An Accurate Affine Registration Method for Appearance Phenotype Measurement Based on Distance Reference and Camera Attitude Parameters

Accurate registration is a key step for precise and real-time measurement of appearance phenotype using the forward intersection method. For example, in order to reconstruct the details of the plant organs (leaf, fruit, stem, etc.), precisely matched image points from varied object points should be of high density in the image region of a target organ in each image. However, this task is not achieved stably with relevant methods in current literature. In this paper, the multiple basic parameters for affine registration are obtained by estimating the distance reference value, obtaining the camera attitude from the inertial module, calibrating the internal parameters of the camera, calibrating the structure parameters of the vision system, aberration modelling, and other methods. The basic parameters are used to express the vectors of object points to be measured, the optical vectors of the image points to be matched and the scale factors of the optical projection in varied camera coordinate systems. In the registration process, these vectors are affine operated to map the first target image point to each image via the strategy of mapping. The system error of the approximately matched pixel is eliminated in the micro-region of error centred around the approximately matched pixel. Research shows that this affine registration algorithm is able to obtain a large number of highdensity and accurate matched image points that correspond to different target points in the leaf region of each image. This is suitable for forward intersection measurement of the plant appearance phenotype details with a real-time vision system based on our results. The proposed registration method is highly robust, efficient and precise; and requires relatively little computation resources.