💾 Archived View for thrig.me › blog › 2023 › 05 › 16 › circle.go captured on 2023-05-24 at 18:07:05.
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// circle - draw circle like things
package main
import (
"fmt"
"image"
"image/color"
"image/draw"
"image/gif"
"log"
"math"
"math/rand"
"os"
"time"
)
type Circle struct {
x int
y int
r int
c uint8
h1 int // derived from y, radius, to find where circle is
}
var palette = []color.Color{
color.White,
color.Black,
color.NRGBA{255, 114, 114, 255},
color.NRGBA{255, 203, 114, 255},
color.NRGBA{255, 255, 114, 255},
color.NRGBA{57, 128, 57, 255},
color.NRGBA{114, 114, 255, 255},
color.NRGBA{99, 58, 130, 255},
color.NRGBA{238, 237, 238, 255},
color.NRGBA{78, 78, 78, 255},
color.NRGBA{99, 99, 99, 255},
color.NRGBA{130, 130, 130, 255},
color.NRGBA{156, 156, 156, 255},
color.NRGBA{208, 208, 208, 255},
color.NRGBA{237, 237, 237, 255},
color.NRGBA{239, 239, 239, 255},
/*
color.NRGBA{239,239,239, 255},
color.NRGBA{237,237,237, 255},
color.NRGBA{208,208,208, 255},
color.NRGBA{156,156,156, 255},
color.NRGBA{130,130,130, 255},
color.NRGBA{99,99,99, 255},
color.NRGBA{78,78,78, 255},
*/
/*
//color.NRGBA{0, 105, 148, 255},
color.NRGBA{0x00, 0x8D, 0xC7, 255},
color.NRGBA{0x00, 0xB1, 0xFA, 255},
*/
}
const (
fg_color = 0
bg_color = 1
cidx1 = 2
cidx2 = 3
cidx3 = 4
cidx4 = 5
cidx5 = 6
cidx6 = 7
cidx7 = 8
//bg_color = 0
//fg_color = 1
//bl_color = 2
)
func cdhline(canvas *image.Paletted, c uint8, space, x1, x2, y int) {
for x := x1; x <= x2; x += space {
canvas.SetColorIndex(x, y, c)
}
}
func chline(canvas *image.Paletted, c uint8, x1, x2, y int) {
for x := x1; x <= x2; x++ {
canvas.SetColorIndex(x, y, c)
}
}
func chline2(canvas *image.Paletted, c uint8, x1, x2, y int) {
x1 = x1 + irand(13) - 1
x2 = x2 + irand(21) - 7
for x := x1; x <= x2; x += 4 {
canvas.SetColorIndex(x, y, c)
}
}
func wcdhline(canvas *image.Paletted, c uint8, space, x1, x2, y int) {
//x1 = x1 + irand(3) - 1
x2 = x2 + irand(7) - 3
for x := x1; x <= x2; x += space {
canvas.SetColorIndex(x, y, c)
canvas.SetColorIndex(x-1, y, c)
canvas.SetColorIndex(x-1, y+1, c)
canvas.SetColorIndex(x, y+1, c)
canvas.SetColorIndex(x-1, y-1, c)
canvas.SetColorIndex(x-2, y, c)
canvas.SetColorIndex(x-2, y+2, c)
canvas.SetColorIndex(x-1, y+2, c)
canvas.SetColorIndex(x-2, y-2, c)
canvas.SetColorIndex(x-4, y-1, c)
canvas.SetColorIndex(x-3, y+3, c)
canvas.SetColorIndex(x-2, y+3, c)
}
}
func circle_fill(canvas *image.Paletted, circ *Circle, c uint8) {
fmt.Fprintf(os.Stderr, "dbg y=%v r=%v %v\n", circ.y, circ.r, circ.y-circ.r)
for y := 0; y <= circ.r; y++ {
angle := math.Asin(float64(y) / float64(circ.r))
x := int(math.Cos(angle) * float64(circ.r))
start := circ.x - x
end := circ.x + x
chline(canvas, c, start, end, circ.y+y)
chline(canvas, c, start, end, circ.y-y)
}
}
func hline(canvas *image.Paletted, x1, x2, y int) {
for x := x1; x <= x2; x++ {
canvas.SetColorIndex(x, y, fg_color)
}
}
func irand(max int) int {
return int(rand.Int63n(int64(max)))
}
func main() {
rand.Seed(time.Now().UTC().UnixNano())
with_gif("out.gif")
fmt.Fprintf(os.Stderr, "ok\n") // KLUGE for "fmt" import
}
func make_circle(x, y, r int, c uint8) Circle {
circ := Circle{
x: x,
y: y,
r: r,
c: c,
}
circ.h1 = y - r
// we really only need half the circle to find it
//circ.h2 = y + r
return circ
}
func rad2deg(radians float64) float64 {
return radians * 180 / math.Pi
}
func with_gif(file string) {
out, err := os.Create(file)
if err != nil {
log.Fatal(err)
}
defer out.Close()
xsize := 320
ysize := 240
rect := image.Rect(0, 0, xsize, ysize)
canvas := image.NewPaletted(rect, palette)
draw.Draw(canvas, canvas.Bounds(), &image.Uniform{palette[bg_color]}, image.ZP, draw.Src)
var circles []Circle
circles = append(circles, make_circle(160, 120, 104, fg_color))
var cnum uint8 = cidx1
counter := -1
// with image-global horizontal lines of some spacing...
for y := 0; y < ysize; y += 9 {
for _, circ := range circles {
if y >= circ.h1 && y <= circ.y { // half-circle intersects?
opp := circ.y - y
angle := math.Asin(float64(opp) / float64(circ.r))
adj := int(math.Cos(angle) * float64(circ.r))
start := circ.x - adj
end := circ.x + adj
cdhline(canvas, cnum, 3, start, end, circ.y-opp) // top half
chline2(canvas, cnum+7, start, end, circ.y+opp + 3)
counter++
if counter&1 == 1 {
cnum++
if cnum > cidx7 {
cnum = cidx1
}
}
} else {
//cdhline(canvas, fg_color, 1, 0, xsize, y)
}
}
}
//cdhline(canvas, 4, 5, 0, xsize, 116)
//dot := make_circle(130, 70, 16)
//circle_fill(canvas, &dot, bg_color)
options := &gif.Options{
NumColors: len(palette),
}
gif.Encode(out, canvas, options)
}