Effect of window size and threshold value on production of low-entropy regions. (A) Input image. Low-entropy regions were produced from an image of a four-cell-stage embryo using various window sizes and threshold values. (B–D) Effect of window size on image conversion using local image entropy. The input image was applied to the image conversion using window sizes of 4 × 4 (B), 10 × 10 (C), and 50 × 50 (D) pixels. Darker colors represent lower local image entropies. (E–M) Effect of window size and threshold value on low-entropy regions. Low-entropy regions (black) were produced using threshold values of 200 (E, H, K), 175 (F, I, L), or 150 (G, J, M) from the images resulting from the image conversion, using window sizes of 4 × 4 (E–G), 10 × 10 (H–J) or 50 × 50 (K–M) pixels. A window of 10 × 10 pixels corresponds to that of 1 μm × 1 μm.