Objective The measurement accuracy and efficiency of traditional seed investigation methods could not meet the needs of modern rice breeding research. A synchronous collection device of rice grain image and quality information was designed to automatically extract rice seed investigation parameters.

Method The image of grain region was automatically extracted by mask method, and the total number of rice grains was obtained according to the law between rice projection area and rice quantity. Empty grains were identified according to the difference of the hull contour between empty grains and full grains. Based on the mean value calibration method of corner spacing, the grain length and width were obtained by combining the minimum circumscribed rectangle method of contour, and the grain perimeter was obtained by combining the chain code method. The square area mean calibration method and pixel accumulation method were used to obtain the grain area. The effects of camera height, grain quantity, grain type and regular graph type on the extraction accuracy of grain character parameters were analyzed.

Result The camera height had a obvious impact on the measurement accuracies of total number, empty number, length and width of rice grains, the grain type had a obvious impact on the measurement accuracy of width, and the regular graph type had a obvious impact on the measurement accuracies of grain area and perimeter. The determination coefficients (R²) of total grain number, empty grain number, grain length, grain width, grain perimeter and grain area measured by the proposed method were 0.99830, 0.98780, 0.99610, 0.78290, 0.99510 and 0.99998 respectively, the average measurement accuracies were 99.47%, 87.17%, 96.55%, 96.36%, 98.00% and 95.86% respectively, and the measurement efficiency was 16.52 grains per second.

Conclusion The automatic extraction method of rice seed investigation parameters used in this paper is feasible, and can provide technical references for the development of automatic seed investigation machine.