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Description

The blob tools isolate and gather statistics about parts of an image. A blob is a isolated part of an image defined by a given threshold. Blobs can be judged based on area, perimeter, shape, location, color intensity, width, height, etc.

Technically a blob is a point with extra data included that a typical point does not have. Consequently, a set of blobs can be passed to other tools as a set of points, one point for each blob. The point value for a blob can also be weighted using the Blob to Points tool so that larger blobs, for example, contain more points than smaller blob.

Practical uses for blob tools

Using the blob tools

In order to do any type of blob analysis on an image the blobs must first be determined. The Blob tool will accomplish this. The Blob tool sets the blob threshold to determine what is considered a blob and what is not. It also ecords the statistics for each blob that are found and can sort the blobs according to various criteria. Once the blobs are determined it may be necessary to run tests based on a specific set of the blobs that have been determined. The Blob Filter tool will eliminate and maintain blobs based on user defined criteria.

Analysis can also be done on holes in a blob (Blob Children), the results for a given blob can be setup as a set of parameters (Blob Select) and color intensity (Blob Colors) of blobs can be stored in a program for later use.

The blob filter is the most basic blob analysis tool. For any blob analysis to be done this tool must be used first.

Using the Blob Finder

  1. Grab an image so it displays on the viewer.
  2. On the parameters property page set the thresholds (or right click to use the threshold option); on the blob tool either for auto thresholding dor dark blobs or light blobs or do a manual setup.  The thresholds determine which parts of the image are determined blobs and which are not.
  3. Running the blob tool (right-click the tool and choose run) will record the results for each blob. that can be viewed on the blob results property page
  4. .
  5. Use the up and down arrows on the blob results property page to view the statistics for each blob.  The blobs will be highlighted on the viewer window as they are selected on the results page.

Inputs

CIFViewer

The Viewer that displays the "Blobs"

Image

The input image.  CIF stands for "Common Image Format".  This is Automation Manager's native graphics format (like .jpg or .bmp).  

ROI

The Region of Interest by default this is the green rectangle that is placed on the screen when the tool is selected. Supports most ROI shapes including rotation.

CIFLUT

Common Image Format. Look up Table.

Blob Parameters

Auto Threshold

The threshold parameters can set manually or automatically. The user sets defines light and dark using the Lower and Upper Threshold values.

Lower Threshold
Upper Threshold

These will either be set by the "Auto Threshold" or by the user.  The  blob finder will locate any blobs between the upper and lower threshold.

Minimum Blob Size

The minimum number of pixels that determine a blob. All smaller areas are ignored.  This setting is useful to ignore pixelation around the central image.

  

On the first image the Minimum Blob Size is set too low so you end up with too many blobs to sort and too much complication.  By setting the minimum blob size to 100 you eliminate all the smaller blobs and isolate the central blob.

Remove Background Blobs

If checked, only the specified image in the blob is the focus; all background detail is ignored.

Remove Border Blobs

If checked, any blobs touching the edge of the ROI are ignored.

Sort Descending
If checked, the blobs are sorted in Descending order on the Sort Criteria.

Sort Criteria
The attribute to sort is selectable.

General

On the general tab the blob results can be setup to display in terms of :

Pixel/CIF
Reports in terms of the picture.

World
Reports in terms of the calibration.

Percent CIF
Reports in terms of a percentage of the picture.

Results


Number Blobs
The number of blobs found and measured.

Total Area
The combined area of all the blobs.

For each blob:

Area
Perimeter
Location
Number of holes/children
Foreground or background
Moments about each axis
Width
Height
Roundness 1 being round else < than 1
Squareness 1 being square else < than 1
Form factor Width/Height never exceeding 1

The number selection at the bottom shows the colors of each blob in terms of blue (1) green (2) and red (3).