Splay correction for local regression/smoothing of pair-rule gene expression patterns. (A) Red channel of image of embryo FEScc01 (fushi-tarazu gene). (B) Mean intensity as a function of anterior–posterior position. (C) Simulated embryo image after splay correction. (D) Mean intensity after correction. Parameters of the coordinate transform are chosen to maximize the variance, along the anterior–posterior axis, of mean intensity.