JP6940261B2 - Image analysis processing device, image analysis processing method, and program - Google Patents

Description

The present invention relates to an image analysis processing apparatus, an image analysis processing method, and a program for processing information obtained by aerial laser measurement.

Conventionally, as a topographic map image generated based on a point cloud data of a terrain obtained by aerial laser measurement, a step color map (Color Map), a shade map (Shaded Map), and the like are widely known. In recent years, there is a technology such as ALB (Airborne LiDAR Bathymetry) that can measure underwater topography such as riverbeds.

By separating the original topographic data into concave parts, convex parts, and flat parts, giving cold colors to the concave parts, and giving warm colors to the convex parts, the topographical part is intended to be clearly illustrated. A drawing device is disclosed in Patent Document 1.

Japanese Unexamined Patent Publication No. 2006-072857

However, in the above-mentioned conventional topographic map creating device, since the height is shown as it is by changing the color, it may be difficult to read the state of the unevenness depending on the order of the unevenness.

The present invention has been made in view of the above circumstances, and provides an image analysis processing apparatus, an image analysis processing method, and a program capable of obtaining an image in which the state of unevenness is emphasized according to the order of unevenness. It is one of the purposes.

The present invention, which solves the problems of the above-mentioned conventional example, is an image analysis processing apparatus, which is a means for receiving point group data of terrain obtained by aerial laser measurement, and a gradient representing a terrain gradient based on the point group data. A gradient image generating means for generating an image, an enhanced image generating means for emphasizing an altitude value obtained based on the point group data and generating an enhanced image representing the enhanced elevation value, and the gradient image. It is intended to include a compositing means for transparently synthesizing the emphasized image to generate a composite image and an output means for outputting the generated composite image.

According to the present invention, it is possible to obtain an image in which the state of unevenness is emphasized according to the order of unevenness.

It is a block diagram which shows the example of the image analysis processing apparatus which concerns on embodiment of this invention. It is a functional block diagram which shows the example of the image analysis processing apparatus which concerns on embodiment of this invention. It is a flowchart which shows the operation example of the image analysis processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the example of the gradient image generated by the image analysis processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the example of the emphasized image generated by the image analysis processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the example of the composite image generated by the image analysis processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows another example of the composite image generated by the image analysis processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows another example of the composite image generated by the image analysis processing apparatus which concerns on embodiment of this invention.

Embodiments of the present invention will be described with reference to the drawings. As illustrated in FIG. 1, the image analysis processing device 1 according to the embodiment of the present invention includes a control unit 11, a storage unit 12, an operation unit 13, and a display unit 14.

The control unit 11 is a program control device such as a CPU, and operates according to a program stored in the storage unit 12. In the present embodiment, the control unit 11 generates a gradient image representing the terrain gradient based on the point cloud data, and emphasizes the altitude value obtained based on the point cloud data, and the enhanced elevation is processed. Generate a highlighted image that represents the value. Then, the control unit 11 transparently synthesizes the gradient image and the emphasized image, generates a composite image, and outputs the composite image. The detailed operation of the control unit 11 will be described later. The storage unit 12 is a disk device, a memory device, or the like, and holds a program executed by the control unit 11. The storage unit 12 also operates as a work memory of the control unit 11.

The operation unit 13 is a mouse, a keyboard, or the like, accepts a user's operation, and outputs information representing the content of the operation to the control unit 11. The display unit 14 is a display or the like, and displays and outputs an image according to an instruction input from the control unit 11.

The data input to the image analysis processing device 1 of the present embodiment includes the point cloud data of the terrain obtained by the aerial laser measurement. Here, as a method of aerial laser measurement, ALB (Airborne Laser Bathymetry) may be used in water areas such as rivers. Further, in the present embodiment, the point cloud data is obtained by aerial laser measurement, but in a water area such as a river, data equivalent to the point cloud data may be obtained by echo sounding or the like.

Here, the operation of the control unit 11 will be described. In the present embodiment, the control unit 11 executes the program stored in the storage unit 12, and as functionally illustrated in FIG. 2, the point cloud data receiving unit 21, the gradient image generation unit 22, and the gradient image generation unit 22 are used. It includes a emphasized image generation unit 23, an emphasized image output unit 24, a compositing processing unit 25, and an output unit 26.

The point cloud data receiving unit 21 receives the input of the point cloud data of the terrain obtained by the aerial laser measurement, and the grid points Pij (xi, yj) (i = 1, 2, ... , J = 1, 2, ...) Is generated, and is output to the gradient image generation unit 22 and the emphasized image generation unit 23. At this time, the point cloud data receiving unit 21 may perform so-called filtering processing on the input point cloud data, and then generate elevation value information for each grid point based on the data after the filtering processing. .. When this filtering process is performed, for example, point cloud data of the ground surface and buildings is obtained, and the altitude value information reflects these.

