Lemon-shaped Ellipse Tool (WIP)
* Add initial Ellipse Tool to the Editor Mode. Currently there's something wrong with the algorithm and the ellipses have a sort of 'lemon shape' to them. * Refactor the IterLine/IterLine2 functions to be more consistent. IterLine used to be the raw algorithm that took a bunch of coordinate numbers and IterLine2 took two render.Point's and was the main one used throughout the app. Now, IterLine takes the two Points and the raw algorithm function removed.
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@ -44,7 +44,7 @@ func (e *Engine) DrawPoint(color render.Color, point render.Point) {
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// DrawLine draws a line between two points.
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func (e *Engine) DrawLine(color render.Color, a, b render.Point) {
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e.canvas.ctx2d.Set("fillStyle", RGBA(color))
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for pt := range render.IterLine2(a, b) {
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for pt := range render.IterLine(a, b) {
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e.canvas.ctx2d.Call("fillRect",
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int(pt.X),
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int(pt.Y),
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87
interface.go
87
interface.go
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@ -3,7 +3,6 @@ package render
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import (
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"fmt"
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"image"
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"math"
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"git.kirsle.net/apps/doodle/lib/events"
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)
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@ -195,89 +194,3 @@ var (
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Purple = RGBA(153, 0, 153, 255)
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Pink = RGBA(255, 153, 255, 255)
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)
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// IterLine is a generator that returns the X,Y coordinates to draw a line.
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// https://en.wikipedia.org/wiki/Digital_differential_analyzer_(graphics_algorithm)
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func IterLine(x1, y1, x2, y2 int32) chan Point {
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generator := make(chan Point)
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go func() {
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var (
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dx = float64(x2 - x1)
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dy = float64(y2 - y1)
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)
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var step float64
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if math.Abs(dx) >= math.Abs(dy) {
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step = math.Abs(dx)
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} else {
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step = math.Abs(dy)
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}
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dx = dx / step
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dy = dy / step
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x := float64(x1)
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y := float64(y1)
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for i := 0; i <= int(step); i++ {
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generator <- Point{
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X: int32(x),
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Y: int32(y),
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}
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x += dx
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y += dy
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}
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close(generator)
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}()
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return generator
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}
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// IterLine2 works with two Points rather than four coordinates.
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func IterLine2(p1 Point, p2 Point) chan Point {
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return IterLine(p1.X, p1.Y, p2.X, p2.Y)
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}
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// IterRect loops through all the points forming a rectangle between the
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// top-left point and the bottom-right point.
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func IterRect(p1, p2 Point) chan Point {
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generator := make(chan Point)
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go func() {
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var (
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TopLeft = p1
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BottomRight = p2
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TopRight = Point{
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X: BottomRight.X,
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Y: TopLeft.Y,
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}
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BottomLeft = Point{
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X: TopLeft.X,
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Y: BottomRight.Y,
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}
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dedupe = map[Point]interface{}{}
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)
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// Trace all four edges and yield it.
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var edges = []struct {
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A Point
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B Point
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}{
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{TopLeft, TopRight},
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{TopLeft, BottomLeft},
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{BottomLeft, BottomRight},
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{TopRight, BottomRight},
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}
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for _, edge := range edges {
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for pt := range IterLine2(edge.A, edge.B) {
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if _, ok := dedupe[pt]; !ok {
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generator <- pt
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dedupe[pt] = nil
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}
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}
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}
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close(generator)
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}()
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return generator
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}
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198
shapes.go
Normal file
198
shapes.go
Normal file
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@ -0,0 +1,198 @@
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package render
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import (
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"math"
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"git.kirsle.net/apps/doodle/pkg/log"
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)
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// IterLine is a generator that returns the X,Y coordinates to draw a line.
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// https://en.wikipedia.org/wiki/Digital_differential_analyzer_(graphics_algorithm)
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func IterLine(p1 Point, p2 Point) chan Point {
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var (
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x1 = p1.X
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y1 = p1.Y
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x2 = p2.X
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y2 = p2.Y
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)
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generator := make(chan Point)
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go func() {
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var (
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dx = float64(x2 - x1)
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dy = float64(y2 - y1)
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)
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var step float64
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if math.Abs(dx) >= math.Abs(dy) {
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step = math.Abs(dx)
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} else {
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step = math.Abs(dy)
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}
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dx = dx / step
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dy = dy / step
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x := float64(x1)
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y := float64(y1)
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for i := 0; i <= int(step); i++ {
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generator <- Point{
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X: int32(x),
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Y: int32(y),
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}
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x += dx
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y += dy
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}
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close(generator)
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}()
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return generator
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}
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// IterRect loops through all the points forming a rectangle between the
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// top-left point and the bottom-right point.
