To create Threshold effect, click Image | Threshold or select Threshold folder.
Choose the value in the Value scroll boxes.
Choose the Anti-Aliasing effect if you wish to smooth the edges.
By choosing the Value you determine the Threshold. If the value of one of the RGB parts of the color
is bigger than the value of the Threshold, then it transforms to a value of 255. If it less than the value
of the threshold, it transforms the value to 0.
That means that the hue ( red, green or blue) will transform into the pure color.