Method and means of least squares designed filters for image segmentation in scanning cytometry

A method executable on a computer for separating an object from a background in a pixelated image with a best-designed digital filter, the method comprising:

• defining a type of digital filter, the digital filter including a neighborhood operator of second or higher order for processing neighborhoods of pixels in a pixel array;
• setting a contrast range (R,Q) in which R<Q;
• receiving a first pixel array defining a pixelated image including one or more objects and a background;
• applying the digital filter to the first pixel array to create a first filtered image;
• receiving a second pixel array defining a reference image, the reference image including at least one object included in the pixelated image and a background, in which pixels included in the at least one object are distinguished from pixels included in the background by a predetermined amount of contrast;
• determining a merit function value by:
• setting the merit function value to a specified value if, either a pixel in the background of the pixelated image is less than or equal to R and a corresponding pixel in the reference image is in a background of the reference image, or a pixel in an object of the pixelated image is greater than or equal to Q and a
• corresponding pixel in the reference image is in an object of the reference image;
• or,
• calculating a minimum merit function value otherwise;
• computing values of neighborhood operator elements in response to the merit function value;
• receiving a third pixel array defining an image including one or more objects and a background;
• applying the digital filter to the third pixel array to create a second filtered image;
• and
• creating a segmented image in which an object of the image is separated from the background in the image by thresholding the second filtered image.

An image segmentation system, comprising:

• means for acquiring an array of pixels defining a pixelated image including one or more objects and a background;
• a digital filter for producing a transformed array of pixels representing the transformation of a pixelated image, the digital filter including a neighborhood operator of second or higher order for processing intensities of pixels in a pixel array;
• means coupled to the means for acquiring and to the digital filter for setting values of the neighborhood operator in response to a first pixel array defining a pixelated image including one or more objects and a background and a second pixel array defining a reference image, the reference image including at least one object included in the pixelated image and a background in which pixels included in the at least one object are distinguished from pixels included in the background by a predetermined amount of contrast;
• means for determining a merit function value by:
• the pixel in the background of the pixelated image is less than or equal to R and the corresponding pixel in the reference image has a magnitude equal to a predetermined background value, or the pixel in the object of the pixelated image is greater than or equal to Q and the corresponding pixel in the reference image has a magnitude equal to a predetermined object value;
• or
• calculating a positive, non-zero merit function value otherwise;
• means for changing the neighborhood operator to a new neighborhood operator in response to a minimum merit function value;
• and
• means for applying the new neighborhood operator of the digital filter to a third array of pixels defining an image to be segmented, the image to be segmented including one or more objects and a background, such that the new neighborhood operator creates or enhances contrast between the one or more objects in the background.