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04/27/2010

Super Blobber - New 4/17/01  DSB

The super blobber is a blob splitting agorithm for finding particles or objects that are brighter than their immediate surround, where the brightness of objects and background may very greatly over the image, and the objects can vary in size.

Note about holes:  The super blobber ignores holes in blobs.  The blobs are stored and reconstructed using their exterior outlines.

For blobbing, the red slider selects and colors red, all pixels in the image with intensities in the range denoted by the red band.  The blobber simply collects all of the red pixels into groups or blobs.  The pixels in the blobs are all 4-connected (i.e. pixels that touch only at the corners are not considered to be contiguous.)  Blobs smaller than the minimum area are rejected - area is the number of pixels. 

Note concerning non 8-bit images:  The blobber uses the scaled image and scaled threshold values - the intensity resolution of the blobber is thus 256 gray levels, and the blobs correspond to the red areas in the image.

 

Touch Edge?

For the blob function (not the superblob function), unless the touch edge parameter is 'yes', blobs that touch the edge of the image (actually that come within one pixel of the edge of the image) are rejected.  Since the super blobber usually starts with a very low threshold so that most or all of the image is selected, it always allows blobs to touch the edge of the image.  These edge touchers can be rejected at a later processing stage.

 

Area and Filled Area

If a blob has holes, the area will be less than the filled area.  Superblobs are stored by their outlines only, so information on  holes is lost.  At moment, 6/21/2001, the area (with any holes)  is not reconstructed - the filled area is substituted for it.

Super blobbing

The suber blobber blobs an image many times, each time with a larger lower threshold.  Raising of the lower threshold in effect removes some pixels from the blobs, making them smaller, and in some cases, splitting them into two or more daugher blobs. The super blobber keeps all of the blobs from the initial threshold, even though they may erode away to nothing at higher thresholds, UNLESS they split into daughter blobs.  In this case, it replaces the original blob with its daughters, and continues the process. The threshold slider can be used to set the minimum threshold above the background noise.  The super blobber splits what is left into blobs.