/
spin.go
112 lines (107 loc) · 2.71 KB
/
spin.go
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package paint
import (
"errors"
"image"
"image/draw"
)
// 用于翻转的常量
const (
Horizontal = 0
Vertical = 1
)
// 用于旋转的常量
const (
L0 = 0
R0 = 0
L90 = +1
R90 = -1
L180 = +2
R180 = -2
L270 = R90
R270 = L90
)
// 翻转函数，要求两个图像大小契合，act&1 == 0则左右翻转，否则垂直翻转。
func Overturn(dst draw.Image, src image.Image, act int) error {
var to func(int, int) (int, int)
sr := src.Bounds()
dr := dst.Bounds()
W := dr.Max.X - dr.Min.X
H := dr.Max.Y - dr.Min.Y
if H <= 0 || W <= 0 {
return errors.New("target image is empty or noncanonical")
}
if sr.Min.X >= sr.Max.X || sr.Min.Y >= sr.Max.Y {
return errors.New("source image is empty or noncanonical")
}
if sr.Max.X-sr.Min.X != W || sr.Max.Y-sr.Min.Y != H {
return errors.New("target and source must be same size!")
}
if act&1 == 0 {
to = func(x, y int) (int, int) {
return W - 1 - x, y
}
} else {
to = func(x, y int) (int, int) {
return x, H - 1 - y
}
}
for i := 0; i < W; i++ {
for j := 0; j < H; j++ {
x, y := to(i, j)
dst.Set(dr.Min.X+x, dr.Min.Y+y, src.At(sr.Min.X+i, sr.Min.Y+j))
}
}
return nil
}
// 旋转，每单位1代表左旋90度。注意采用的是向右向上的直角坐标系，和图像的向右向下不同。
// 本包的函数都是采用向右向上的直角坐标系。因此在图像显示上，每单位1右旋90度。
func Rotate(dst draw.Image, src image.Image, act int) error {
var to func(int, int) (int, int)
sr := src.Bounds()
dr := dst.Bounds()
W := dr.Max.X - dr.Min.X
H := dr.Max.Y - dr.Min.Y
if H <= 0 || W <= 0 {
return errors.New("target image is empty or noncanonical")
}
if sr.Min.X >= sr.Max.X || sr.Min.Y >= sr.Max.Y {
return errors.New("source image is empty or noncanonical")
}
switch act %= 4; act {
case 2, -2:
if sr.Max.X-sr.Min.X != W || sr.Max.Y-sr.Min.Y != H {
return errors.New("target and source must be same size!")
}
to = func(x, y int) (int, int) {
return W - 1 - x, H - 1 - y
}
case 1, -3:
if sr.Max.X-sr.Min.X != H || sr.Max.Y-sr.Min.Y != W {
return errors.New("target and source must be same size!")
}
to = func(x, y int) (int, int) {
return H - 1 - y, x
}
case -1, 3:
if sr.Max.X-sr.Min.X != H || sr.Max.Y-sr.Min.Y != W {
return errors.New("target and source must be same size!")
}
to = func(x, y int) (int, int) {
return y, W - 1 - x
}
case 0:
if sr.Max.X-sr.Min.X != W || sr.Max.Y-sr.Min.Y != H {
return errors.New("target and source must be same size!")
}
to = func(x, y int) (int, int) {
return x, y
}
}
for i := 0; i < W; i++ {
for j := 0; j < H; j++ {
x, y := to(i, j)
dst.Set(dr.Min.X+x, dr.Min.Y+y, src.At(sr.Min.X+i, sr.Min.Y+j))
}
}
return nil
}