Operators

prepare_variation_model (Operator)

Name

prepare_variation_model — Prepare a variation model for comparison with an image.

Signature

prepare_variation_model( : : ModelID, AbsThreshold, VarThreshold : )

Description

prepare_variation_model prepares a variation model for the image comparison with compare_variation_model or compare_ext_variation_model. This is done by converting the ideal image and the variation image that have been trained with train_variation_model into two threshold images and storing them in the variation model. These threshold images are used in compare_variation_model or compare_ext_variation_model to speed up the comparison of the current image to the variation model.

Two thresholds are used to compute the threshold images. The parameter AbsThreshold determines the minimum amount of gray levels by which the image of the current object must differ from the image of the ideal object. The parameter VarThreshold determines a factor relative to the variation image for the minimum difference of the current image and the ideal image. AbsThreshold and VarThreshold each can contain one or two values. If two values are specified, different thresholds can be determined for too bright and too dark pixels. In this mode, the first value refers to too bright pixels, while the second value refers to too dark pixels. If one value is specified, this value refers to both the too bright and too dark pixels. Let i(x,y) be the ideal image, v(x,y) the variation image, a{u}=AbsThreshold, a{l}=AbsThreshold, b{u}=VarThreshold, and b{l}=VarThreshold (or a{u}=AbsThreshold, a{l}=AbsThreshold, b{u}=VarThreshold, and b{l}=VarThreshold, respectively). Then the two threshold images t{u,l} are computed as follows:

t{u}(x,y) = i(x,y) + max{a{u},b{u}*v(x,y)}
t{l}(x,y) = i(x,y) - max{a{l},b{l}*v(x,y)}

If the current image c(x,y) is compared to the variation model using compare_variation_model, the output region contains all points that differ substantially from the model, i.e., that fulfill the following condition:

c(x,y) > t{u}(x,y) or c(x,y) < t{l}(x,y) .

In compare_ext_variation_model, extended comparison modes are available, which return only too bright errors, only too dark errors, or bright and dark errors as separate regions.

After the threshold images have been created they can be read out with get_thresh_images_variation_model. Furthermore, the training data can be deleted with clear_train_data_variation_model to save memory.

Parallelization

• Multithreading type: exclusive (runs in parallel only with independent operators).
• Processed without parallelization.

Parameters

ModelID (input_control)  variation_model (integer)

ID of the variation model.

AbsThreshold (input_control)  number(-array) (real / integer)

Absolute minimum threshold for the differences between the image and the variation model.

Default value: 10

Suggested values: 0, 5, 10, 15, 20, 30, 40, 50

Restriction: AbsThreshold >= 0

VarThreshold (input_control)  number(-array) (real / integer)

Threshold for the differences based on the variation of the variation model.

Default value: 2

Suggested values: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5

Restriction: VarThreshold >= 0

Result

prepare_variation_model returns 2 (H_MSG_TRUE) if all parameters are correct.