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tomo-old/artist/shapes/line.go

113 lines
2.1 KiB
Go

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