CN111915700A - River gradual change graph generation method and device - Google Patents
River gradual change graph generation method and device Download PDFInfo
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- CN111915700A CN111915700A CN202010753707.5A CN202010753707A CN111915700A CN 111915700 A CN111915700 A CN 111915700A CN 202010753707 A CN202010753707 A CN 202010753707A CN 111915700 A CN111915700 A CN 111915700A
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Abstract
The invention provides a river gradual change graph generation method and device, and belongs to the field of river gradual change graph drawing. The method comprises the following steps: projecting the position coordinate array of the river to a screen coordinate system, wherein every two adjacent points in the projected position coordinate array form a line segment, and further all line segments corresponding to the river are obtained; obtaining a river gradual change graph after drawing all line segments corresponding to the river; wherein, the drawing process of a certain line segment is as follows: calculating the coordinates of all pixel points through which the line segment passes; determining the line drawing width corresponding to each pixel point according to the initial width of the river, the final width of the river, the total length of the river and the length from the initial point of the river to the corresponding pixel point; and drawing each pixel point according to the slope of the line segment, the coordinates of the corresponding pixel point and the line drawing width until all pixel points passing through the line segment are drawn. The method can realize the drawing of river gradual change graphs at the pixel level, and has good gradual change effect.
Description
Technical Field
The invention relates to a river gradual change graph generation method and device, and belongs to the technical field of river gradual change graph drawing.
Background
Rivers are one of the common basic geographic elements and are also important contents for the representation of the terrain, and reflect the basic skeleton of the terrain. On the map, in order to visually represent the flow direction and the convergence relationship of the river, the river is generally drawn in a graphically gradual manner. During the manual drawing period, a single line river is generally divided into a plurality of small sections, and then line segments with different widths are drawn for different sections according to the sequence; in the computer aided drawing period, the river is drawn by simulating the manual gradual river flow drawing method, namely the river is divided into a plurality of sections, and the river is drawn by adopting a step method of thickening section by section. Compared with the manual method for drawing the gradually-changed river, the computer-aided drawing method can greatly improve the drawing efficiency and can show the river form to a greater extent, but has the following problems: when the river graph is drawn, the river sections are drawn in a segmented mode firstly, and then the river sections are connected to obtain the whole river graph, so that the drawn rivers are equal in width in the same section, nodes are formed in the change among the sections, the nodes are easy to generate a step effect, the problem that the whole graph is in a step shape is caused, and the river gradual change effect is not ideal.
There are also some methods to solve the above problems, such as: li, wang chen et al published in 2008 mapping and reporting phase 11 of a document named "a single-line river gradual change symbol drawing method", proposed a river gradual change method based on segmented buffer zone technology, which first of all avoids the step-like sudden change by dividing the river into a plurality of differential small segments with a very small distance, and then establishes a buffer zone for each small segment to avoid the disadvantages of too straight line marking, obvious turning and the like; in a document entitled 'implementation of river gradual change effect based on CorelDraw secondary development' disclosed by Yanli in the modern surveying and mapping 2 nd 2019, a river gradual change effect implementation method is provided, width changes of different river sections are determined according to a normal distribution function, and the river gradual change effect is implemented based on CorelDraw secondary development; in a document named as design and development of a gradual river drawing symbol, which is disclosed in 2011 national geometric design and computational academic conference of Chenyongkang, Chengyokang, a gradual river drawing symbol drawing method is provided.
The method improves the stair-stepping problem of river graph drawing by reducing the space of river segmentation, or improves the stair-stepping problem by finely determining the widths of different river segments, or improves the stair-stepping problem by realizing natural transition at nodes, although a certain effect can be achieved, the river graph is drawn in segments fundamentally, the problem that the river is equal in width in the same segment still exists, but the river width is gradually narrowed or widened along with the trend of the river actually, namely, the river width is gradually changed instead of being equal in width, so the method does not realize the river graph size gradual change in the true sense, the drawn river graph is not consistent with the actual situation, and the river gradual change effect is poor.
