# SortBlobs

SortBlobs is used to sort the blobs referenced in a Blobs data structure in relation to a fixture A fixture is a coordinate location on the image that keeps the tool in the place determined by the fixture..

## SortBlobs Overview

By computing the position of the referenced blob A blob is a group of pixels on the image that form a distinct pattern, typically used to represent objects, features, or areas of interest in object detection and segmentation tasks.'s center of mass (centroid) relative to the specified image fixture coordinate system, SortBlobs sorts the referenced blobs based upon one of their measurement characteristics, such as the distance along the x or y-axis, from a fixture origin or a grid, or the angle or angular distance of the blob.

Each blob in the referenced Blobs data structure is examined, and depending upon the Sort By parameter setting, the blob is identified and its position is calculated by measuring either the distance or angular relationship of the blob to a fixed location.

Once SortBlobs has sorted the referenced blobs, a new Blobs data structure and accompanying result table will be automatically inserted into the spreadsheet. The result table is sorted by how close the blob is to the chosen fixture, in descending order (the closest blob is listed first, the next closest second, and so on).

SortBlobs is an extremely helpful function Functions are tools that are available in Spreadsheet for processing and analyzing acquisitions or other results. You can add functions to your Spreadsheet job to create tool chains and produce results for specific applications. in instances where there are multiple blobs and the position of each blob in relation to the other blobs needs to be determined.

Inputs

The SortBlobs function has the following syntax:

SortBlobs(Blobs, Number to Sort, Sort By, Fixture, Show)

See the table for a description of the available parameters.

Parameter | Description
Blobs | This parameter uses Cell References to a spreadsheet cell containing the Blobs data structure that is to be sorted.
Number to Sort | Specifies the maximum number of blobs (1 to 4096; default = 3) to return. Note: If the value of this parameter is greater than zero, SortBlobs will automatically insert a result table containing a maximum of 10 entries that correspond to the first 10 blobs in the Blobs data structure. If you wish to display more entries, you can expand the table by copying the last row and pasting additional rows at the end. Make sure to increment the index number of any newly-pasted row so that the proper blob is indexed.
Sort By | Specifies how the referenced blobs will be measured and sorted.
0 = Y (default) | Sort by distance along the fixture y-coordinate, from small to large.
1 = X | Sort by distance along the fixture x-coordinate, from small to large.
2 = Angle | Sort by the angle (0 to 360 degrees), as measured counter-clockwise from the y-axis of the fixture coordinate system to the line segment defined by the blob's centroid (center of mass) and the fixture origin, from closest to furthest, in descending order.
3 = Angular Distance | Sort by the absolute value of the angle (-180 to 180 degrees), as measured from the x-axis of the fixture coordinate system to a line segment defined by the blob centroid and the fixture origin, from closest to furthest, in descending order.
4 = Distance | Sort by the distance from the fixture origin to the centroid of the blob, from closest to furthest, in descending order.
5 = Grid Y | Sort by distance along the y-coordinate of the fixture first, and then by distance along the x-coordinate, from closest to furthest, in descending order. Note: SortBlobs returns #ERR if Grid Y is selected and the function is referencing an image that was calibrated to world coordinate values, such as the output of a CalibrateImage or TransBlobsToWorld function. Grid Y sorting can only be applied to pixel coordinates.
6 = Grid X | Sort by distance along the x-coordinate of the fixture first, and then by distance along the y-axis, from closest to furthest, in descending order. Note: SortBlobs returns #ERR if Grid X is selected and the function is referencing an image that was calibrated to world coordinate values, such as the output of a CalibrateImage or TransBlobsToWorld function. Grid X sorting can only be applied to pixel coordinates.
7 = Width | Sorts by width values, from the largest to the smallest.
8 = Height | Sorts by height values, from the largest to the smallest.
Fixture | Defines the center of mass (centroid) of the referenced blob relative to a Fixture input or the output of the image coordinate system of a Vision Tools function. Setting the center of mass of the referenced blob relative to a Fixture ensures that if the Fixture is rotated or translated, the referenced blob will be rotated or translated in relation to the Fixture. The default setting is (0,0,0), the top leftmost corner of the image.
X | The X-offset, in image coordinates.
Y | The Y-offset, in image coordinates.
Theta | The rotation from the image X-axis, in the image coordinate system. (+/-360 degrees clockwise)
Show | Specifies the display mode for SortBlobs graphical overlays on top of the image.
0 = hide all (default) | All graphics will be hidden, except when the cell containing the SortBlobs function is highlighted in the spreadsheet.
1 = result graphics only | Blob outlines will be displayed at all times.

Outputs

Returns | A Blobs data structure containing the sorted blobs, or #ERR if any of the input parameters are invalid.
Results | When SortBlobs is initially inserted into a cell, a results table is created in the spreadsheet. Note: If the value of the Number to Sortparameter is greater than zero, SortBlobs automatically inserts a result table containing a maximum of 10 entries that correspond to the first 10 blobs in the Blobs data structure. If you wish to display more entries, you can expand the table by copying the last row and pasting additional rows at the end. Make sure to increment the index number of any newly-pasted row so that the proper blob is indexed. The following Blobs Vision Data Access functions are automatically inserted into the spreadsheet to create the SortBlobs data structure result table:
Label | Function Name | Description
Index |  | Index position of the blobs.
X | GetX(Blobs, Blob Index) | Returns the x-coordinate of the center of mass, or centroid, of a blob.
Y | GetY(Blobs, Blob Index) | Returns the y-coordinate of the center of mass, or centroid, of a blob.
Angle | GetAngle(Blobs, Blob Index) | Returns the angle of the principal, or major, axis of a blob with respect to the Y-axis.
Color | GetColor(Blobs, Blob Index) | Returns the color value of a blob: 0 = black 1 = white
Score | GetScore(Blobs, Blob Index) | A measure of how closely the blob matches the criteria of a FindBlobs function.
Area | GetArea(Blobs, Blob Index) | Returns the area of the blob, measured in pixels. Note: If the blob has holes, the Area value is different depending on whether you check the Fill Holes checkbox in the DetectBlobs function.
Elongation | GetElongation(Blobs, Blob Index) | Returns a value that represents how the pixels of a blob stretch out from the center of mass, or centroid. For example, a circle has an Elongation value close to zero, while a nail has a high Elongation value.
Holes | GetHoles(Blobs, Blob Index) | Returns the number of holes contained within the blob. Note: The function only returns holes whose area is greater than the Area Limit: Min value you give in the DetectBlobs function.
Perimeter | GetPerimeter(Blobs, Blob Index) | Returns the length of the boundary around the blob. The perimeter is calculated by counting the external edges of the pixels that form the boundary of the blob.
Spread | GetSpread(Blobs, Blob Index) | Returns a value that represents the distribution of pixels away from the center of mass, or centroid. For example, a circular shaped object has a lower Spread value than an oval shaped object.

See the Blobs Vision Data Access functions for details on the result table.