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Grassfire Thinning

The Grassfire effect is used to erode images by a set amount. When processing images a lot of small artifacts (erroneous pixels) can be present that create noise in the final results. Eroding the image can remove single pixels artifacts and smooth edges of larger objects.

As the Grassfire algorithm operates on a binary image you will need to specify a threshold value before eroding can begin. The Threshold histogram seen in the Grassfire interface will cause all pixels below the threshold to black and all pixels above the threshold to white. Note that the threshold operates only on intensity (grayscale) values. To segment color values use the RGB Threshold function and then the Grassfire threshold.

Below the threshold histogram is the erosion histogram. This histogram maps the object thickness on the X axis with the number of objects of that size on the Y axis. Moving the slider will cause all objects with thickness below that size to disappear and will shrink all larger objects by that amount. For example, if the slider is set to 10 then all objects will thickness (radius) less than 10 will disappear, all objects thicker than 10 pixels will be thinned (shrunk) by 10 pixels.

Interface

Instructions

1. Specify the intensity threshold cutoff
2. Specify the erosion depth. This is the amount of erosion that remaining objects will undergo.
3. If you want to create a mask out of the remaining objects select the "Create Mask" checkbox.

Example

SourceEroded Image

See Also


Erode
Threshold
Auto Threshold


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