 (see FIG. 11).

In this embodiment, first, one of the two diagonal lines of the bounding box 70 is selected and the possibility of approximation by this diagonal line is examined. In this embodiment, the diagonal line 72 having a positive inclination is first selected. In order to determine the approximation possibility, it is necessary to obtain the line width of the approximation straight line segment as described above. In the present embodiment, the distance between the diagonal line 72 and each control point is obtained, and the diagonal line 72 of those distance values is calculated.
The maximum value of the control points on the upper side of and the maximum value of the control points on the lower side of the diagonal line 72 are obtained, and the sum of the maximum values on both sides thereof is set as the line width of the approximate straight line segment. However, if the distance between the diagonal line and the control point is calculated according to the definition of the distance between the point and the straight line, the number of square operations increases and the calculation process takes time. Therefore, in the present embodiment, the calculation process is performed by the following method. The amount has been reduced.

That is, in this method, as shown in FIG. 11, a straight line that passes through each control point 60 and is parallel to the diagonal line 72 is obtained, the y-intercept ydi of the straight line is obtained, and the maximum value of these ydi is obtained.
The line width of the approximate straight line segment is obtained by projecting the difference between ydmax and the minimum value ydmin in the direction perpendicular to the diagonal line.

First, the slope dd of the diagonal line 72 can be obtained by the following equation.

[0062]

## EQU00001 ## dd = (ymax-ymin) / (xmax-xmin) (1) Each coordinate value on the left side is set in the bounding box bb in the structure data.

Next, the coordinates (px, py) of the control point and the inclination
Based on dd, a y-intercept ydi of a straight line passing through the control point i and parallel to the diagonal line is obtained. This is obtained by the following formula, which is a modification of the straight line formula.

[0064]

(2) ydi = py-px * dd (2) This operation is performed for all control points to find the maximum and minimum values of ydi, and set those values as ydmax and ydmin, respectively.

Here, the line width linewidth of the approximate straight line segment is
The following relational expression is satisfied.

[0066]

[Equation 3] linewidth = (ydmax-ydmin) * sin φ = (ydmax-ydmin) * cos θ (3) On the other hand, a right angle consisting of points (0,0), (1,0), (1, dd) Considering the Pythagorean theorem for a triangle, the following relation holds.

[0067]

## EQU4 ## 1 / (cos θ) ² = 1 ² + dd ² (4) When this equation (4) is transformed,

(5) (cos θ) ² = 1 / (1 + dd ² ) ... (5) is obtained. From this equation and equation (3),

[Equation 6] linewidth ² = (ydmax-ydmin) ² / (1 + dd ² ) ... (6) The relational expression is derived. The line width linewidth of the approximate straight line segment can be obtained by taking the square root of the calculation result of the equation (6).

In order to realize the above processing, the area processing unit 28 uses ydmax and ydmin as temporary variables in addition to the structure data shown in FIG. In step S40, the temporary variable ydmax is initialized to the minimum integer value handled by the system, and ydmin is initialized to the maximum integer value handled by the system. Then, in S40, the inclination of the diagonal line 72 is further calculated based on the above equation (1), and this is set in the member dd of the structure data. Next, in S42, one control point in the closed region is taken out from the operand of the drawing instruction data, and its x coordinate and y coordinate are substituted into temporary variables px and py. Then, in S44, the y-intercept of a straight line passing through the control point and parallel to the diagonal line is obtained based on the above equation (2), and the larger of the obtained y-intercept value and ydmax up to that time is newly added. Ydmax, and similarly, the smaller of the y-intercept value and the ydmin up to that point is set as the new ydmin.
Then, the operations of S42 and S44 are repeated for all the control points included in the drawing instruction data. When it is determined in S46 that all control points have been processed, the temporary variables ydmax and ydmin are the maximum value and the minimum value of the y-intercept, respectively.

When the maximum value and the minimum value of the y-intercept are obtained in this way, next, in S48, the square of the line width squared of the approximate straight line segment is calculated according to the above equation (6). The trial calculation result is temporarily stored in the member linewidth of the structure data.