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func IterRect(p1, p2 Point) chan Point {
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generator := make(chan Point)
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go func() {
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var (
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TopLeft = p1
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BottomRight = p2
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TopRight = Point{
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X: BottomRight.X,
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Y: TopLeft.Y,
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}
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BottomLeft = Point{
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X: TopLeft.X,
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Y: BottomRight.Y,
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}
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dedupe = map[Point]interface{}{}
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)
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// Trace all four edges and yield it.
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var edges = []struct {
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A Point
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B Point
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}{
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{TopLeft, TopRight},
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{TopLeft, BottomLeft},
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{BottomLeft, BottomRight},
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{TopRight, BottomRight},
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}
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for _, edge := range edges {
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for pt := range IterLine(edge.A, edge.B) {
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if _, ok := dedupe[pt]; !ok {
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generator <- pt
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dedupe[pt] = nil
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}
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}
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}
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close(generator)
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}()
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return generator
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}
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// IterEllipse is a generator that draws out the pixels of an ellipse.
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func IterEllipse(rx, ry, xc, yc float32) chan Point {
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generator := make(chan Point)
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mkPoint := func(x, y float32) Point {
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return NewPoint(int32(x), int32(y))
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}
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go func() {
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var (
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dx float32
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dy float32
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d1 float32
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d2 float32
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x float32
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y = ry
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)
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d1 = (ry * ry) - (rx * rx * ry) + (0.25 * rx * rx)
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dx = 2 * ry * ry * x
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dy = 2 * rx * rx * y
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// For region 1
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for dx < dy {
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// Yields points based on 4-way symmetry.
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for _, point := range []Point{
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mkPoint(x+xc, y+yc),
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mkPoint(-x+xc, y+yc),
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mkPoint(x+xc, -y+yc),
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mkPoint(-x+xc, -y+yc),
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} {
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generator <- point
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}
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if d1 < 0 {
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x++
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dx = dx + (2 * ry * ry)
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d1 = d1 + dx + (ry * ry)
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} else {
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x++
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y--
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dx = dx + (2 * ry * ry)
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dy = dy - (2 * rx * rx)
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d1 = d1 + dx - dy + (ry * ry)
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}
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}
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d2 = ((ry * ry) + ((x + 0.5) * (x + 0.5))) +
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((rx * rx) * ((y - 1) * (y - 1))) -
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(rx * rx * ry * ry)
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// Region 2
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for y >= 0 {
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// Yields points based on 4-way symmetry.
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for _, point := range []Point{
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mkPoint(x+xc, y+yc),
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mkPoint(-x+xc, y+yc),
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mkPoint(x+xc, -y+yc),
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mkPoint(-x+xc, -y+yc),
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} {
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generator <- point
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}
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if d2 > 0 {
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y--
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dy = dy - (2 * rx * rx)
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d2 = d2 + (rx * rx) - dy
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} else {
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y--
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x++
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dx = dx + (2 * ry * ry)
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dy = dy - (2 * rx * rx)
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d2 = d2 + dx - dy + (rx * rx)
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}
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}
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close(generator)
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}()
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return generator
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}
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// IterEllipse2 iterates an Ellipse using two Points as the top-left and
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// bottom-right corners of a rectangle that encompasses the ellipse.
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func IterEllipse2(A, B Point) chan Point {
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var (
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// xc = float32(A.X+B.X) / 2
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// yc = float32(A.Y+B.Y) / 2
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xc = float32(B.X)
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yc = float32(B.Y)
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rx = float32(B.X - A.X)
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ry = float32(B.Y - A.Y)
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)
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if rx < 0 {
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rx = -rx
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}
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if ry < 0 {
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ry = -ry
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}
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log.Info("Ellipse btwn=%s-%s radius=%f,%f at center %f,%f", A, B, rx, ry, xc, yc)
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return IterEllipse(rx, ry, xc, yc)
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}
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