Hideyo Yokotsuka

Comparison of Image Interpolation Methods Applied to Least Squares Matching

Least squares matching requires appropriate interpolation of the gray values in the search window corresponding to a template. This paper reports an experiment conducted to evaluate image interpolation methods on matching accuracy of least squares matching by using 54 diverse images. Three popular methods in photogrammetry: bilinear interpolation [BL], cubic convolution by Riffman [C1], and cubic convolution by Simon [C2] were investigated. The results demonstrate that [C2] can produce better matching results than [BL] and [C1] in most cases when an image has no noise or smaller noises. Meanwhile, the results demonstrate that there is nothing to choose among three interpolation methods when an image has larger noises. Since the differences of the matching accuracy among three methods were small enough to be neglected, we conclude that [BL] would be the best interpolation method applied to least squares matching in most cases considering its inexpensive computational cost.

Measurement accuracy of center location of a circle by centroid method

This paper reports an investigation of the effect of digitization on the measurement accuracy of the center location of a circle by a centroid method. Although general expressions representing the measurement accuracy of the center location of a circle by the centroid method are unable to be obtained analytically, we have succeeded in obtaining the variances V of measurement errors for 39 quantization bits n ranging from one to infinity by numerical integration. We have succeeded in obtaining the effective approximation formulae of V as a function of the diameter d of the circle for any n as well. The results show that V would oscillate on an approximate one-pixel cycle in d for any n and decrease as n increases. The differences of V among the different n would be negligible when n ≥ 6. Some behaviors of V with an increase in n are demonstrated.

A MOS circuit for a nonmonotonic neural network with excellent retrieval capabilities

An MOS circuit is proposed for implementing a nonmonotonic transfer characteristic of a neural network. The present research is motivated by the recent results of theoretical studies showing excellent equilibrium properties of networks with the nonmonotonic neural units. These properties include enhancement of storage capacity and complete elimination of noise in associative memory recall. The simple form of the transfer characteristic enables one to implement it with a simple electrical circuit of standard MOS transistors. SPICE simulation results are shown for the behavior of the neural units in associative memory recall.

Comparison on accuracy of image matching between lossy JPEG compression and lossy JPEG 2000 compression

This paper reports an experiment conducted in order to compare lossy JPEG compression and lossy JPEG 2000 compression on the accuracy of image matching. The experiment has been conducted by using 54 color images of diverse textures and diverse tones of color on the assumption that image matching utilizes a pair of images reconstructed from image data which are lossily compressed in an ordinary digital camera. Lossy JPEG compression has been executed with a set of compression parameters utilized in a digital camera Canon EOS 20D, while lossy JPEG 2000 compression has been executed in the way as the file size of a piece of JPEG 2000 compressed image data is the same file size of the corresponding JPEG compressed image data. Moreover, we have prepared another set of JPEG and JPEG 2000 compressed image data which are lossily compressed with the compression ratio expected for an ordinary color image when it is compressed in the EOS 20D. When the file size of a piece of JPEG 2000 compressed image data is the same as that of a piece of JPEG compressed image data, the experiment results clearly show that the compression performance of JPEG 2000 compression would be superior to that of JPEG compression on image quality as to pixel value in RGB color space. On the contrary, the results do not necessarily indicate that JPEG 2000 compression would be able to provide more accurate matching results than JPEG compression.