The gradient image generation unit 22 generates a grayscale gradient image in which the brightness is changed according to the magnitude of the gradient of the terrain based on the input altitude value information. The gradient image generation unit 22 may appropriately set the saturation and hue of the grayscale gradient image to obtain, for example, a gradient image in which the brightness changes with the hue of blue.

The enhanced image generation unit 23 executes an elevation value enhancement process obtained based on the point cloud data input from the point cloud data receiving unit 21. Specifically, this enhancement process is a process that can enhance the altitude value obtained from the point cloud data according to the order (wavelength) of the unevenness of the altitude value, that is, a process that can adjust the wavelength scale. All you need is. Specifically, such emphasis processing includes conversion processing such as localized Fourier transform processing and wavelet transform processing. The operation of the emphasized image generation unit 23 will be described in detail later.

The enhanced image output unit 24 outputs the enhanced image generated by the enhanced image generation unit 23 to the compositing processing unit 25. When there is only one emphasized image generated by the emphasized image generation unit 23, the emphasized image output unit 24 may output the emphasized image as it is to the compositing processing unit 25. Further, when the emphasized image generation unit 23 outputs a plurality of emphasized image candidates, the emphasized image output unit 24 selects one of them according to a predetermined condition, and selects the selected emphasized image candidate. It is output to the compositing processing unit 25 as an emphasized image.

Here, the selection condition may be, for example, a condition specified by the user, or a condition for selection based on the content of each emphasized image candidate.

The compositing processing unit 25 semi-transparently synthesizes (transparently synthesizes) the gradient image generated by the gradient image generation unit 22 and the emphasized image output by the emphasized image output unit 24. Here, the semi-transparent composition means the position (x) of the image data after composition when the values of the pixels at the positions (x, y) corresponding to each other are P (x, y) and Q (x, y), respectively. , Y), the value V (x, y) of the pixel,
V (x, y) = α · P (x, y) + Q (x, y)
It means to determine. Here, α is a positive value. Further, V, P, and Q are, for example, vector values in the RGB color space, and when this calculation is performed for each corresponding component and the result of the calculation V (x, y) exceeds the maximum value as a pixel value, V The value of (x, y) is set to the maximum value. In another example, the value V (x, y) of the pixel at the position (x, y) of the image data after composition is set.
V (x, y) = α · P (x, y) + (1-α) · Q (x, y)
May be defined as. In this example, the value α is a coefficient of synthesis and is 0 ≦ α ≦ 1.

The output unit 26 displays and outputs the composite image generated by the composite processing unit 25 to the display unit 14. Further, the control unit 11 may perform processing such as enlarging a part of the displayed composite image by an instruction operation input from the operation unit 13.

[Generate emphasized image]
Here, the operation of the emphasized image generation unit 23 will be described. The emphasized image generation unit 23 performs wavelet transform processing on the altitude value obtained based on, for example, point cloud data. Specifically, in an example of the present embodiment, the emphasized image generation unit 23 uses the grid points (xi, yj) (i = 1, 2, ..., j = 1, 2, ... ), The wavelet transform process using the Mexican hat type wavelet transform function is executed for the elevation value information Z (xi, yj).

を演算する。ここで、Ψはウェーブレット変換関数であり、例えばメキシカン・ハット型の関数を用いる場合、

とする。また、ａ，ｂは座標値であり、ｓはスケールである。このうちスケールは、経験的に適宜定める。 That is,

Is calculated. Here, Ψ is a wavelet transform function, for example, when using a Mexican hat type function,

And. Further, a and b are coordinate values, and s is a scale. Of these, the scale is empirically determined as appropriate.

The emphasized image generation unit 23 obtains the wavelet transform result C (s, xi, yj) at the coordinate values (xi, yj) for each grid point (xi, yj) for which the altitude value is calculated by the equation (1), and coordinates. Grayscale image data having different brightness according to the corresponding size of C is generated for each pixel corresponding to the value (xi, yj) and output as a highlighted image.

Further, the emphasized image generation unit 23 sets the scales s to a plurality of predetermined scale candidate values σ1, σ2, ..., And generates a plurality of emphasized image candidates (emphasized image candidates) corresponding to each scale candidate value. And output.

Further, the wavelet transform function used by the emphasized image generation unit 23 is not limited to the Mexican-hat type function exemplified in the above equation (2), and a Haar wavelet function, a Morley wavelet function, a Gauss function, or the like may be used. ..

