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tomo-old/artist/shapes/ellipse.go

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