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