JPH0634237B2 - Image clipping method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention optically scans a drawn figure by an image scanner to define it as run-length data, and further executes a figure conversion operation. The present invention relates to an image clipping method for clipping a rectangular area of a part.

[Conventional technology]

First, the run length vector that is generally used in the image processing technique will be described. FIG. 4 is a diagram showing the run-length vector of the figure “A” drawn on the paper. In the figure, 1 is a white background to be read, 2 is a figure drawn in black in FIG. A locus of scan, 4 is a run length vector indicating from which start point to end point the black of the figure 2 is continuous in the scan, 5 is the start point of the run length vector 4, 6 is the end point of the run length vector, X, Y is a coordinate axis.

Here, the scanning is performed on the X-axis at regular intervals to obtain run-length data for the entire drawing.

Next, a run length vector data calculation algorithm in the conventional figure conversion method will be described below.
The equation (1) is a conversion equation applied when correcting the distortion of the figure, and a to h are constants.

Here, x and y in the equation (1) represent the start point or the end point of the run length vector and are coordinate values on the X and Y axes,
x ′ and y ′ are coordinate values of points on the X and Y axes after conversion corresponding to the coordinate value (x, y).

Parameters a, b, c, d, e, f, g, and h are coordinates (x ₁ , y ₁ ) and (x ₂ , y ₂ ) of four points in the scan data on the input diagram as shown in FIG. , (X ₃ , y ₃ ),
(X ₄ , y ₄ ) and the coordinates (x ₁ ′, y ₁ ′), (x ₂ ′, y ₂ ′), (x ₃ ′, on the output diagram corresponding to the four points,
It is obtained by solving the equation (2) from y ₃ ′) and (x ₄ ′, y ₄ ′).

In this case, the coordinates of the four points in the scan data on the input diagram and the coordinates on the output diagram corresponding to the four points are displayed by displaying the scan data on a display screen by a data input means as is well known. It is obtained by the instruction of the operator who sees the screen. An example of this instruction method is shown in FIG. FIG. 6 (a) is an example of a screen display of scan data, and the shaded area is an area display of the result of pointing at four points using a stylus pen.

After the calculation of equation (1), the coordinate value x ′ (or y ′) of the start point / end point is obtained even if the run length data is in the same scan.
Are generally not equal.

For clipping a part of the rectangular area of the run-length vector data after the calculation of the equation (1) as shown in FIGS. 6 (a) to 6 (b), conventionally, for example, "PC CAD
"Practical use" (Technical Review, August 1984), page 26-
The following procedure, shown on page 28, was used.

As shown in FIG. 7, the space is divided into 9 parts in the clipping region and outside the range, and 4 bits are encoded as shown in FIG. If these 4 bits are the 1st, 2nd, 3rd and 4th bits from the left, the fact that the 1st bit is 1 means that it is above the upper edge limit of the clipping region, and that the 2nd bit is 1 means that clipping It is below the edge lower limit of the area, the third bit being 1 means to the right of the edge right limit of the clipping area, and the fourth bit being 1 means the edge left edge of the clipping area. Means more to the left.

Next, which space each of the start point and the end point of the vector falls into is classified, and the logical product of each 4-bit code is taken.
If the result is not 0000, it is completely outside the vector and clipping area, and there is no need to draw at all.

When the logical product of the above 4-bit codes is 0000, 1 of each 4-bit code of the start point and end point of the vector
The vector is cut according to the meaning of the bit.

For example, as shown in FIG. 8, in the vector AB, AC is first cut out to become the vector CB, then CD is cut out, and finally the vector DB is obtained, and the vector in the clipping area is obtained.

Further, in the flowcharts of FIGS. 9- (1) and (2), 7 is a “correction constant calculation” step, 8 is a “scan row counter initial setting” step, 9 is a “scan row end point” determination step, and 10 is a "Run end length within scan" determination step, 11 "calculation of equation (1)" step, 12 "scan row count up" step, 13 "start point x'direction classification" step, 14 "start point y"'Directionclassification' step, 15'end point x'direction classification 'step, 16'end point y'direction classification' step,
17 is a spatial code logical product step, 18 is a logical product judgment step, 19 is a vector equation calculation step, 20 is a bit counter initial setting step, 21 is a start point code bit judgment step, 22 Is the step of “calculating the intersection of two straight lines and cutting out unnecessary vectors”, and 23 is “bi
"Count up counter value" step, 24 is "4bit
"End" determination step, 25 is "bit counter initial setting" step, 26 is "end point code bit determination" step, 27 is "two straight line intersection calculation, unnecessary vector cutout" step, 28 is "bit count value count up" Step, 29 is a step of judging "4bit end",
30 is a "vector drawing" step.

