Sinc Based Interpolation

Figure 20 shows the result of using two different truncated and apodized approximations of sinc, where the support is the same as in the functions of Fig. 19. The test image of Fig. 17 has been built with a nonnull average; since an apodized version of sinc does not reproduce this constant value faithfully, each incremental rotation results in a small drift of the average value of the image. This would be true of any interpolation function that would not satisfy the partition of unity. This drift manifests itself as images that appear too dark or too light. We conclude that sinc performs poorly when compared to other synthesis functions of the same support, and not only drift of the mean value, but also both blocking and excessive blurring artifacts are present.

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