Disclosure of Invention
The invention aims to provide a river gradual-change graph generation method and a river gradual-change graph generation device, which are used for solving the problem that the gradual-change effect of a river gradual-change graph generated by the conventional method is poor.
In order to achieve the above object, the present invention provides a river gradual change graph generation method, which comprises the following steps:
acquiring a position coordinate array of a river;
projecting the position coordinate array of the river to a screen coordinate system, wherein every two adjacent points in the projected position coordinate array form a line segment, and further all line segments corresponding to the river are obtained;
drawing each line segment of the river to obtain a river gradual change graph after all line segments corresponding to the river are drawn;
wherein, the drawing process of a certain line segment is as follows:
calculating the coordinates of all pixel points through which the line segment passes;
determining the line drawing width corresponding to each pixel point according to the initial width of the river, the final width of the river, the total length of the river and the length from the initial point of the river to the corresponding pixel point;
and drawing each pixel point according to the slope of the line segment, the coordinates of the corresponding pixel point and the line drawing width until all pixel points passing through the line segment are drawn.
The invention also provides a river gradual change pattern generation device which comprises a processor and a memory, wherein the processor executes a computer program stored by the memory to realize the river gradual change pattern generation method.
The invention has the beneficial effects that: the method comprises the steps of firstly determining all line segments of the river, then calculating all pixel points through which each line segment of the river passes, and then completing line segment drawing by drawing each pixel point through which the line segment passes, thereby completing river graph drawing. Factors such as the slope of a line segment where the pixel point is located, the coordinates of the pixel point, the initial width of a river, the termination width of the river, the total length of the river, the length from the initial point of the river to the pixel point and the like are comprehensively considered when the pixel point is drawn, and the precision of the pixel point drawing is ensured; the method can realize the drawing of the river gradual change graph at the pixel level, solves the problem that the traditional segmentation method is easy to generate the step effect when drawing the river gradual change graph, and has better gradual change effect.
Further, in order to realize the calculation of the line width corresponding to the pixel point, in the method and the apparatus, the line width corresponding to each pixel point is calculated by using a line width calculation formula, where the line width calculation formula is: w ═ ws+(we-ws)·LkL, where w is the line width corresponding to the pixel, ws、weRespectively the initial width and the final width of the river, L is the total length of the river, LkThe length of the river from the initial point of the river to the corresponding pixel point along the line.
Further, in order to realize the drawing of the pixel points, in the above method and apparatus, the pixel point (x) on a certain line segmentk，yk) The drawing process comprises the following steps: at a pixel point (x)k，yk) Making a perpendicular to the line segment, and selecting a pixel point (x) on the perpendiculark，yk) The two equidistant side points of (a) are the points (x) on the vertical line and the pixel points (x)k，yk) The distance of (d) is equal to w/2, w is a pixel point (x)k，yk) A corresponding line width; forming a new line segment by the two equidistant side points, and drawing all pixel points which the new line segment passes through to complete pixel points (x)k，yk) Drawing (2).
Further, in the above method and apparatus, a pixel point (x) on a certain line segmentk，yk) The coordinates of the two equidistant side points are respectively (x)k′，yk′)、(xk″，ykAnd ″), calculating the coordinates of two equidistant side points in the screen coordinate system according to the following formulas:
in the formula (I), the compound is shown in the specification,
Δ x is the difference between the abscissa of the two end points of the line segment, and Δ y is the difference between the ordinate of the two end points of the line segment.
Further, in the method and the device, coordinates of all pixel points through which the line segment passes are calculated by adopting a Bresenham algorithm.
Further, in order to make the river drawing effect smoother, in the method and the device, the method further includes a step of smoothing the position coordinate array of the river, and projecting the smoothed position coordinate array of the river to a screen coordinate system.
Further, in the method and the device, the position coordinate array of the river is smoothed by adopting a linear iteration method.
Drawings
FIG. 1 is a flow chart of a river gradual change graph generation method in an embodiment of the method of the present invention;
FIG. 2 is a schematic drawing diagram of a pixel point according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a river gradient pattern in an embodiment of the method of the present invention;
fig. 4 is a view showing the structure of a river gradation pattern generating apparatus in the embodiment of the apparatus of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.