Furthermore, FIG. 10 shows a configuration example of a general image processing system (for example, an image information file device). That is,
(A) is an image input / output device, which is connected to an image processing device (D) through an image bus (C) together with the image memory device of (B).

(E) is a registration search processing device, which is a data processor, C
It is composed of an RT, a keyboard and the like, and is connected to an index management device (G) such as a floppy disk or a magnetic disk via a data bus (F) to perform a predetermined calculation.

Next, the operation of FIG. 9- (1) and (2) will be described.
First, in step 7 “calculation of correction constant”, the parameters a, b, c, d, e, f, g and h of the equation (1) are calculated,
After performing the initial setting of the target scan line in the “scan line counter initial setting” of step 8, step 9
If there is no scan line of interest in the "scan line end" determination, the operation is ended, and if there is a scan line of interest, the process proceeds to step 10.

If it is determined in step 10 that "run length within scan" is complete, and there is no run length data for which conversion operation has not been performed in the target scan row, "scan row count up" in step 12 If it exists, the process proceeds to “Operation of Expression (1)” in step 11. Then, in step 11, "calculation of equation (1)" is performed on the coordinate values of the start point and the end point of the run length vector to obtain the coordinate value of the corresponding run length vector.

After "calculation of equation (1)" in step 11, step 13
"Starting point x'direction classification", Step 14 "Starting point y'direction classification", Step 15 "Ending point x'direction classification", Step 16 "Ending point y'direction classification". The 9-division space of FIG. 7 is classified for each.

Next, in "spatial code AND" of step 17, the logical product of the spatial classification code at the start point of the vector and the spatial classification code at the end point of the vector is calculated. Then, in the "logical product determination" of step 18, if the logical product is 0000, the process branches to step 19, and if there is no 0000, the vector is not in the clipping region, so the process returns to step 10.

In "calculation of vector equations" in step 19, an equation of a straight line passing through the starting point of the vector is obtained. In the "bit counter initial setting" of step 20, the counter for counting the bits of the spatial code 4 bits is initialized, and step 2
"Count up the bit counter value" in step 3 and step 24
According to the determination of "4 bit end" in step 4, the process of step 21 and step 22 is performed on the spatial code 4 bit of the vector start point.

In the "start point code bit determination" in step 21, it is determined whether or not the start point spatial code bit indicated by the bit counter is 1, and if it is 1, "two straight line intersection calculation / unnecessary vector" is determined in step 22. "Cut" and find the intersection of the linear equation of the vector and the linear equation of the clipping region edge, and change the start point of the vector to that intersection to clip the unnecessary part of the vector.

Steps 20, 21, 22, 23, and 24 are cutting of the vector with respect to the vector start point, but in the same way, in steps 25, 26, 27, 28, and 29, the vector is cut with respect to the vector end point, and step 30 is performed. The vector which is only in the clipping area with no unnecessary part is output to the output device by "Vector drawing".

For example, if the total number of scans is 1000 and there are an average of 10 run length vectors in 1 scan, and 1/4 of the total run length vectors exist in the clipping area, the following calculation is performed in the entire drawing. It becomes the amount.

In each step, for example, in programming using the FORTRAN language, the amount that can be programmed is about two lines, but only “correction constant calculation” in step 7 requires about 100 lines in FORTRAN. Step 7
Since it is executed only once, it is an amount that can be ignored from the viewpoint of the total calculation amount.

[Problems to be solved by the invention]

Since the conventional clipping method is performed as follows, the coordinate value X (or Y) of the run length vector data before performing the graphic conversion operation does not adopt the property of being constant in the same scan, Since the run-length vector after the graphic conversion calculation is clipped, there is a problem that the determination / calculation process accompanying the clipping becomes complicated and a long calculation time is required.

The present invention has been made to solve the above-mentioned problems, and it is necessary that the coordinate value (X axis or Y axis) of the run length vector data before the graphic conversion operation is constant within the same scan. It is an object of the present invention to provide a clipping method designed to improve the efficiency of calculation by utilizing the clipping process.

