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Moments


Using the Blob Analysis module, you can also calculate the moments used to find the center of gravity, as well as other grayscale and binary moments. To calculate a moment of a specified order in X and Y (general moment), enable the M_MOMENT_GENERAL feature for calculation using MblobControl(); then specify the X and Y order of the moment to calculate using MblobControl() with M_MOMENT_GENERAL_ORDER_X and M_MOMENT_GENERAL_ORDER_Y, respectively. Select whether to calculate the ordinary or the central moment using MblobControl() with M_MOMENT_GENERAL_MODE. Central moments use coordinates that are relative to the center of gravity of the blob, and therefore are independent of a blob's position within the image; whereas, ordinary moments are affected by the blob position because they use coordinates relative to the top-left corner of the image. Use MblobGetResult() with M_MOMENT_GENERAL to retrieve the result.

You could alternatively enable the calculation of the M_MOMENT_FIRST_ORDER and/or M_MOMENT_SECOND_ORDER group of features for calculation using MblobControl(). These groups of features include only the more common moments (for example, MblobGetResult() with M_MOMENT_X0_Y1 or M_MOMENT_X0_Y2). These common moments are calculated faster than the general moment.