Convert Lengths Pixel-Wise to Physical¶
Function¶
This Step is used to calculate the actual length of a specified line segment in 2D images. A calibration board is needed when using this Step, and it should be placed in the plane where the line segment to be measured is located.
Sample Scenario¶
This Step is applicable to scenarios where 2D images are used for measuring dimensions of objects with relatively planar surfaces.
Input and Output¶
Parameter Descriptions¶
Parameter |
Description |
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Conversion Method |
Homography |
Calibration Circle Center Distance |
The actual distance between two adjacent circle centers on the the calibration board |
Number of Circle Rows |
The number of rows of circles on the calibration board |
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Number of Circle Columns |
The number of columns of circles on the calibration board |
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Scale |
Scale |
The conversion ratio of pixel distance to actual distance |
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Usage Example¶
Since a line segment to be measured should be input, this Step usually follows Steps with a LineSegmentList output port, such as Measure Distances Segments to Segments, Measure Distances Points to Circles, and Measure Distances Circles to Segments.
Parameter Tuning¶
Conversion Method
Default setting: Scale
Options: Scale, Homography
Description:
Homography: The actual length of the line segment will be calculated by mapping the image plane to the actual plane.
Scale: The actual length of the line segment is equal to the product of the length in pixels multiplied by the scale.
Scale
When the Conversion Method is set to Scale, the input data, parameter, and output result are as shown in the figure below.
- Scale
- Default setting: 1Description: The conversion ratio of pixel distance to actual distance. The specific euqation is: Actual Length of the Line Segment = The Length of the Line Segment in Pixels × Scale.
Homography
When the Conversion Method is set to Homography, the input data, parameter, and output result are as shown in the figure below.
- Calibration Circle Center Distance
- Default setting: 1Description: The actual distance between two circle centers on the the calibration board. Please set the value according to actual situation.
Hint
The distances between centers of adjacent circles in a row or in a column on the calibration board should be the same.
- Number of Circle Rows
- Default setting: 7Description: The number of rows of circles on the calibration board. Please set the value according to actual situation.
- Number of Circle Columns
- Default setting: 7Description: The number of columns of circles on the calibration board. Please set the value according to actual situation.