Further, the enhanced image generation unit 23 may use some functions as candidates, generate enhanced image candidates for each of the candidate functions, and output the generated plurality of enhanced image candidates. In this example as well, the emphasized image generation unit 23 further fluctuates the scale candidate value to generate an emphasized image candidate for each function candidate and each scale candidate value, and outputs the generated plurality of emphasized image candidates. May be.

[motion]
The image analysis processing device 1 of the present embodiment has the above configuration and operates as follows. As illustrated in FIG. 3, the image analysis processing device 1 accepts the input of the point cloud data of the terrain obtained by the aerial laser measurement (S1), and the grid points (xi, yj) predetermined in the range of the measured area. ) (I = 1,2, ..., j = 1,2, ...) (for example, a grid point at 1-meter intervals) is generated (S2).

In the following, as an example, the elevation value information of the riverbed in the river will be described as generating the elevation value information based on the point cloud data of ALB (Airborne Laser Bathymetry), but in this embodiment, not only the river but also the flat ground It can be applied to the altitude value information of various places such as mountainous areas and urban areas.

Based on the generated elevation value information, the image analysis processing device 1 generates a grayscale gradient image in which the brightness is changed according to the magnitude of the gradient of the terrain as illustrated in FIG. 4 (S3). .. For example, when the processing target is a river, the saturation and hue of the gradient image may be set to generate a gradient image in which the brightness changes on a blue scale. Note that FIG. 4 is a diagram expressed in black and white for convenience.

Further, the image analysis processing device 1 executes enhancement processing on the altitude value information. That is, the wavelet transform result C (s, xi, yj) at the coordinate values (xi, yj) for each grid point (xi, yj) from which the elevation value information is calculated is obtained by the equation (1) (S4). For each pixel corresponding to the coordinate values (xi, yj), blue scale image data having different brightness according to the corresponding size of C is generated (S5) to obtain an emphasized image. The emphasized image generated here is as illustrated in FIG.

The image analysis processing device 1 semi-transparently synthesizes the gradient image and the emphasized image with each other (S6). The result of this translucent synthesis is as illustrated in FIG. Compared to the example of the emphasized image alone in FIG. 5, according to the semi-transparent composite image of the gradient image as shown in FIG. 6, the outline is clear in the place where the periodic wavy terrain (so-called riverbed wave) is formed. At the same time, an image that emphasizes the altitude value can be obtained. The image analysis processing device 1 displays and outputs the composite image after the translucent composite (S7). After that, the image analysis processing device 1 may perform processing such as enlarging a part of the displayed composite image by an instruction operation input from the operation unit 13, and the image analysis processing device 1 may perform processing such as enlarging and displaying a part of the displayed composite image. , This composite image may be saved as an image data file and sent out via a network.

[Multiple emphasized image candidates]
When the emphasized image generation unit 23 outputs a plurality of emphasized image candidates, the emphasized image output unit 24, for example, synthesizes each emphasized image candidate and a gradient image to generate a composite image candidate, and each of them generates a composite image candidate. The composite image candidate may be displayed and output on the display unit 14. In this case, the user selects a composite image candidate whose desired shape can be clearly visually recognized, and inputs the result of the selection by operating the operation unit 13. The emphasized image output unit 24 outputs the emphasized image candidate corresponding to the selected composite image candidate as an emphasized image. In this example, the emphasized image is selected on condition that the user has selected it.

In another example, the emphasized image output unit 24 uses the lowest brightness value Lmin and the maximum brightness value Lmax among the pixels included in the emphasized image candidate for each emphasized image candidate, and uses the contrast value Lmax / Lmin. Is calculated, and the emphasized image candidate to be the emphasized image is selected based on the condition that the contrast value is the highest value. You may.

In yet another example, when the emphasized image generation unit 23 outputs the emphasized image candidates generated by the wavelet transform using a plurality of scale candidate values σ1, σ2, ..., The undulation pattern represented by the gradient image. The emphasized image candidate corresponding to the scale candidate value closest to the wavelength of may be selected. The wavelength of the undulation pattern can be obtained by Fourier transform or the like.

[Example using the difference from the moving average]
Further, in the description so far, the emphasized image generation unit 23 uses the elevation value information Z (xi, yj) for each grid point (xi, yj) (i = 1, 2, ..., J = 1, 2, ...). On the other hand, the wavelet transform processing is to be executed, but the present embodiment is not limited to this. As another example, the emphasized image generation unit 23 uses a moving average (xi, yj) of altitude value information Z (xi, yj) for each grid point (xi, yj) (i = 1, 2, ..., J = 1, 2, ...). Each grid point is selected as a grid point of interest, and the average of the elevation value information of the grid points at a predetermined distance from the grid point of interest is taken as the moving average value of the elevation value at the grid point of interest), and the grid point is calculated. Wavelet transformation may be performed on the difference Z'(xi, yj) between the moving average value for each and the elevation value of the corresponding grid point. In this example, Z in the above equation (1) is replaced with Z'.

