This function performs a simple pattern recognition on the image to identify features that resemble dark circular spots. It creates a new 8-bit grayscale image that represents where the spots are located in the original image. The background where no spots are recognized is set to white. The darkness of the spot is related to the size and density of the original spot. However, the relationship is not linear because large spots in the original image may be identified as part of the background. The image should be converted to grayscale before starting.
Checking "use contrast filter" will cause your image to be filtered using a "maximum local contrast" filter. This will increase the number of spots that are recognized and helps to separate overlapping spots. This may take up to one minute or longer depending on the size of the original image.
Increasing the maximum spot radius will enable the recognition algorithm to identify larger spots. The length of time required to search the image for spots increases with the square of the maximum spot radius. For most images, this parameter should be left at "2".
This function is particularly useful in analysis of 2-D protein gels, where many faint spots are frequently superimposed, making analysis of the gel tedious. The image below shows a section of a 2D gel before processing (left), after spot enhancement without the contrast filter (center), and after enhancement with the filter (right).
Enhancing spots in a 2D gel.