depth_from_focusdepth_from_focusDepthFromFocusDepthFromFocus (Operator)


depth_from_focusdepth_from_focusDepthFromFocusDepthFromFocus — Extract depth using multiple focus levels.


depth_from_focus(MultiFocusImage : Depth, Confidence : Filter, Selection : )

Herror depth_from_focus(const Hobject MultiFocusImage, Hobject* Depth, Hobject* Confidence, const char* Filter, const char* Selection)

Herror T_depth_from_focus(const Hobject MultiFocusImage, Hobject* Depth, Hobject* Confidence, const Htuple Filter, const Htuple Selection)

void DepthFromFocus(const HObject& MultiFocusImage, HObject* Depth, HObject* Confidence, const HTuple& Filter, const HTuple& Selection)

HImage HImage::DepthFromFocus(HImage* Confidence, const HTuple& Filter, const HTuple& Selection) const

HImage HImage::DepthFromFocus(HImage* Confidence, const HString& Filter, const HString& Selection) const

HImage HImage::DepthFromFocus(HImage* Confidence, const char* Filter, const char* Selection) const

HImage HImage::DepthFromFocus(HImage* Confidence, const wchar_t* Filter, const wchar_t* Selection) const   (Windows only)

static void HOperatorSet.DepthFromFocus(HObject multiFocusImage, out HObject depth, out HObject confidence, HTuple filter, HTuple selection)

HImage HImage.DepthFromFocus(out HImage confidence, HTuple filter, HTuple selection)

HImage HImage.DepthFromFocus(out HImage confidence, string filter, string selection)


The operator depth_from_focusdepth_from_focusDepthFromFocusDepthFromFocusDepthFromFocus extracts the depth using a focus sequence. The images of the focus sequence have to passed as a multi channel image (MultiFocusImageMultiFocusImageMultiFocusImageMultiFocusImagemultiFocusImage). The depth for each pixel will be returned in DepthDepthDepthDepthdepth as the channel number. The parameter ConfidenceConfidenceConfidenceConfidenceconfidence returns a confidence value for each depth estimation: The larger this value, the higher the confidence of the depth estimation is.

depth_from_focusdepth_from_focusDepthFromFocusDepthFromFocusDepthFromFocus selects the pixels with the best focus of all focus levels. The method used to extract these pixels is specified by the parameters FilterFilterFilterFilterfilter and SelectionSelectionSelectionSelectionselection.

For the parameter FilterFilterFilterFilterfilter, you can choose between the values 'highpass'"highpass""highpass""highpass""highpass" and 'bandpass'"bandpass""bandpass""bandpass""bandpass". To determine the focus within the image a high- or a bandpass filter can be applied. The larger the filter response, the more in focus is the image at this location. Compared to the highpass filter, the bandpass filter suppresses high frequencies. This is useful in particular in images containing strong noise.

Optionally, you can smooth the filtered image using the mean filter by passing two additional integer values for the mask size in the parameter FilterFilterFilterFilterfilter (e.g., ['highpass'"highpass""highpass""highpass""highpass", 7, 7]). This blurs the in-focus region with neighboring pixels and thus allows to bridge small areas with no texture within the image. Note, however, that this smoothing does not suppress noise in the original image, since it is applied only after high- or bandpass filtering.

The parameter SelectionSelectionSelectionSelectionselection determines how the optimum focus level is selected. If you pass the value 'next_maximum'"next_maximum""next_maximum""next_maximum""next_maximum", the closest focus maximum in the neighborhood is used. In contrast, if you pass the value 'local'"local""local""local""local", the focus level is determined based on the focus values of all focus levels of the pixel. With 'next_maximum'"next_maximum""next_maximum""next_maximum""next_maximum", you typically achieve a slightly smoothed and more robust result.

This additional smoothing is useful if no telecentric lenses are used to take the input images. In this case, the position of an object will slightly shift within the sequence. By adding appropriate smoothing, this effect can be partially compensated.


If MultiFocusImageMultiFocusImageMultiFocusImageMultiFocusImagemultiFocusImage contains more than 255 channels (focus levels), DepthDepthDepthDepthdepth is clipped at 255, i.e. depth values higher than 255 are ignored.

If the filter mask for FilterFilterFilterFilterfilter is specified with even values, the routine uses the next larger odd values instead (this way the center of the filter mask is always explicitly determined).

If SelectionSelectionSelectionSelectionselection is set to 'local'"local""local""local""local" and FilterFilterFilterFilterfilter is set to 'highpass'"highpass""highpass""highpass""highpass" or 'bandpass'"bandpass""bandpass""bandpass""bandpass", depth_from_focusdepth_from_focusDepthFromFocusDepthFromFocusDepthFromFocus can be executed on OpenCL devices. If smoothing is enabled, the same restrictions and limitations as for mean_imagemean_imageMeanImageMeanImageMeanImage apply.

Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.

Execution Information


MultiFocusImageMultiFocusImageMultiFocusImageMultiFocusImagemultiFocusImage (input_object)  multichannel-image(-array) objectHImageHImageHobject (byte)

Multichannel gray image consisting of multiple focus levels.

DepthDepthDepthDepthdepth (output_object)  singlechannelimage(-array) objectHImageHImageHobject * (byte)

Depth image.

ConfidenceConfidenceConfidenceConfidenceconfidence (output_object)  singlechannelimage(-array) objectHImageHImageHobject * (byte)

Confidence of depth estimation.

FilterFilterFilterFilterfilter (input_control)  string(-array) HTupleHTupleHtuple (string / integer) (string / int / long) (HString / Hlong) (char* / Hlong)

Filter used to find sharp pixels.

Default value: 'highpass' "highpass" "highpass" "highpass" "highpass"

Suggested values: 'highpass'"highpass""highpass""highpass""highpass", 'bandpass'"bandpass""bandpass""bandpass""bandpass", 3, 5, 7, 9

SelectionSelectionSelectionSelectionselection (input_control)  string(-array) HTupleHTupleHtuple (string) (string) (HString) (char*)

Method used to find sharp pixels.

Default value: 'next_maximum' "next_maximum" "next_maximum" "next_maximum" "next_maximum"

List of values: 'local'"local""local""local""local", 'next_maximum'"next_maximum""next_maximum""next_maximum""next_maximum"

List of values (for compute devices): 'local'"local""local""local""local"

Example (C++ (HALCON 5.0-10.0))


Possible Predecessors

compose2compose2Compose2Compose2Compose2, compose3compose3Compose3Compose3Compose3, compose4compose4Compose4Compose4Compose4, add_channelsadd_channelsAddChannelsAddChannelsAddChannels, read_imageread_imageReadImageReadImageReadImage, read_sequenceread_sequenceReadSequenceReadSequenceReadSequence

Possible Successors

select_grayvalues_from_channelsselect_grayvalues_from_channelsSelectGrayvaluesFromChannelsSelectGrayvaluesFromChannelsSelectGrayvaluesFromChannels, mean_imagemean_imageMeanImageMeanImageMeanImage, binomial_filterbinomial_filterBinomialFilterBinomialFilterBinomialFilter, gauss_filtergauss_filterGaussFilterGaussFilterGaussFilter, thresholdthresholdThresholdThresholdThreshold

See also



3D Metrology