measure_posT_measure_posMeasurePosMeasurePosmeasure_pos (算子)

名称

measure_posT_measure_posMeasurePosMeasurePosmeasure_pos — 提取垂直于矩形或环形弧的直边。

签名

描述

measure_posmeasure_posMeasurePosMeasurePosMeasurePosmeasure_pos extracts straight edges which lie perpendicular to the major axis of a rectangle or annular arc.

For an explanation of the concept of 1D measuring see the introduction of chapter 一维测量。

The algorithm of measure_posmeasure_posMeasurePosMeasurePosMeasurePosmeasure_pos works by averaging the gray values in “slices” perpendicular to the major axis of the rectangle or annular arc in order to obtain a one-dimensional edge profile. The sampling is done at subpixel positions in the image ImageImageImageImageimageimage at integer row and column distances (in the coordinate frame of the rectangle) from the center of the rectangle. Since this involves some calculations which can be used repeatedly in several measurements, the operator gen_measure_rectangle2gen_measure_rectangle2GenMeasureRectangle2GenMeasureRectangle2GenMeasureRectangle2gen_measure_rectangle2 or gen_measure_arcgen_measure_arcGenMeasureArcGenMeasureArcGenMeasureArcgen_measure_arc is used to perform these calculations only once, thus increasing the speed of measure_posmeasure_posMeasurePosMeasurePosMeasurePosmeasure_pos significantly. Since there is a trade-off between accuracy and speed in the subpixel calculations of the gray values, and thus in the accuracy of the extracted edge positions, different interpolation schemes can be selected in gen_measure_rectangle2gen_measure_rectangle2GenMeasureRectangle2GenMeasureRectangle2GenMeasureRectangle2gen_measure_rectangle2。(The interpolation only influences rectangles not aligned with the image axes.) The measure object generated with gen_measure_rectangle2gen_measure_rectangle2GenMeasureRectangle2GenMeasureRectangle2GenMeasureRectangle2gen_measure_rectangle2 is passed in MeasureHandleMeasureHandleMeasureHandleMeasureHandlemeasureHandlemeasure_handle。

After the one-dimensional edge profile has been calculated, subpixel edge locations are computed by convolving the profile with the derivatives of a Gaussian smoothing kernel of standard deviation SigmaSigmaSigmaSigmasigmasigma. Salient edges can be selected with the parameter ThresholdThresholdThresholdThresholdthresholdthreshold, which constitutes a threshold on the amplitude values (AmplitudeAmplitudeAmplitudeAmplitudeamplitudeamplitude), i.e., the absolute value of the first derivative of the edge. Note that the amplitude values are scaled by the factor . Additionally, it is possible to select only positive edges, i.e., edges which constitute a dark-to-light transition in the direction of the major axis of the rectangle or the arc (TransitionTransitionTransitionTransitiontransitiontransition = 'positive'"positive""positive""positive""positive""positive"), only negative edges, i.e., light-to-dark transitions (TransitionTransitionTransitionTransitiontransitiontransition = 'negative'"negative""negative""negative""negative""negative"), or both types of edges (TransitionTransitionTransitionTransitiontransitiontransition = 'all'"all""all""all""all""all"). Finally, it is possible to select which edge points are returned. If SelectSelectSelectSelectselectselect is set to 'all'"all""all""all""all""all", all edge points are returned. If it is set to 'first'"first""first""first""first""first", only the first of the extracted edge points is returned, while it is set to 'last'"last""last""last""last""last", only the last one is returned.

The extracted edges are returned as single points which lie on the major axis of the rectangle or arc in (RowEdgeRowEdgeRowEdgeRowEdgerowEdgerow_edge, ColumnEdgeColumnEdgeColumnEdgeColumnEdgecolumnEdgecolumn_edge). The corresponding edge amplitudes are returned in AmplitudeAmplitudeAmplitudeAmplitudeamplitudeamplitude. In addition, the distance between consecutive edge points is returned in DistanceDistanceDistanceDistancedistancedistance. Here, Distance[i] corresponds to the distance between Edge[i] and Edge[i+1], i.e., the tuple DistanceDistanceDistanceDistancedistancedistance contains one element less than the tuples RowEdgeRowEdgeRowEdgeRowEdgerowEdgerow_edge and ColumnEdgeColumnEdgeColumnEdgeColumnEdgecolumnEdgecolumn_edge。

注意

measure_posmeasure_posMeasurePosMeasurePosMeasurePosmeasure_pos only returns meaningful results if the assumptions that the edges are straight and perpendicular to the major axis of the rectangle or arc are fulfilled. Thus, it should not be used to extract edges from curved objects, for example. Furthermore, the user should ensure that the rectangle or arc is as close to perpendicular as possible to the edges in the image. Additionally, SigmaSigmaSigmaSigmasigmasigma must not become larger than approx. 0.5 * Length1 (for Length1 see gen_measure_rectangle2gen_measure_rectangle2GenMeasureRectangle2GenMeasureRectangle2GenMeasureRectangle2gen_measure_rectangle2).

It should be kept in mind that measure_posmeasure_posMeasurePosMeasurePosMeasurePosmeasure_pos ignores the domain of ImageImageImageImageimageimage for efficiency reasons. If certain regions in the image should be excluded from the measurement a new measure object with appropriately modified parameters should be generated.

执行信息

• 多线程类型：可重入（与非独占算子并行运行）。
• 多线程作用域：全局（可从任何线程调用）。
• 未采用并行化处理。

参数

结果

如果参数值正确，算子 measure_posmeasure_posMeasurePosMeasurePosMeasurePosmeasure_pos 返回值 2 ( H_MSG_TRUE )。否则将抛出异常。

可能的前趋

gen_measure_rectangle2gen_measure_rectangle2GenMeasureRectangle2GenMeasureRectangle2GenMeasureRectangle2gen_measure_rectangle2

可能的后继

close_measureclose_measureCloseMeasureCloseMeasureCloseMeasureclose_measure

替代

edges_sub_pixedges_sub_pixEdgesSubPixEdgesSubPixEdgesSubPixedges_sub_pix, fuzzy_measure_posfuzzy_measure_posFuzzyMeasurePosFuzzyMeasurePosFuzzyMeasurePosfuzzy_measure_pos

另见

measure_pairsmeasure_pairsMeasurePairsMeasurePairsMeasurePairsmeasure_pairs, fuzzy_measure_pairsfuzzy_measure_pairsFuzzyMeasurePairsFuzzyMeasurePairsFuzzyMeasurePairsfuzzy_measure_pairs, fuzzy_measure_pairingfuzzy_measure_pairingFuzzyMeasurePairingFuzzyMeasurePairingFuzzyMeasurePairingfuzzy_measure_pairing

模块

一维计量

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