// non-bressenham line
// TODO: figure out just how much better bressenham is
func line(dst *sdl.Surface, p0, p1 Point, c image.Color) {
d := p1.Sub(p0)
l := d.ToFloat().Length()
inc := int32(1)
if d.X*d.X > d.Y*d.Y {
if d.X < 0 {
inc = -1
}
m := d.ToFloat().Mult(1.0 / l).Slope()
for x := int32(0); x != d.X; x += inc {
y := int32(m * float64(x))
dst.Set(int(x+p0.X), int(y+p0.Y), c)
}
} else {
if d.Y < 0 {
inc = -1
}
m := d.ToFloat().Inverse().Mult(1.0 / l).Slope()
for y := int32(0); y != d.Y; y += inc {
x := int32(m * float64(y))
dst.Set(int(x+p0.X), int(y+p0.Y), c)
}
}
}
func filledCircle(dst *sdl.Surface, org Point, r int) {
colour := image.RGBAColor{0, 255, 0, 255}
// add a bias for smoother poles
br := float64(r) + 0.5
for x := -r; x <= r; x++ {
dy := int(math.Sqrt(br*br - float64(x*x)))
for y := -dy; y <= dy; y++ {
dst.Set(int(org.X)+x, int(org.Y)+y, colour)
}
}
}
func filledEllipse(dst *sdl.Surface, org Point, a, b int) {
colour := image.RGBAColor{0, 255, 0, 255}
// add a bias to a and b for smoother poles
ba := float64(a) + 0.5
bb := float64(b) + 0.5
for x := -a; x <= a; x++ {
dy := int(math.Sqrt((bb * bb) * (1.0 - float64(x*x)/(ba*ba))))
for y := -dy; y <= dy; y++ {
dst.Set(int(org.X)+x, int(org.Y)+y, colour)
}
}
}
func circle(dst *sdl.Surface, org Point, r int) {
colour := image.RGBAColor{0, 255, 255, 0}
// set the poles
dst.Set(int(org.X), int(org.Y)+r, colour)
dst.Set(int(org.X), int(org.Y)-r, colour)
dst.Set(int(org.X)+r, int(org.Y), colour)
dst.Set(int(org.X)-r, int(org.Y), colour)
// add a bias for smoother poles
br := float64(r) + 0.5
// draw and rotate an octant
var x int32 = 1
for {
y := int32(math.Sqrt(br*br - float64(x*x)))
if x < y {
dst.Set(int(org.X+x), int(org.Y+y), colour)
dst.Set(int(org.X-x), int(org.Y+y), colour)
dst.Set(int(org.X+x), int(org.Y-y), colour)
dst.Set(int(org.X-x), int(org.Y-y), colour)
dst.Set(int(org.X+y), int(org.Y+x), colour)
dst.Set(int(org.X-y), int(org.Y+x), colour)
dst.Set(int(org.X+y), int(org.Y-x), colour)
dst.Set(int(org.X-y), int(org.Y-x), colour)
} else {
if x == y {
// draw the NE, SE, SW, and NW pixels
dst.Set(int(org.X+x), int(org.Y+y), colour)
dst.Set(int(org.X-x), int(org.Y+y), colour)
dst.Set(int(org.X+x), int(org.Y-y), colour)
dst.Set(int(org.X-x), int(org.Y-y), colour)
}
break
}
x++
}
}
func ellipse(dst *sdl.Surface, org Point, a, b int) {
colour := image.RGBAColor{0, 255, 0, 255}
// set the poles
dst.Set(int(org.X), int(org.Y)+b, colour)
dst.Set(int(org.X), int(org.Y)-b, colour)
dst.Set(int(org.X)+a, int(org.Y), colour)
dst.Set(int(org.X)-a, int(org.Y), colour)
// add a bias to a and b for smoother poles
ba := float64(a) + 0.5
bb := float64(b) + 0.5
// draw and rotate a quadrant
for x := 1; x < a; x++ {
y1 := (-bb * float64(x)) / (ba * math.Sqrt(ba*ba-float64(x*x)))
y := int(math.Sqrt((bb * bb) * (1.0 - float64(x*x)/(ba*ba))))
if y1 > -1.0 {
dst.Set(int(org.X)+x, int(org.Y)+y, colour)
dst.Set(int(org.X)-x, int(org.Y)+y, colour)
dst.Set(int(org.X)+x, int(org.Y)-y, colour)
dst.Set(int(org.X)-x, int(org.Y)-y, colour)
} else {
for dy := 1; dy <= y; dy++ {
dx := int(math.Sqrt((ba * ba) * (1.0 - float64(dy*dy)/(bb*bb))))
dst.Set(int(org.X)+dx, int(org.Y)+dy, colour)
dst.Set(int(org.X)-dx, int(org.Y)+dy, colour)
dst.Set(int(org.X)+dx, int(org.Y)-dy, colour)
dst.Set(int(org.X)-dx, int(org.Y)-dy, colour)
}
break
}
}
}