The method comprises the following steps:
with the ordered position coordinate array of a single river as a processing object, the process of generating the river gradient graph of the river by using the river gradient graph generating method of the embodiment shown in fig. 1 is as follows:
step 1, obtaining an original position coordinate array of the river, and performing smoothing processing (for example, smoothing processing by an interpolation method) on the original position coordinate array of the river by adopting a linear iteration method to generate a new position coordinate array of the river so as to ensure that the river drawing effect is smoother.
and projecting the new position coordinate array of the river to a screen coordinate system, wherein every two adjacent points in the projected position coordinate array form a line segment, and further all line segments corresponding to the river are obtained. For example, two adjacent points S (x) in the projected position coordinate arrays，ys)、E(xe，ye) A line segment SE is formed.
Step 3, drawing each line segment of the river, wherein the drawing process of the line segment SE is as follows:
1) calculating coordinates of all pixel points through which the line segment SE passes;
in this embodiment, a Bresenham algorithm is used to calculate coordinates of all pixel points through which each line segment passes, and the method is the prior art and specifically includes the following steps:
first, the slope m of the line segment SE is calculated:
Δx＝xe-xs，Δy＝ye-ysformula (1)
m ═ Δ y/Δ x formula (2)
Then, a corresponding calculation mode is selected according to the size of the slope m of the line segment SE, and the method is mainly divided into the following two cases:
if m is less than or equal to 1, selecting the x-axis direction as the increasing direction, wherein, if x is less than or equal to 1s≤xeThen, each step is increased by 1; if xs＞xeThen each step is incremented by-1. For example, when 0. ltoreq. m.ltoreq.1 and xs≤xeThe following steps are adopted to calculate the pixel point through which the segment SE to be drawn passes:
firstly, taking an endpoint S of a line segment SE to be drawn as a first pixel point, and calculating a discrimination parameter p of the first pixel point0：
② starting from k being 0, in the lineAbscissa value x of each pixelkThe following tests were performed:
if p iskIf < 0, the coordinate of the next pixel point is (x)k+1，yk) And:
pk+1＝pk+ 2. delta. y formula (4)
If p iskIf the coordinate of the next pixel point is greater than or equal to 0, the coordinate of the next pixel point is (x)k+1，yk+1), and:
pk+1＝pk+ 2. delta. y-2. delta. x formula (5)
And thirdly, repeating the step II for delta x-1 times.
If m > 1, then the y-direction is selected as the increasing direction, where if y is greater than 1s≤yeThen, each step is increased by 1; if ys＞yeThen each step is incremented by-1. For example when m > 1 and ys≤yeThe following steps are adopted to calculate the pixel point through which the segment SE to be drawn passes:
firstly, taking an endpoint S of a line segment SE to be drawn as a first pixel point, and calculating a discrimination parameter p of the first pixel point0：
p02.Δ x- Δ y formula (6)
From k to 0, the ordinate value y of each pixel point along the linekThe following tests were performed:
if p iskIf < 0, the coordinate of the next pixel point is (x)k，yk+1), and:
pk+1＝pk+ 2. delta x formula (7)
If p iskIf the coordinate of the next pixel point is greater than or equal to 0, the coordinate of the next pixel point is (x)k+1，yk+1), and:
pk+1＝pk+ 2. delta. x-2. delta. y formula (8)
And thirdly, repeating the step II for delta y-1 times.
2) Calculating the line drawing width corresponding to each pixel point through which the line segment SE passes;
after the Bresenham algorithm is adopted to calculate the coordinates of all pixel points through which the segment SE passes, the line width corresponding to each pixel point can be determined according to the initial width of the river, the final width of the river, the total length of the river and the length from the initial point of the river to the corresponding pixel point along the line.