[Means for solving problems]

An image clipping method according to the present invention obtains a correction constant used in a conversion calculation expression for correcting image distortion, and calculates where the clipping rectangular area after the conversion calculation by the conversion calculation expression is located before the conversion calculation. The clipping constant used in the inverse transformation calculation formula is obtained, and the Y value of the image for the clipping rectangular area is calculated based on the coordinate value of the X axis.
Calculate the upper or lower limit in the axial direction and perform clipping processing,
The correction constant is applied to execute the conversion arithmetic expression to correct the distortion of the image subjected to the clipping arithmetic processing.

[Action]

The image clipping method according to the present invention uses the fact that the run-length vector data has a constant coordinate value in the same scan when the graphic conversion operation is performed on the run-length vector data to perform clipping. By calculating for each scan and applying it to the run-length vector data in the scan, the processing time is shortened and high-speed graphic clipping processing is realized.

〔Example〕

FIGS. 1- (1) and (2) are flow charts showing an embodiment of the present invention, and the same functions as those in FIGS. 9- (1) and (2) are indicated by the same reference numerals. Fig. 1- (1),
In (2), 31 is a "clipping constant calculation" step, 32 is an "x direction classification" step, 33 is an "out of range" determination step, 34 is a "y direction upper limit calculation" step, and 35 is a "y direction lower limit calculation". Step, 36 is a “start point y ≦ upper limit” determination step, 37 is an “end point y ≧ lower limit” determination step, 38 is a “start point y <lower limit” determination step, 39 is a “start point y = lower limit” step, 40 Is the end point y
> Upper limit ”determination step, and 41 is an“ end point y = upper limit ”step.

First, the outline of the operation of the present invention will be described. (1)
The expression is a conversion expression from (a) to (b) in FIG. 2, but the conversion expression (3) from (b) to (a) is obtained by solving the expression (4).

Next, as shown in FIG. 2, the clipping rectangular area “vertices (x ′ _C1 , y ′ _C1 ), (x ′ _C2 ,
y ′ _C2 ), (x ′ _C3 , y ′ _C3 ), (x ′ _C4 , y ′ _C4 ) ”
Where is located before the conversion operation of equation (1) "vertices (x
_C1 , y _C1 ), (x _C2 , y _C2 ), (x _C3 , y _C3 ),
(X _C4 , y _C4 ) ”is calculated using the equation (3).

Then, the vertices (x
_C1 , y _C1 ) and the vertex (x _C2 , y _C2 ), the vertex (x
_C2 , y _C2 ) and the vertex (x _C3 , y _C3 ), the vertex (x
_C3 , y _C3 ) and the vertex (x _C4 , y _C4 ), the vertex (x
Equation 4 of the straight line connecting _C4 , y _C4 ) and the vertex (x _C1 , y _C1 ).
Ask for a book.

Hereinafter, description will be made based on the example of FIG.

The scan row of the run-length vector before the conversion operation of Expression (1), that is, the x coordinate is less than the x coordinate of the vertex (x _C4 , y _C4 ), or exceeds the x coordinate of the vertex (x _C2 , y _C2 ). If so, the vector is completely outside the clipping region and does not need to be drawn.

The x-coordinate of the run-length vector before conversion in equation (1) is greater than or equal to the x-coordinate of the vertex (x _C4 , y _C4 ), and the vertex (x
_C1 , y _C1 ) is less than the x coordinate, the vertex (x _C3 ,
The straight line connecting y _C3 ) and the vertex (x _C4 , y _C4 ) is the upper limit,
Since the straight line connecting the vertex (x _C4 , y _C4 ) and the vertex (x _C1 , y _C1 ) is the lower limit, a vector outside this range is cut and output to the output device.

Similarly, if the x-coordinate of the run-length vector before conversion in equation (1) is greater than or equal to the x-coordinate of the vertex (x _C1 , y _C1 ) and less than or equal to the x-coordinate of the vertex (x _C3 , y _C3 ). Is the vertex (x
_The straight line connecting _C3 , y _C3 ) and the vertex (x _C4 , y _C4 ) is the upper limit, and the straight line connecting the vertex (x _C1 , y _C1 ) and the vertex (x _C2 , y _C2 ) is the lower limit.

Further, x of the run length vector before the conversion calculation of the equation (1)
If the coordinate exceeds the x coordinate of the vertex (x _C3 , y _C3 ) and is less than or equal to the x coordinate of the vertex (x _C2 , y _C2 ), then
The straight line connecting the vertex (x _C2 , y _C2 ) and the vertex (x _C3 , y _C3 ) is the upper limit, and the vertex (x _C1 , y _C1 ) and the vertex (x _C2 , y _C2 )
The straight line connecting is the lower limit.

