CanvasGradient createCircularGradient(float centerX, float centerY, float endRadius)
         A gradient from 0 at radius 0 to 1 at radius `endRadius`

    CanvasGradient createEllipticalGradient(float x0, float y0, float x1, float y1, float r2)
         An elliptical gradient from 0 at radius 0 to 1 at radiuses given by (x1, y1) and r2