In this embodiment, a linear interpolation method is used to calculate the line width of each pixel point through which the line segment SE passes, and w is sets、weThe initial width of the river and the final width of the river respectively, L is the total length of the river, LkAny pixel point (x) from the river starting point to the line segment SE passing throughk，yk) Length along the line, pixel point (x)k，yk) The formula for calculating the scribe width w is:
w＝ws+(we-ws)·Lk/L type (9)
Wherein, ws、weNeeds to be determined according to the actual situation of the river.
3) And drawing each pixel point through which the segment SE passes according to the slope of the segment SE, the coordinates of the corresponding pixel points and the line drawing width until all the pixel points through which the segment SE passes are drawn, and finishing the drawing of the segment SE.
To draw any pixel point (x) through which the line segment SE passesk，yk) For example, the slope of the segment SE is m, and the pixel point (x)k，yk) The line width of (a) is w, as shown in FIG. 2, first calculate the pixel point (x)k，yk) Corresponding two equidistant lateral points (x)k′，yk') and (x)k″，yk") by being at a pixel point (x), in particulark，yk) Perpendicular to the line segment SE, and selecting a pixel point (x) on the perpendiculark，yk) Two pixel points with the distance equal to w/2 are taken as pixel points (x)k，yk) Two equidistant lateral points of (a).
In the screen coordinate system, the positive direction of the y axis is downward, the positive direction of the x axis is rightward, and the equidistant lateral points (x)k′，yk') and (x)k″，yk") coordinate is calculated as follows:
in the formula (I), the compound is shown in the specification,
Δ x is the difference between the abscissa of the two end points of the segment SE, and Δ y is the difference between the ordinate of the two end points of the segment SE; of course, the slope m of the line segment SE may be calculated by using the coordinates of the two end points of the line segment SE, and α ═ tan may be calculated-1m, and further obtaining sin alpha and cos alpha.
Then, the equidistant lateral points (x)k′，yk') and (x)k″，yk") as two end points of the new line segment to form a new line segment, and using Bresenham algorithm to obtain all pixel points passed by the new line segment and draw the pixel points, thereby completing the pixel points (x)k，yk) Drawing (2).
And 4, obtaining a river gradual change graph after drawing all line segments corresponding to the river.
Repeating the step 3 for all the line segments of the river to generate a river gradient graph, and the result is shown in fig. 3. It can be seen that the river gradual change graph drawn by the method is rich in details and good in rendering effect.
The river gradual change graph generation method comprises the step of smoothing an original position coordinate array of a river, and aims to obtain position coordinate data of more rivers by smoothing the original position coordinate array of the river, so that the river drawing effect is ensured to be smoother; as another embodiment, if the acquired raw position coordinate array of the river already contains a sufficient amount of river position coordinate data to obtain an ideal river drawing effect, the step of smoothing may be omitted, and the acquired raw position coordinate array of the river may be directly subjected to subsequent processing to obtain an ideal river gradient pattern.
The embodiment of the device is as follows:
as shown in fig. 4, the river gradual change pattern generation apparatus of the present embodiment includes a processor, a memory, and a computer program that is executable on the processor is stored in the memory, and the processor implements the method in the above method embodiments when executing the computer program.
That is, the method in the above method embodiment is understood as a flow of the river gradation pattern generation method that can be realized by computer program instructions. These computer program instructions may be provided to a processor such that execution of the instructions by the processor results in the implementation of the functions specified in the method flow described above.
The processor referred to in this embodiment refers to a processing device such as a microprocessor MCU or a programmable logic device FPGA.
The memory referred to in this embodiment includes a physical device for storing information, and generally, information is digitized and then stored in a medium using an electric, magnetic, optical, or the like. For example: various memories for storing information by using an electric energy mode, such as RAM, ROM and the like; various memories for storing information by magnetic energy, such as hard disk, floppy disk, magnetic tape, magnetic core memory, bubble memory, and U disk; various types of memory, CD or DVD, that store information optically. Of course, there are other ways of memory, such as quantum memory, graphene memory, and so forth.
The apparatus comprising the memory, the processor and the computer program is realized by the processor executing corresponding program instructions in the computer, and the processor can be loaded with various operating systems, such as windows operating system, linux system, android, iOS system, and the like.
