Created
July 5, 2022 07:24
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| package draw | |
| import ( | |
| "image" | |
| "image/color" | |
| ) | |
| // ellipse defines the struct components required to apply the ellipse's formula. | |
| type ellipse struct { | |
| cx int // center x | |
| cy int // center y | |
| rx int // semi-major axis x | |
| ry int // semi-minor axis y | |
| } | |
| func NewEllipse(cx, cy, rx, ry int) *ellipse { | |
| return &ellipse{cx, cy, rx, ry} | |
| } | |
| func (e *ellipse) ColorModel() color.Model { | |
| return color.AlphaModel | |
| } | |
| func (e *ellipse) Bounds() image.Rectangle { | |
| min := image.Point{ | |
| X: e.cx - e.rx, | |
| Y: e.cy - e.ry, | |
| } | |
| max := image.Point{ | |
| X: e.cx + e.rx, | |
| Y: e.cy + e.ry, | |
| } | |
| return image.Rectangle{Min: min, Max: max} // size of just mask | |
| } | |
| func (e *ellipse) At(x, y int) color.Color { | |
| // Equation of ellipse | |
| p1 := float64((x-e.cx)*(x-e.cx)) / float64(e.rx*e.rx) | |
| p2 := float64((y-e.cy)*(y-e.cy)) / float64(e.ry*e.ry) | |
| eqn := p1 + p2 | |
| if eqn <= 1 { | |
| return color.Alpha{255} | |
| } | |
| return color.Alpha{0} | |
| } |
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