The upper and lower limits of the run length vector are checked and unnecessary portions of the vector are cut out as follows.

As shown in FIG. 3, when 42, 43, 44, 45, and 46 are run length vectors in the target scan, 47 is the upper limit, and 48 is the lower limit, first, the y coordinate of the start point of the run length vector is Y that is less than or equal to the upper limit and is the end point
Vectors whose coordinates are greater than or equal to the lower limit, that is, FIG.
Only 44 and 45 are output targets.

Then, if the y coordinate of the starting point is less than or equal to the lower limit for this output target vector, the portion below the lower limit is cut off, and if the y coordinate of the end point of the vector is above the upper limit, the portion above the upper limit is cut out. That is, unnecessary portions of the vectors of FIGS. 43 and 45 are cut off.

Next, the operation will be described in detail based on the flowchart of FIG. First, in the step 7 "correction constant calculation" (1)
The parameters a, b, c, d, e, f, g, and h of the formula are calculated, and in step 31, “In clipping constant calculation (3)
The parameters of the formula a ', b', c ', d', e ', f',
g ', h', and the equations of the straight lines on the four sides of the rectangular area before the calculation of the expression (1) corresponding to the clipping rectangular area after the calculation of the expression (1) are obtained, and the "scan line counter initial setting" in step 8 The initial setting of the target scan line counter is performed in step 9, and if there is no target scan line in the determination of "scan line end" in step 9, the operation is terminated, and the target scan line is determined. If it exists, the process proceeds to step 32.

Then, in the "x direction classification" of step 32, the target scan line is less than the x coordinate of the vertex (x _C4 , y _C4 ) which does not need to be drawn at all, or the x coordinate of the vertex (x _C2 , y _C2 ) is set. or beyond are "ones, or vertex (x _C4, y _C4) or is less than the x-coordinate of the vertex (x _C1, y _C1) in the x-coordinate or more, more x-coordinate of the vertex (x _C1, y _C1) And the vertex (x _C3 ,
x Do is the coordinates following y _C3), to classify or less than the x coordinate of (vertices not exceed the x-coordinate of _{x C3, y C3) (x} C2, y C2).

After step 32, if the target scan line is classified as a line that does not need to be drawn in the “out of range” determination in step 33, the process proceeds to step 12. If it is any other classification, the process proceeds to step 12. Move to 34. Step 1
In the "scan row count-up" of 2, the scan row count is incremented by 1 and the process proceeds to step 9.

In the “y-direction upper limit calculation” of step 34, step 32
The upper limit in the y-direction is obtained based on the classification of No. and the calculation constant in step 31, and the y-direction is similarly obtained in the “y-direction lower limit calculation” in step 35, and in the determination of “in-scan run length end” in step 10. If there is no run length data for which the clipping calculation and the conversion calculation have not been executed in the scan line of interest, the process moves to “scan line count up” in step 12 described above, and if there is, the step is executed. Move to 36.

If the start point y coordinate of the run length vector is less than or equal to the upper limit in the determination of “start point y ≦ upper limit” in step 36, step 3
If it exceeds the upper limit, the process proceeds to step 10. If the y coordinate of the end point of the run length vector is equal to or larger than the lower limit in the determination of "end point y ≧ lower limit" in step 37, the process proceeds to step 38, and if it is less than the lower limit, the process proceeds to step 10.

If the y-coordinate of the start point of the run-length vector is less than the lower limit in the determination of "start point y <lower limit" in step 38, the vector is unnecessary with the y-coordinate of the start point as the lower limit value in "start point y = lower limit" in step 39. Step 40 after cutting off parts
If the y-coordinate of the start point of the run-length vector is not less than the lower limit, the process immediately proceeds to step 40.

Similarly, in step 40 "end point y> upper limit", if the y coordinate of the end point of the run-length vector exceeds the upper limit value, unnecessary portions of the vector are cut out in step 41 "end point y = upper limit".

Then, in "calculation of formula (1)" in step 11, the calculation of formula (1) is performed for the coordinates of the start point and the end point of the vector of the unnecessary portion, and the output device is calculated in "vector drawing" in step 30. Output to.

