Off-image detection circuit for an image analyzer

An image analyzer system having at least one neighborhood transformation stage for analyzing image information contained in serial scan lines of pixels, some of the pixels having valid data values representing image information while other pixels have invalid data values not representing characteristics of the image to be analyzed, said system comprising:

• a data bus for transferring the pixels to the stage;
• a control line coupled to the stage and adapted to provide signals indicating whether valid or invalid pixels are being transferred over the bus to the stage;
• neighborhood extraction means coupled to the bus for temporarily storing a group of neighboring pixels;
• off image detector means coupled to said control line, operative to utilize the signals thereon to generate an output when invalid pixels are stored in the neighborhood extraction means;
• and
• transformation logic means for generating a transformation output for the stage as a function of the pixel values stored in the neighborhood extraction means and the output from the off image detector means.

A method of analyzing image information contained in a plurality of scan lines of pixel values, some lines having valid pixels therein representing characteristics of the image to be analyzed together with invalid pixels not representing image information, said method comprising:

• storing the number of valid pixels in at least two successive scan lines;
• counting the number of valid pixels in the next scan line;
• comparing the contents of the stored numbers with each incremented count of valid pixels in the next scan line;
• selectively generating off image signals as a function of the comparison;
• loading an array of storage devices with a neighborhood of pixel values;
• modifying the pixel values contained in selected storage devices with a predetermined value in response to said off image signals;
• and
• generating a transformation output signal as a function of the contents of the storage devices as modified by said predetermined value.

In an image analyzer system having a neighborhood transformation stage for analyzing image information contained in serial scan lines of pixels, some of the pixels having valid data values representing characteristics of the image to be analyzed while other pixels have invalid data values not representing image information, wherein the improvement comprises:

• a data bus for transferring the pixels to the stage;
• a control line coupled to the stage and adapted to provide signals indicating whether valid or invalid pixels are being transferred over the bus to the stage;
• neighborhood extraction means coupled to the bus for temporarily storing a group of neighboring pixels;
• maximum value detector means for comparing values of neighboring pixels stored in the neighborhood extraction means and selecting the maximum value thereof;
• and
• off-image detector means coupled to said control line, operative to utilize the signals thereon to detect when invalid pixels are stored in the neighborhood extraction means and provide an output for causing the maximum value detector means to ignore the values of the identified invalid pixels in its selection of the maximum value of the neighboring pixel values.