golang 实现clock

 1 package main
 2 
 3 import (
 4 "bufio"
 5 "image"
 6 "image/color"
 7 "image/png"
 8 "math"
 9 "os"
10 "time"
11 )
12 
13 const clock_size = 200 
14 const radius = clock_size / 3 
15 
16 var colour color.RGBA
17 
18 func circle(clock *image.RGBA) {
19 for angle := float64(0); angle < 360; angle++ {
20 radian_angle := math.Pi * 2 * angle / 360 
21 x := radius*math.Sin(radian_angle) + clock_size/2
22 y := radius*math.Cos(radian_angle) + clock_size/2
23 clock.Set(int(x), int(y), colour)
24  } 
25 }
26 func hand(clock *image.RGBA, angle float64, length float64) {
27 radian_angle := math.Pi * 2 * angle
28 x_inc := math.Sin(radian_angle)
29 y_inc := -math.Cos(radian_angle)
30 for i := float64(0); i < length; i++ {
31 x := i*x_inc + clock_size/2
32 y := i*y_inc + clock_size/2
33 clock.Set(int(x), int(y), colour)
34  } 
35 }
36 func main() {
37 clock := image.NewRGBA(image.Rect(0,0,clock_size, clock_size))
38 colour.A = 255 
39  circle(clock)
40 colour.R, colour.G, colour.B = 255,0,0
41 time := time.Now()
42 hand(clock, (float64(time.Hour())+float64(time.Minute())/60)/12, radius*0.5) // hour hand
43 colour.R, colour.G, colour.B = 0,255,0
44 hand(clock, (float64(time.Minute())+float64(time.Second())/60)/60, radius*0.6) // minute hand
45 colour.R, colour.G, colour.B = 0,0,255
46 hand(clock, float64(time.Second())/60, radius*0.8) // Second hand
47 out := bufio.NewWriter(os.Stdout)
48 defer out.Flush()
49 png.Encode(out, clock)
50 }

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