That is, in step 31, the clipping constant is calculated, in step 8, the scan line is initialized, and in step 9, it is determined whether the scan line is finished. If NO, steps 12, 32, 3
3, 34, 35 are calculated (however, step 3
4 and 35 are executed according to the determination result of step 33), and the step 10, 36, 37, 38, 39, 40, 41, 11 is executed for the run length vector in the scan row in which the run length vector may exist in the clipping area. (However, steps 38, 39, 40, 41, 11
Is only performed on run-length vectors that lie in the clipping region).

For example, the total number of scans is 1000, the average number of run length vectors is 10 in the same scan, and half the scan lines and 1/4 of the total run length vector are in the clipping region. In that case, the calculation amount is approximately as follows in the entire drawing.

Note that each step is a quantity that can be programmed in about two lines in programming using the FORTRAN language, for example. However, steps 7 and 31 require about 100 lines in FORTRAN but are executed only once, so they can be ignored in terms of the total processing amount.

In the above-described embodiment, as shown in FIG. 2, the vertices of the clipping region before the calculation of the expression (1) are the vertexes (x _C4 , y _C4 ), the vertices (x _C1 , y _C1 ), the vertices ( x _C3 , y
_C3 ) and the vertices (x _C2 , y _C2 ) are arranged in this order. Generally, the vertices of the clipping region before the calculation of equation (1) are sorted in ascending order of the x coordinate value, and the vertices (x _C1 , y _C1 ) are obtained. Vertex (x
_C2 , y _C2 ), vertex (x _C2 , y _C2 ) and vertex (x _C3 ,
y _C3 ), vertex (x _C3 , y _C3 ) and vertex (x _C4 , y _C4 ), vertex (x _C4 , y _C4 ) and vertex (x _C1 , y _C1 ) are connected to each other Find the upper and lower limits for.

The graphic conversion operation of the equation (1) may be the high speed operation method shown in Japanese Patent Application No. 60-7213.

Although a part of the rectangular area of the input image after the conversion calculation of the expression (1) is clipped in the above embodiment, the rectangular area may be any rectangular shape. Further, although the example of drawing only the vector inside the clipping area is described, conversely, drawing only the vector outside the clipping area can be similarly realized.

〔The invention's effect〕

As described above, according to the present invention, after the input figure set in a curved manner is scanned at a constant interval to obtain run length data, the correction constant used in the conversion calculation formula for correcting the image distortion is obtained, and , After the clipping process is performed based on the coordinate value that is constant in the same scan, the run length vector subjected to the clipping process is subjected to the distortion correction using the correction constant, so that the processing time is improved by the efficiency of the calculation. There is an effect that it is shortened and high-speed graphic clipping processing can be realized.

[Brief description of drawings]

1- (1) and (2) are flow charts of a clipping method showing an embodiment of the present invention, FIG. 2 is an explanatory view of a clipping area before and after performing a graphic conversion operation, and FIG. FIG. 4 is a general explanatory diagram of a run length vector, FIG. 5 is an explanatory diagram of the entire image area before and after performing a graphic conversion operation, FIG. 6 is a general explanatory diagram of clipping, and FIG. FIG. 7 is an explanatory diagram of a space code in the conventional clipping method, FIG. 8 is an explanatory diagram of clipping of one vector in the conventional clipping method, and FIGS. 9- (1) and (2) are flow charts of the conventional clipping method. FIG. 10 is an image processing system diagram. 11 is a set of operations, (A) is an image input / output device, (B) is an image memory device, and (D) is an image processing device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A graphic is scanned by an image scanner at regular intervals, run length data of the graphic obtained by the scanning is taken into an image memory device, and a conversion arithmetic expression is executed by an image processing device to execute the arithmetic operation In the image clipping method of clipping a part of the rectangular area of the result and outputting it to the output device, a step of obtaining a correction constant used in a conversion arithmetic expression for correcting the distortion of the image, and a step of performing a conversion arithmetic operation after the conversion arithmetic expression A step of obtaining a clipping constant used in an inverse transformation calculation formula for calculating where the clipping rectangular area is located before the transformation operation, and a step of obtaining the clipping rectangular area of the image for the clipping rectangular area based on a coordinate value that is constant in the same scan. Calculate the upper or lower limit in the axial direction orthogonal to the coordinate value and clip The step of graying process, the image clipping method characterized by comprising a step of correcting the distortion of the by applying the correction constant execute the transformation computation equation the clipping processing images.