Whether the linear approximation is possible or not is determined by the square value of the line width. That is, in S50, the square of the line width, that is, the current value of the linewidth of the structure data is compared with the square of the reference value limit that is also registered in the structure data, and linear approximation is possible when the linewidth is less than or equal to the square of limit. To determine.

As described above, in this embodiment, not the actual contour of the closed region itself but the line width of the approximate straight line segment is obtained from the control point that defines the contour, and the determination as to whether or not the approximation is possible is performed based on this. However, even with such processing, it is possible to determine whether or not the approximation can be performed with sufficient accuracy in practical use. In particular, PostScr
When the closed region is defined by a straight line and a Bezier curve like ipt, the closed region is included in the approximate straight line obtained from the control points due to the convex closure property of the Bezier curve. On the other hand, since the width of the closed region itself is definitely smaller than the line width of the approximate straight line, in the present embodiment, there is no case in which it is determined that a closed region having a width larger than the reference value can be approximated, and there is no practical problem. . Of course, if the processing capacity and the processing speed of the apparatus are sufficient, the maximum width of the closed region may be obtained based on the contour of the closed region itself, and the approximation may be determined based on this.

When it is determined in S50 that the straight line can be approximated, the line width of the approximate straight line segment and the coordinates of the start point and the end point are obtained (S52). Specifically, first, the square root of linewidth is newly set to the linewidth of the structure data, and this is set as the linewidth of the approximate straight line segment. Then, the end point of the diagonal line 72 (xm
in, ymin) and (xmax, ymax) are the points p0 and
Set as coordinates of p1. And the structure at S52
When the data setting for data is completed, the area processing unit 28
Is the line width li from the point p0 to the point p1 for the straight line drawing unit 32.
It gives an instruction to draw a newidth line (S54). As a result, the line drawing unit 32 draws the specified line in the drawing buffer 40. FIG. 12 shows an approximate straight line segment 80 obtained for the closed region 66 shown in FIG.

The examples of FIGS. 10 to 12 are the cases where it is determined in S50 that linear approximation is possible, that is, the diagonal lines of the bounding box that can be approximated with a positive inclination. On the other hand, if it is determined in S50 that linear approximation is not possible, the possibility of approximation for the other diagonal line of the bounding box is checked. This procedure is shown in FIG.

In the processing procedure of FIG. 9, first, in S60, the slope dd in the structure data is set to a value obtained by multiplying the value of dd up to that time by -1. The subsequent processing is basically the same as in the case of FIG. That is, ydmax and ydmin are obtained by the same processing as in the case of FIG. 8 (S62 to S66), the square value of the line width of the approximate straight line segment is further obtained (S68), and this is compared with the square value of the reference value limit. , It is determined whether or not linear approximation is possible (S70). Then, when it is determined that the straight line can be approximated, the square root of the square value of the line width is obtained to obtain the line width limitwidth of the approximate line segment, and further the end points of the diagonal line (xmin, ymax)
And (xmax, ymin) are set as the coordinate values of the start point p0 and the end point p1 of the approximate straight line segment, respectively (S72). And
The line width, the start point and the end point data are given to the straight line drawing unit 32 to draw an approximate straight line on the drawing buffer 40 (S).
74). If it is determined in S70 that the closed region cannot be approximated, it means that the closed region cannot be approximated by the diagonal line of the bounding box. Therefore, the control point data of the closed region is directly input to the scan conversion unit 34. The image data is supplied and the scan conversion unit 34 is caused to execute the area filling processing by the scan line algorithm (S76).

As described above, in the present embodiment, first, the approximation by the bounding box itself is tried, and when this is impossible, the approximation by the diagonal line of the bounding box is tried. According to this method, not only when the closed region to be filled is elongated in the vertical and horizontal directions (that is, the width is smaller than a predetermined reference value), but also when it is elongated in the oblique direction, the filling process of the closed region is performed. Can be approximated by a straight line drawing process.

In the example described above, when it is determined that approximation is possible, the straight line drawing unit 32 draws a straight line segment. However, the present embodiment is not limited to this. For example, a polygon corresponding to an approximate straight line segment may be drawn. It is also possible to obtain an area and send the data of this area to the scan conversion unit 34 to perform the filling processing. Even with such processing, the filling processing of the closed area can be approximated at high speed. However, in general, the straight line drawing processing by the straight line drawing unit 32 is more preferable than the scan conversion unit 3.
Since the area filling processing can be performed at a higher speed than the area filling processing by 4, the former can obtain a more preferable result for the purpose of speeding up the processing.

