111 lines
2.0 KiB
Go
111 lines
2.0 KiB
Go
package shapes
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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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// ColorLine draws a line from one point to another with the specified weight
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// and color.
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func ColorLine (
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destination canvas.Canvas,
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color color.RGBA,
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weight int,
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min image.Point,
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max image.Point,
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) (
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updatedRegion image.Rectangle,
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) {
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updatedRegion = image.Rectangle { Min: min, Max: max }.Canon()
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updatedRegion.Max.X ++
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updatedRegion.Max.Y ++
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data, stride := destination.Buffer()
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bounds := destination.Bounds()
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context := linePlottingContext {
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plottingContext: plottingContext {
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dstData: data,
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dstStride: stride,
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color: color,
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weight: weight,
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bounds: bounds,
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},
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min: min,
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max: max,
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}
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if abs(max.Y - min.Y) < abs(max.X - min.X) {
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if max.X < min.X { context.swap() }
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context.lineLow()
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} else {
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if max.Y < min.Y { context.swap() }
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context.lineHigh()
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}
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return
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}
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type linePlottingContext struct {
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plottingContext
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min image.Point
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max image.Point
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}
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func (context *linePlottingContext) swap () {
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temp := context.max
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context.max = context.min
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context.min = temp
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}
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func (context linePlottingContext) lineLow () {
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deltaX := context.max.X - context.min.X
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deltaY := context.max.Y - context.min.Y
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yi := 1
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if deltaY < 0 {
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yi = -1
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deltaY *= -1
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}
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D := (2 * deltaY) - deltaX
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point := context.min
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for ; point.X < context.max.X; point.X ++ {
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context.plotColor(point)
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if D > 0 {
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D += 2 * (deltaY - deltaX)
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point.Y += yi
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} else {
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D += 2 * deltaY
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}
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}
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}
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func (context linePlottingContext) lineHigh () {
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deltaX := context.max.X - context.min.X
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deltaY := context.max.Y - context.min.Y
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xi := 1
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if deltaX < 0 {
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xi = -1
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deltaX *= -1
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}
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D := (2 * deltaX) - deltaY
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point := context.min
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for ; point.Y < context.max.Y; point.Y ++ {
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context.plotColor(point)
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if D > 0 {
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point.X += xi
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D += 2 * (deltaX - deltaY)
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} else {
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D += 2 * deltaX
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}
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}
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}
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func abs (n int) int {
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if n < 0 { n *= -1}
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return n
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}
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