Claims (8)
1. A river gradual change graph generation method is characterized by comprising the following steps:
acquiring a position coordinate array of a river;
projecting the position coordinate array of the river to a screen coordinate system, wherein every two adjacent points in the projected position coordinate array form a line segment, and further all line segments corresponding to the river are obtained;
drawing each line segment of the river to obtain a river gradual change graph after all line segments corresponding to the river are drawn;
wherein, the drawing process of a certain line segment is as follows:
calculating the coordinates of all pixel points through which the line segment passes;
determining the line drawing width corresponding to each pixel point according to the initial width of the river, the final width of the river, the total length of the river and the length from the initial point of the river to the corresponding pixel point;
and drawing each pixel point according to the slope of the line segment, the coordinates of the corresponding pixel point and the line drawing width until all pixel points passing through the line segment are drawn.
2. The river gradual change graph generation method according to claim 1, wherein the line width corresponding to each pixel point is calculated by using a line width calculation formula, wherein the line width calculation formula is as follows: w ═ ws+(we-ws)·LkL, where w is the line width corresponding to the pixel, ws、weRespectively the initial width and the final width of the river, L is the total length of the river, LkThe length of the river from the initial point of the river to the corresponding pixel point along the line.
3. The river gradual change graphic generation method as claimed in claim 1 or 2, wherein a pixel point (x) on a certain line segmentk,yk) The drawing process comprises the following steps: at a pixel point (x)k,yk) Making a perpendicular to the line segment, and selecting a pixel point (x) on the perpendiculark,yk) The two equidistant side points of (a) are the points (x) on the vertical line and the pixel points (x)k,yk) The distance of (d) is equal to w/2, w is a pixel point (x)k,yk) A corresponding line width; forming a new line segment by the two equidistant side points, and drawing all pixel points which the new line segment passes through to complete pixel points (x)k,yk) Drawing (2).
4. The river gradual change pattern generation method as claimed in claim 3, wherein a pixel point (x) on a certain line segmentk,yk) The coordinates of the two equidistant side points are respectively (x)k′,yk′)、(xk″,ykAnd ″), calculating the coordinates of two equidistant side points in the screen coordinate system according to the following formulas:
in the formula (I), the compound is shown in the specification,
Δ x is the difference between the abscissa of the two end points of the line segment, and Δ y is the difference between the ordinate of the two end points of the line segment.
5. The river gradual change graphic generation method according to claim 1, wherein coordinates of all pixel points through which the line segment passes are calculated by using Bresenham's algorithm.
6. The river gradation pattern generation method as claimed in claim 1, further comprising a step of smoothing the position coordinate array of the river, and projecting the smoothed position coordinate array of the river to a screen coordinate system.
7. The river gradation pattern generation method according to claim 6, wherein the position coordinate array of the river is smoothed by a linear iteration method.
8. A river gradation pattern generation apparatus characterized by comprising a processor and a memory, the processor executing a computer program stored by the memory to implement the river gradation pattern generation method according to any one of claims 1 to 7.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113157820A (en) * | 2021-03-31 | 2021-07-23 | 生态环境部卫星环境应用中心 | Buffer zone automatic segmentation and classification method and device suitable for winding river |
| CN113554731A (en) * | 2021-06-25 | 2021-10-26 | 深圳市震有软件科技有限公司 | Visualization method and device for river water quality, storage medium and terminal equipment |
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2020
- 2020-07-30 CN CN202010753707.5A patent/CN111915700A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113157820A (en) * | 2021-03-31 | 2021-07-23 | 生态环境部卫星环境应用中心 | Buffer zone automatic segmentation and classification method and device suitable for winding river |
| CN113157820B (en) * | 2021-03-31 | 2023-07-21 | 生态环境部卫星环境应用中心 | Automatic segmentation and classification method and device for buffer zone suitable for serpentine river |
| CN113554731A (en) * | 2021-06-25 | 2021-10-26 | 深圳市震有软件科技有限公司 | Visualization method and device for river water quality, storage medium and terminal equipment |
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