By wavelet transforming the difference from the moving average in this way, it is possible to emphasize the unevenness of the terrain where the average altitude is continuously changing, such as in mountainous areas.

[Contour lines / contour lines]
Further, in the present embodiment, the image analysis processing device 1 may further synthesize the contour lines of the gradient image with respect to the composite image (FIG. 7). In another example, the image analysis processing device 1 may synthesize a contour line (a line segment formed by connecting pixels having the same wavelet transform result value) in the emphasized image with the composite image (FIG. 8). In addition, the image analysis processing device 1 outputs a composite image by selecting either a contour line or a contour line for the composite image by the operation of the user, or does not synthesize the contour line or the contour line. You may choose whether to output the composite image as it is.

When the contour lines are combined, the height of the terrain is clarified, and when the contour lines are combined, the uneven state of the terrain can be clearly seen.

[Another example of unevenness information]
Further, in the description so far, the image analysis processing device 1 targets the unevenness (elevation value) based on the measurement result of the ground surface, and has a gradient image in which the gradient is represented by shading, and the wavelet transform or the like. However, the processing target in the present embodiment is not limited to this.

For example, the operation of the image analysis processing device 1 of the present embodiment can be applied to the unevenness of the surface of the object, such as the unevenness of the surface of the excavated earthenware. Also in this case, the gradient image in which the gradient of the unevenness on the surface of the object is represented by light and shade and the emphasized image in which the unevenness is wavelet-transformed and the converted value is represented by light and shade are semi-transparently combined and output. As a result, the state of unevenness on the surface of the target object can be visually recognized more clearly.

[Effect of Embodiment]
According to the image analysis processing device 1 of the present embodiment, since the enhancement processing is performed according to the scale, it is possible to obtain an image in which the condition of the unevenness is emphasized according to the order of the unevenness.

1 Image analysis processing device, 11 Control unit, 12 Storage unit, 13 Operation unit, 14 Display unit, 21 Point cloud data receiving unit, 22 Gradient image generation unit, 23 Emphasis image generation unit, 24 Emphasis image output unit, 25 Synthesis processing Unit, 26 Output unit.

Claims (4)

A means of accepting topographical point cloud data obtained by aerial laser measurement,
A gradient image generation means for generating a gradient image representing a terrain gradient based on the point cloud data,
An enhanced image generation means that emphasizes the difference between the moving averages of the altitude values obtained based on the point cloud data and generates an emphasized image representing the difference between the highlighted moving averages of the altitude values.
A compositing means for transparently compositing the gradient image and the emphasized image to generate a composite image,
An output means for outputting the generated composite image and
Including
The enhanced image generation means is an image analysis processing device that performs wavelet transform processing on a difference with respect to a moving average of altitude values obtained based on the point cloud data to perform enhancement processing. The image analysis processing apparatus according to claim 1.
The enhanced image generation means obtains a plurality of emphasized image candidates that have been wavelet-transformed using wavelet transform functions of a plurality of scales.
The compositing means is an image analysis processing apparatus that generates the composite image by using the enhanced image selected by selecting one of the enhanced image candidates from the plurality of enhanced image candidates based on predetermined conditions. The process of generating a gradient image representing the terrain gradient based on the point cloud data of the terrain obtained by aerial laser measurement, and
A step of emphasizing the difference of the elevation value obtained based on the point cloud data with respect to the moving average, and generating an emphasized image showing the difference of the emphasized elevation value with respect to the moving average.
A step of transparently synthesizing the gradient image and the emphasized image to generate a composite image, and
The process of outputting the generated composite image and
Including
In the step of generating the emphasized image, an image analysis processing method in which the wavelet transform processing is performed on the difference with respect to the moving average of the altitude value obtained based on the point cloud data to perform the enhancement processing. Computer,
A means of accepting topographical point cloud data obtained by aerial laser measurement,
A gradient image generation means for generating a gradient image representing a terrain gradient based on the point cloud data,
An enhanced image generation means that emphasizes the difference between the moving averages of the altitude values obtained based on the point cloud data and generates an emphasized image representing the difference between the highlighted moving averages of the altitude values.
A compositing means for transparently compositing the gradient image and the emphasized image to generate a composite image,
An output means for outputting the generated composite image and
To function as
An image analysis processing program that causes a computer to perform wavelet transform processing on a difference with respect to a moving average of altitude values obtained based on the point cloud data when functioning as the enhanced image generation means.

Images