rotate:
matrix(cosθ,sinθ,-sinθ,cosθ,0,0) x' = x*cosθ-y*sinθ+0 = x*cosθ-y*sinθ y' = x*sinθ+y*cosθ+0 = x*sinθ+y*cosθ
skew:
matrix(1,tan(θy),tan(θx),1,0,0) x' = x+y*tan(θx)+0 = x+y*tan(θx) y' = x*tan(θy)+y+0 = x*tan(θy)+y
对称
a = (1-k*k)/(k*k+1); b = 2k/(k*k+1); c = 2k/(k*k+1); d = (k*k-1)/(k*k+1);