236 lines
5.8 KiB
Go
236 lines
5.8 KiB
Go
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package main
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import (
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"math"
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)
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// Draw a line using dumb
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func LineDumb(fb *Framebuffer, color uint, x0 uint, y0 uint, x1 uint, y1 uint) {
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var t float32
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for t = 0; t < 1; t += 0.01 {
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// Very simple interpolation between x and y
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x := x0 + uint(float32(x1-x0)*t)
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y := y0 + uint(float32(y1-y0)*t)
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fb.Set(x, y, color)
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}
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}
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func LineDumb2(fb *Framebuffer, color uint, x0 uint, y0 uint, x1 uint, y1 uint) {
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for x := x0; x < x1; x++ {
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// For each pixel across, compute how far across we are and interpolate y
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t := float32(x-x0) / float32(x1-x0)
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y := uint(float32(y0)*(1-t) + float32(y1)*t)
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fb.Set(x, y, color)
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}
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}
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func LineDumb3(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
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steep := false
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// This one makes sure that going pixel by pixel will not make holes in the
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// other direction by always moving in the less steep direction.
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if math.Abs(float64(x0-x1)) < math.Abs(float64(y0-y1)) {
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x0, y0 = y0, x0
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x1, y1 = y1, x1
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steep = true
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}
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// Don't let lines be invisible, always go left to right
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if x0 > x1 { // need to be left to right
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x0, x1 = x1, x0
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y0, y1 = y1, y0 // Why are we swapping these? I guess because we're swapping the points...
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}
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// Same as dumb2, going across pixel by pixel. But "x" here might actually be y
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// because of the inverted direction
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for x := x0; x <= x1; x++ {
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t := float32(x-x0) / float32(x1-x0)
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y := uint(float32(y0)*(1-t) + float32(y1)*t)
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if steep {
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fb.Set(y, uint(x), color)
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} else {
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fb.Set(uint(x), y, color)
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}
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}
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}
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func LineDumb4(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
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steep := false
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// This one makes sure that going pixel by pixel will not make holes in the
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// other direction by always moving in the less steep direction.
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if math.Abs(float64(x1-x0)) < math.Abs(float64(y1-y0)) {
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x0, y0 = y0, x0
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x1, y1 = y1, x1
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steep = true
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}
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// Don't let lines be invisible, always go left to right
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if x0 > x1 { // need to be left to right
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x0, x1 = x1, x0
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y0, y1 = y1, y0 // Why are we swapping these? I guess because we're swapping the points...
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}
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dx := x1 - x0 // These MUST be POST calcs
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dy := y1 - y0
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// Delta error or something? Basically, as we move in one direction, we get farther
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// and farther off course if we never move in the OTHER direction. This is the amount
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// of that per x direction.
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derror := math.Abs(float64(dy) / float64(dx))
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y := uint(y0)
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var err float64
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// Same as dumb2, going across pixel by pixel. But "x" here might actually be y
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// because of the inverted direction
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for x := x0; x <= x1; x++ {
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if steep {
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fb.Set(y, uint(x), color)
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} else {
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fb.Set(uint(x), y, color)
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}
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err += derror
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if err > 0.5 {
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if y1 > y0 {
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y += 1
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} else {
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y = y - 1
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}
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err -= 1
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}
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}
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}
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// For not-steep lines
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func BresenhamLow(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
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dx := x1 - x0
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dy := y1 - y0
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yi := 1 // This is the increment
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if dy < 0 { // Line moves in opposite vertical direction
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yi = -1
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dy = -dy
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}
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d := 2*dy - dx
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// Why minus dx? if slope is 0 then d is -dx. If slope is 1 then d = dy.
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// I don't know...
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y := y0
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x1u := uint(x1)
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for x := uint(x0); x <= x1u; x++ {
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fb.Set(x, uint(y), color)
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if d > 0 {
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y = y + yi
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d = d + 2*(dy-dx)
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} else {
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d = d + 2*dy
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}
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}
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}
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// For steep lines
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func BresenhamHigh(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
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dx := x1 - x0
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dy := y1 - y0
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xi := 1 // This is the increment
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if dx < 0 { // Line moves in opposite vertical direction
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xi = -1
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dx = -dx
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}
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d := 2*dx - dy
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// Why minus dx? if slope is 0 then d is -dx. If slope is 1 then d = dy.
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// I don't know...
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x := x0
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y1u := uint(y1)
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for y := uint(y0); y <= y1u; y++ {
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fb.Set(uint(x), y, color)
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if d > 0 {
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x = x + xi
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d = d + 2*(dx-dy)
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} else {
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d = d + 2*dx
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}
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}
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}
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func Bresenham(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
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if math.Abs(float64(y1-y0)) < math.Abs(float64(x1-x0)) { // This is a flatter line
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if x0 > x1 { // This line is backwards
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BresenhamLow(fb, color, x1, y1, x0, y0)
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} else {
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BresenhamLow(fb, color, x0, y0, x1, y1)
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}
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} else { // This is a steep line
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if y0 > y1 { // This line is backwards
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BresenhamHigh(fb, color, x1, y1, x0, y0)
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} else {
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BresenhamHigh(fb, color, x0, y0, x1, y1)
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}
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}
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}
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func Bresenham2(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
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dx := int(math.Abs(float64(x1 - x0)))
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sx := -1
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if x0 < x1 {
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sx = 1
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}
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dy := -int(math.Abs(float64(y1 - y0)))
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sy := -1
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if y0 < y1 {
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sy = 1
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}
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err := dx + dy
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for {
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fb.SetSafe(uint(x0), uint(y0), color)
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if x0 == x1 && y0 == y1 {
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break
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}
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e2 := 2 * err
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if e2 >= dy {
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if x0 == x1 {
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break
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}
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err += dy
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x0 += sx
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}
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if e2 <= dx {
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if y0 == y1 {
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break
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}
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err += dx
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y0 += sy
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}
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}
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}
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func LineDumb5(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
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steep := false
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// This one makes sure that going pixel by pixel will not make holes in the
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// other direction by always moving in the less steep direction.
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if math.Abs(float64(x1-x0)) < math.Abs(float64(y1-y0)) {
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x0, y0 = y0, x0
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x1, y1 = y1, x1
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steep = true
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}
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// Don't let lines be invisible, always go left to right
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if x0 > x1 { // need to be left to right
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x0, x1 = x1, x0
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y0, y1 = y1, y0 // Why are we swapping these? I guess because we're swapping the points...
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}
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dx := x1 - x0 // These MUST be POST calcs
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dy := y1 - y0
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derror2 := int(math.Abs(float64(dy))) * 2
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error2 := 0
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y := y0
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sy := 1
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if y1 <= y0 {
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sy = -1
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}
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// Same as dumb2, going across pixel by pixel. But "x" here might actually be y
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// because of the inverted direction
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for x := x0; x <= x1; x++ {
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if steep {
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fb.Set(uint(y), uint(x), color)
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} else {
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fb.Set(uint(x), uint(y), color)
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}
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error2 += derror2
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if error2 > dx {
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y = y + sy
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error2 -= dx * 2
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}
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}
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}
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