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 }