align_metrology_model🔗
Short description🔗
align_metrology_model — Alignment of a metrology model.
Signature🔗
align_metrology_model( metrology_model MetrologyHandle, real Row, real Column, angle.rad Angle )
Description🔗
align_metrology_model moves and rotates the whole metrology model
MetrologyHandle
relative to the image coordinate system which has its origin in the
top left corner.
For an explanation of the concept of 2D metrology see the introduction of chapter 2D Metrology.
An alignment ensures, that the position and
orientation of the metrology model is adapted to the
objects to be measured in the current image. The alignment is then
used by apply_metrology_model to perform the measurement.
First the metrology model is rotated by Angle, then
the metrology model is translated by Row and Column.
The values of the alignment are overwritten by the
next call of align_metrology_model.
Computation of the parameters of the alignment🔗
The parameters of the alignment can be determined using diverse methods. Here, three possibilities to determine the parameters are listed:
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Using region analysis: If the metrology model can be extracted using region processing and if the pose of the Region changes only slightly in subsequent images, the parameters of the reference system of the metrology model and of the alignment can be derived using region analysis. In the following picture
thresholdandsmallest_rectangle2were used to obtain these parameter.
The region extracted with
thresholdis shown in red. The rectangle computed withsmallest_rectangle2is shown in green.-
Setting the reference system
In the image in which the metrology model was defined, extract a region containing the metrology objects. The pose of this region with respect to the image coordinate system is determined and set as the reference system of the metrology model using
set_metrology_model_param. This step is only performed once when setting up the metrology model.Example:
threshold(Image, Region, 0, 50)smallest_rectangle2(Region, RowOrig, ColumnOrig, AngleOrig, Length1, Length2)set_metrology_model_param(MetrologyHandle, 'reference_system', [RowOrig, ColumnOrig, AngleOrig]) -
Determining the alignment
In an image where the metrology model occurs in a different Pose, the current pose if the extracted region is determined. This pose is then used to align the metrology model.
Example:
threshold(CurrentImage, Region, 0, 50)smallest_rectangle2(Region, RowAlign, ColumnAlign, AngleAlign, Length1, Length2)align_metrology_model(MetrologyHandle, RowAlign, ColumnAlign, AngleAlign)
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Using a shape model: If a shape model is used to align the metrology model, the reference system with respect to which the metrology objects are given has to be set so that it coincides with the coordinate system used by the shape model. Only then, the results ('row', 'column', 'angle') of
get_generic_shape_model_resultcan be used directly inalign_metrology_modelto align the metrology model in the current image. The individual steps that are needed, are shown below.
(1) (2) (3) (1) The contours of the metrology model (2) The contours of the shape model (3) The contours of the metrology model after setting the correct reference system.
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Setting the reference system
In the image in which the metrology model was defined, the pose of the origin of the shape model is determined and set as the reference system of the metrology model using
set_metrology_model_param. This step is only performed once when setting up the metrology model.Example:
train_generic_shape_model(Image, ModelID)area_center(Image, Area, RowOrig, ColumnOrig)set_metrology_model_param(MetrologyHandle, 'reference_system', [RowOrig, ColumnOrig, 0]) -
Determining the alignment
In an image, in which the object to be measured occurs in a different pose, the current pose of the shape model is determined and set in the metrology model using
align_metrology_model.Example:
find_generic_shape_model(CurrentImage, ModelID, MatchResultID, NumMatchResult)get_generic_shape_model_result(MatchResultID, 'all', 'row', RowAlign)get_generic_shape_model_result(MatchResultID, 'all', 'column', ColumnAlign)get_generic_shape_model_result(MatchResultID, 'all', 'angle', AngleAlign)align_metrology_model(MetrologyHandle, RowAlign, ColumnAlign, AngleAlign)
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Using a rigid 2D transformation: If certain model points (given as [PRowModel], [PColumnModel]) can be clearly identified and if they can still be clearly identified in further images in which the objects to be measured can occur shifted or rotated, a rigid transformation can be calculated between those points. The transformation parameters can then directly be used for aligning the model. In this case, the reference point of the metrology model does not have to be changed.
(1) (2) (1) The contours of the metrology object and the four corresponding points in the image that was used for the creation of the metrology model. (2) The contours of the metrology object and the four corresponding points in a new image.
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Determine the point correspondences
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Estimate the model pose
The following operator sequence calculates the parameters of the model pose (
Row,Column,Angle) from corresponding points in the model image and one other image.Example:
vector_to_rigid(PRowModel, PColumnModel, PRowCurrent, PColumnCurrent, HomMat2D)hom_mat2d_to_affine_par(HomMat2D, Sx, Sy, Angle, Theta, Row, Column)
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Execution information🔗
Execution information
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Multithreading type: reentrant (runs in parallel with non-exclusive operators).
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Multithreading scope: global (may be called from any thread).
-
Processed without parallelization.
This operator modifies the state of the following input parameter:
During execution of this operator, access to the value of this parameter must be synchronized if it is used across multiple threads.
Parameters🔗
MetrologyHandle (input_control, state is modified) metrology_model → (handle)
Handle of the metrology model.
Row (input_control) real → (real / integer)
Row coordinate of the alignment.
Default: 0
Column (input_control) real → (real / integer)
Column coordinate of the alignment.
Default: 0
Angle (input_control) angle.rad → (real / integer)
Rotation angle of the alignment.
Default: 0
Example🔗
(HDevelop)
read_image (Image, 'metal-parts/circle_plate_01')
create_metrology_model (MetrologyHandle)
get_image_size (Image, Width, Height)
set_metrology_model_image_size (MetrologyHandle, Width, Height)
CircleParam := [354,274,53]
CircleParam := [CircleParam,350,519,53]
add_metrology_object_generic (MetrologyHandle, 'circle', CircleParam, 20,\
5, 1, 30, [], [], CircleIndices)
create_generic_shape_model (ModelID)
set_generic_shape_model_param (ModelID, 'metric', 'use_polarity')
set_generic_shape_model_param (ModelID, 'min_contrast', 20)
train_generic_shape_model (Image, ModelID)
* Determine location of shape model origin
area_center (Image, Area, RowOrigin, ColOrigin)
set_metrology_model_param (MetrologyHandle, 'reference_system', \
[RowOrigin,ColOrigin,0])
read_image (CurrentImage, 'metal-parts/circle_plate_02')
find_generic_shape_model (CurrentImage, ModelID, MatchResultID, \
NumMatchResult)
get_generic_shape_model_result (MatchResultID, 'all', 'row', Row)
get_generic_shape_model_result (MatchResultID, 'all', 'column', Col)
get_generic_shape_model_result (MatchResultID, 'all', 'angle', Angle)
align_metrology_model (MetrologyHandle, Row, Col, Angle)
apply_metrology_model (CurrentImage, MetrologyHandle)
get_metrology_object_result (MetrologyHandle, CircleIndices, 'all', \
'result_type', 'all_param', Rectangle)
get_metrology_object_result_contour (Contour, MetrologyHandle, \
CircleIndices, 'all', 1.5)
Result🔗
If the parameters are valid, the operator
align_metrology_model returns the value 2 (H_MSG_TRUE).
If necessary, an exception is raised.
Combinations with other operators🔗
Combinations
Possible predecessors
set_metrology_model_param, add_metrology_object_generic
Possible successors
See also
Module🔗
2D Metrology