Fast image processing techniques for the gill position measurement in fish

Fast and accurate measurement of gill position is important in automated fish processing, to ensure correct positioning in a cutting machine. Two image-processing techniques for accomplishing this are presented. The methods are based on the isolation and enhancement of an elongated edge-like structure in the image of the head area of a fish. In one approach, the gill position is measured by establishing the smallest rectangle that encloses this structure. In the other, the particular image is transformed into a condensed signature through gray-level averaging in the direction of the edge-like structure. Associated image generation, enhancement, and processing procedures are described. The techniques are implemented on a vision workstation containing a multitasking operating system with a real-time kernel, and are tested on Pacific salmon