It is also possible to carry out the trial calculation of the line width of the approximated straight line in the third stage after the coordinates of each control point are converted into a coordinate system convenient for distance calculation. In this case, after the diagonal line of the bounding box is obtained, the coordinates of each control point are coordinate-converted (that is, rotated) so that the diagonal line becomes parallel to the x-axis (or the y-axis). By doing so, the line width of the approximate straight line can be obtained only by simply comparing the coordinate components.

In the above embodiment, the reference value limit of the approximation judgment is assumed to be about one pixel width of the drawing processing apparatus. However, the reference value limit may be set to a larger value. If so, the drawing process can be further speeded up. When the reference value limit is set to a value larger than the width of one pixel, the image quality can be improved by the following method.

That is, according to this method, when the distribution of the closed region is not uniform with respect to the diagonal of the bounding box and is biased to one side, an approximate straight line segment reflecting the bias is drawn. To this end, as shown in FIG. 13, the midpoint (ydmax + ydmin) / 2 of the maximum value ydmax and the minimum value ydmin of the y-intercept line of the straight line that passes through the control point 60 and is parallel to the diagonal line 72 is calculated, and the approximate straight line segment is obtained. Diagonal line 7 passing through this midpoint
Shift to a straight line 74 parallel to 2. The start point p0 and the end point p1 (see FIG. 13) of this approximate straight line segment are obtained by a simple calculation. In the example of FIG. 13, the approximate straight line segment is shifted in the direction perpendicular to the diagonal line, but it may be shifted in the y-axis direction.

The following method is also conceivable as a method of approximate drawing that reflects the bias of the closed region with respect to the diagonal line. That is, in this method, the closed region is considered separately on the upper side and the lower side of the diagonal line of the bounding box, and the maximum value of the distance from the diagonal line of the control point is first obtained for each side. This maximum value can be obtained by the method using the aforementioned y-intercept. Then, with respect to the upper side and the lower side of the diagonal line, the maximum value on each side is set as the line width, and two straight lines adjacent to each other on the diagonal line are drawn. Also with this method, the same result as the method of shifting the central axis of the approximate straight line according to the bias of the closed region can be obtained.

Further, in the above embodiment, when it is determined that one diagonal line can be approximated, the diagonal line is immediately used for approximation. However, in order to improve the accuracy of the approximation result, both diagonal lines can be used. It is also possible to take a method of examining the approximation possibility with respect to and selecting the one that can obtain a better approximation straight line segment. In this case, the line widths of the approximate straight line segments are obtained for both diagonal lines of the bounding box, the diagonal line with the smaller line width is selected, and the approximate straight line segments are drawn along this diagonal line.

Further, in the above embodiment, the reference value limit of the approximation judgment is a fixed value registered in advance in the system, but the value of the reference value limit can be dynamically changed. That is, the value of the reference value limit needs to be fixed by the time the approximation determination process is started. Therefore, a user interface for inputting the reference value is provided in the system, and the user sets the reference value for each drawing processing opportunity. It can also be configured to input. With this configuration, the user can set an appropriate reference value in consideration of the trade-off between the processing speed and the drawing quality.

In the above embodiment, the case where the closed area to be drawn is described in PDL has been described.
The present invention is not limited to such a case, and can be applied to the filling processing of areas expressed in various formats.

[0084]

As described above, according to the present invention,
When the area to be filled is slender in the diagonal direction, by drawing a diagonal line of a rectangular frame surrounding the area, the filling of the area can be processed approximately at high speed.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a schematic configuration of a drawing processing apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a closed region.

3 is a Pos for instructing filling of a closed area in FIG.
It is a description example of tScript.

FIG. 4 is a diagram showing the content of drawing instruction data created by a page description language analysis unit of the embodiment corresponding to the description of FIG.

FIG. 5 is a flowchart showing a processing procedure of a first step of determining whether or not approximation processing is possible.

