package artist import "math" import "image" import "image/color" import "git.tebibyte.media/sashakoshka/tomo/canvas" // FillEllipse draws a filled ellipse with the specified pattern. func FillEllipse ( destination canvas.Canvas, source Pattern, bounds image.Rectangle, ) ( updatedRegion image.Rectangle, ) { bounds = bounds.Canon() data, stride := destination.Buffer() realWidth, realHeight := bounds.Dx(), bounds.Dy() bounds = bounds.Intersect(destination.Bounds()).Canon() if bounds.Empty() { return } updatedRegion = bounds width, height := bounds.Dx(), bounds.Dy() for y := 0; y < height; y ++ { for x := 0; x < width; x ++ { xf := (float64(x) + 0.5) / float64(realWidth) - 0.5 yf := (float64(y) + 0.5) / float64(realHeight) - 0.5 if math.Sqrt(xf * xf + yf * yf) <= 0.5 { data[x + bounds.Min.X + (y + bounds.Min.Y) * stride] = source.AtWhen(x, y, realWidth, realHeight) } }} return } // StrokeEllipse draws the outline of an ellipse with the specified line weight // and pattern. func StrokeEllipse ( destination canvas.Canvas, source Pattern, weight int, bounds image.Rectangle, ) { if weight < 1 { return } data, stride := destination.Buffer() bounds = bounds.Canon().Inset(weight - 1) width, height := bounds.Dx(), bounds.Dy() context := ellipsePlottingContext { data: data, stride: stride, source: source, width: width, height: height, weight: weight, bounds: bounds, } bounds.Max.X -= 1 bounds.Max.Y -= 1 radii := image.Pt ( bounds.Dx() / 2, bounds.Dy() / 2) center := bounds.Min.Add(radii) x := float64(0) y := float64(radii.Y) // region 1 decision parameter decision1 := float64(radii.Y * radii.Y) - float64(radii.X * radii.X * radii.Y) + (0.25 * float64(radii.X) * float64(radii.X)) decisionX := float64(2 * radii.Y * radii.Y * int(x)) decisionY := float64(2 * radii.X * radii.X * int(y)) // draw region 1 for decisionX < decisionY { context.plot( int(x) + center.X, int(y) + center.Y) context.plot(-int(x) + center.X, int(y) + center.Y) context.plot( int(x) + center.X, -int(y) + center.Y) context.plot(-int(x) + center.X, -int(y) + center.Y) if (decision1 < 0) { x ++ decisionX += float64(2 * radii.Y * radii.Y) decision1 += decisionX + float64(radii.Y * radii.Y) } else { x ++ y -- decisionX += float64(2 * radii.Y * radii.Y) decisionY -= float64(2 * radii.X * radii.X) decision1 += decisionX - decisionY + float64(radii.Y * radii.Y) } } // region 2 decision parameter decision2 := float64(radii.Y * radii.Y) * (x + 0.5) * (x + 0.5) + float64(radii.X * radii.X) * (y - 1) * (y - 1) - float64(radii.X * radii.X * radii.Y * radii.Y) // draw region 2 for y >= 0 { context.plot( int(x) + center.X, int(y) + center.Y) context.plot(-int(x) + center.X, int(y) + center.Y) context.plot( int(x) + center.X, -int(y) + center.Y) context.plot(-int(x) + center.X, -int(y) + center.Y) if decision2 > 0 { y -- decisionY -= float64(2 * radii.X * radii.X) decision2 += float64(radii.X * radii.X) - decisionY } else { y -- x ++ decisionX += float64(2 * radii.Y * radii.Y) decisionY -= float64(2 * radii.X * radii.X) decision2 += decisionX - decisionY + float64(radii.X * radii.X) } } } type ellipsePlottingContext struct { data []color.RGBA stride int source Pattern width, height int weight int bounds image.Rectangle } func (context ellipsePlottingContext) plot (x, y int) { if (image.Point { x, y }).In(context.bounds) { squareAround ( context.data, context.stride, context.source, x, y, context.width, context.height, context.weight) } }