231 lines
6.7 KiB
Go
231 lines
6.7 KiB
Go
package shapes
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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/canvas"
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// FillEllipse draws the content of one canvas onto another, clipped by an
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// ellipse stretched to the bounds of the source canvas. The offset point
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// defines where the origin point of the source canvas is positioned in relation
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// to the origin point of the destination canvas. To prevent the entire source
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// canvas's bounds from being used, it must be cut with canvas.Cut().
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func FillEllipse (
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destination canvas.Canvas,
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source canvas.Canvas,
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offset image.Point,
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) (
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updatedRegion image.Rectangle,
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) {
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dstData, dstStride := destination.Buffer()
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srcData, srcStride := source.Buffer()
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bounds := source.Bounds().Intersect(destination.Bounds()).Canon()
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realBounds := source.Bounds()
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if bounds.Empty() { return }
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updatedRegion = bounds
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point := image.Point { }
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for point.Y = bounds.Min.Y; point.Y < bounds.Max.Y; point.Y ++ {
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for point.X = bounds.Min.X; point.X < bounds.Max.X; point.X ++ {
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if inEllipse(point, realBounds) {
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offsetPoint := point.Add(offset)
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dstIndex := offsetPoint.X + (offsetPoint.Y) * dstStride
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srcIndex := point.X + point.Y * srcStride
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dstData[dstIndex] = srcData[srcIndex]
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}
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}}
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return
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}
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// StrokeEllipse is similar to FillEllipse, but it draws an elliptical inset
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// outline of the source canvas onto the destination canvas. To prevent the
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// entire source canvas's bounds from being used, it must be cut with
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// canvas.Cut().
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func StrokeEllipse (
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destination canvas.Canvas,
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source canvas.Canvas,
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offset image.Point,
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weight int,
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) {
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if weight < 1 { return }
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dstData, dstStride := destination.Buffer()
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srcData, srcStride := source.Buffer()
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bounds := source.Bounds().Inset(weight - 1)
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context := ellipsePlottingContext {
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plottingContext: plottingContext {
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dstData: dstData,
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dstStride: dstStride,
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srcData: srcData,
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srcStride: srcStride,
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weight: weight,
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offset: offset,
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bounds: bounds.Intersect(destination.Bounds()),
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},
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radii: image.Pt(bounds.Dx() / 2 - 1, bounds.Dy() / 2 - 1),
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}
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context.center = bounds.Min.Add(context.radii)
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context.plotEllipse()
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}
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type ellipsePlottingContext struct {
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plottingContext
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radii image.Point
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center image.Point
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}
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func (context ellipsePlottingContext) plotEllipse () {
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x := float64(0)
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y := float64(context.radii.Y)
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// region 1 decision parameter
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decision1 :=
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float64(context.radii.Y * context.radii.Y) -
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float64(context.radii.X * context.radii.X * context.radii.Y) +
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(0.25 * float64(context.radii.X) * float64(context.radii.X))
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decisionX := float64(2 * context.radii.Y * context.radii.Y * int(x))
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decisionY := float64(2 * context.radii.X * context.radii.X * int(y))
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// draw region 1
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for decisionX < decisionY {
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points := []image.Point {
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image.Pt(-int(x) + context.center.X, -int(y) + context.center.Y),
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image.Pt( int(x) + context.center.X, -int(y) + context.center.Y),
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image.Pt(-int(x) + context.center.X, int(y) + context.center.Y),
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image.Pt( int(x) + context.center.X, int(y) + context.center.Y),
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}
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if context.srcData == nil {
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context.plotColor(points[0])
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context.plotColor(points[1])
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context.plotColor(points[2])
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context.plotColor(points[3])
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} else {
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context.plotSource(points[0])
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context.plotSource(points[1])
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context.plotSource(points[2])
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context.plotSource(points[3])
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}
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if (decision1 < 0) {
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x ++
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decisionX += float64(2 * context.radii.Y * context.radii.Y)
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decision1 += decisionX + float64(context.radii.Y * context.radii.Y)
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} else {
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x ++
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y --
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decisionX += float64(2 * context.radii.Y * context.radii.Y)
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decisionY -= float64(2 * context.radii.X * context.radii.X)
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decision1 +=
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decisionX - decisionY +
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float64(context.radii.Y * context.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(context.radii.Y * context.radii.Y) * (x + 0.5) * (x + 0.5) +
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float64(context.radii.X * context.radii.X) * (y - 1) * (y - 1) -
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float64(context.radii.X * context.radii.X * context.radii.Y * context.radii.Y)
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// draw region 2
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for y >= 0 {
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points := []image.Point {
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image.Pt( int(x) + context.center.X, int(y) + context.center.Y),
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image.Pt(-int(x) + context.center.X, int(y) + context.center.Y),
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image.Pt( int(x) + context.center.X, -int(y) + context.center.Y),
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image.Pt(-int(x) + context.center.X, -int(y) + context.center.Y),
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}
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if context.srcData == nil {
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context.plotColor(points[0])
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context.plotColor(points[1])
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context.plotColor(points[2])
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context.plotColor(points[3])
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} else {
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context.plotSource(points[0])
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context.plotSource(points[1])
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context.plotSource(points[2])
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context.plotSource(points[3])
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}
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if decision2 > 0 {
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y --
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decisionY -= float64(2 * context.radii.X * context.radii.X)
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decision2 += float64(context.radii.X * context.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 * context.radii.Y * context.radii.Y)
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decisionY -= float64(2 * context.radii.X * context.radii.X)
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decision2 +=
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decisionX - decisionY +
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float64(context.radii.X * context.radii.X)
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}
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}
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}
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// FillColorEllipse fills an ellipse within the destination canvas with a solid
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// color.
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func FillColorEllipse (
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destination canvas.Canvas,
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color color.RGBA,
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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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dstData, dstStride := destination.Buffer()
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realBounds := bounds
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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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point := image.Point { }
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for point.Y = bounds.Min.Y; point.Y < bounds.Max.Y; point.Y ++ {
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for point.X = bounds.Min.X; point.X < bounds.Max.X; point.X ++ {
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if inEllipse(point, realBounds) {
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dstData[point.X + point.Y * dstStride] = color
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}
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}}
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return
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}
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// StrokeColorEllipse is similar to FillColorEllipse, but it draws an inset
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// outline of an ellipse instead.
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func StrokeColorEllipse (
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destination canvas.Canvas,
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color color.RGBA,
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bounds image.Rectangle,
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weight int,
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) (
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updatedRegion image.Rectangle,
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) {
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if weight < 1 { return }
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dstData, dstStride := destination.Buffer()
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bounds = bounds.Inset(weight - 1)
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context := ellipsePlottingContext {
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plottingContext: plottingContext {
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dstData: dstData,
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dstStride: dstStride,
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color: color,
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weight: weight,
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bounds: bounds.Intersect(destination.Bounds()),
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},
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radii: image.Pt(bounds.Dx() / 2 - 1, bounds.Dy() / 2 - 1),
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}
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context.center = bounds.Min.Add(context.radii)
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context.plotEllipse()
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return
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}
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func inEllipse (point image.Point, bounds image.Rectangle) bool {
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point = point.Sub(bounds.Min)
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x := (float64(point.X) + 0.5) / float64(bounds.Dx()) - 0.5
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y := (float64(point.Y) + 0.5) / float64(bounds.Dy()) - 0.5
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return math.Hypot(x, y) <= 0.5
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}
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