FIG. 6 is a diagram showing a structure of data used in the area processing unit of the embodiment.

FIG. 7 is a flowchart showing a processing procedure of a second step of determining whether or not approximation processing is possible.

FIG. 8 is a flowchart showing a part of a processing procedure of a third step of determining whether or not approximation processing is possible.

FIG. 9 is a flowchart showing the remaining part of the processing procedure of the third step of determining whether or not approximation processing is possible.

FIG. 10 is a diagram showing an example of a closed region elongated in an oblique direction.

FIG. 11 is a diagram for explaining the procedure of an approximation process for the closed region in FIG.

FIG. 12 is a diagram showing a result of approximate drawing of the closed region in FIG. 10 by a straight line segment in an oblique direction.

FIG. 13 is a diagram for explaining a modified example of the approximate drawing method.

FIG. 14 is a diagram for explaining a procedure of a scanline algorithm.

FIG. 15 is a diagram for explaining a conventional approximate drawing method.

FIG. 16 is an example of a region elongated in an oblique direction.

[Explanation of symbols]

10 page description language analysis unit, 12 instruction analysis unit, 14
Control command executing unit, 16 drawing command executing unit, 20 drawing processing unit, 22 drawing instruction detecting unit, 24 character string printing processing unit, 26 line segment processing unit, 28 area processing unit, 30 curve drawing unit, 32 straight line drawing unit, 34 scan converter, 40
Drawing buffer.

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G06T 11/40 200 G09G 5/20 G09G 5/36

Claims (7)

(57) [Claims] 1. A rectangular frame calculation unit that surrounds a region to be filled and that calculates a minimum rectangular frame that is composed of horizontal lines and vertical lines, a diagonal line calculation unit that calculates a diagonal line of the rectangular frame, and a direction perpendicular to the diagonal line. Region width calculation means for obtaining the maximum width of the region, and comparing the maximum width with a predetermined reference value, and if the maximum width is less than or equal to the reference value, the region is approximated to be drawable approximation A possibility determining unit, and an approximate drawing unit that draws a line segment having a width corresponding to the maximum width along the diagonal line when the approximate possibility determining unit determines that approximate drawing is possible. Drawing processing device. 2. A rectangular frame calculating means for calculating a minimum rectangular frame that surrounds the control point group and is composed of horizontal lines and vertical lines based on the coordinates of the control point group that defines the area to be filled, Diagonal line calculating means for obtaining a diagonal line, the distance between the diagonal line and each of the control points is obtained, and the area width for determining the maximum width of the area based on the sum of the maximum values of the distances on each side of the diagonal line. Computation means, comparing the maximum width with a predetermined reference value, the approximation possibility determination means for determining that the region can be approximated when the maximum width is less than the reference value, the approximation possibility determination means Approximate drawing means for drawing a line segment having a width corresponding to the maximum width along the diagonal line when it is determined that approximate drawing is possible. 3. The drawing processing apparatus according to claim 2, wherein the area width calculation means performs coordinate conversion so that the diagonal line is parallel to one coordinate axis, and based on the coordinates of each control point after the coordinate conversion. A drawing processing apparatus for obtaining the distance. 4. The drawing processing device according to claim 2 or 3, wherein the approximate drawing unit is configured to, in accordance with a difference between a maximum value of an upper side and a maximum value of a lower side of the diagonal of the distance,
A drawing processing apparatus, wherein a central axis of the line segment is shifted from the diagonal line. 5. The drawing processing apparatus according to claim 2, wherein the approximate drawing unit is configured to divide a line segment having a maximum value of the distance above the diagonal line as a line width and the distance below the diagonal line. A drawing processing apparatus, which draws a line segment having a maximum value as a line width adjacent to each other with the diagonal line as a boundary. 6. The drawing processing apparatus according to claim 1, further comprising causing the area width calculating unit to obtain the maximum width for each of two diagonal lines of the rectangular frame. When both of the maximum widths are smaller than the reference value, the drawing processing apparatus further comprises control means for causing the approximate drawing means to draw a line segment for a diagonal line having a smaller maximum width. 7. The drawing processing apparatus according to claim 1, further comprising a reference value input unit that receives a user's input regarding the reference value.