import "image/draw"
Package draw provides image composition functions.
See "The Go image/draw package" for an introduction to this package: https://golang.org/doc/articles/image_draw.html
func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op)
Draw calls DrawMask with a nil mask.
func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op)
DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque.
type Drawer interface {
// Draw aligns r.Min in dst with sp in src and then replaces the
// rectangle r in dst with the result of drawing src on dst.
Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point)
}
Drawer contains the Draw method.
Code:
const width = 130
const height = 50
im := image.NewGray(image.Rectangle{Max: image.Point{X: width, Y: height}})
for x := 0; x < width; x++ {
for y := 0; y < height; y++ {
dist := math.Sqrt(math.Pow(float64(x-width/2), 2)/3+math.Pow(float64(y-height/2), 2)) / (height / 1.5) * 255
var gray uint8
if dist > 255 {
gray = 255
} else {
gray = uint8(dist)
}
im.SetGray(x, y, color.Gray{Y: 255 - gray})
}
}
pi := image.NewPaletted(im.Bounds(), []color.Color{
color.Gray{Y: 255},
color.Gray{Y: 160},
color.Gray{Y: 70},
color.Gray{Y: 35},
color.Gray{Y: 0},
})
draw.FloydSteinberg.Draw(pi, im.Bounds(), im, image.ZP)
shade := []string{" ", "░", "▒", "▓", "█"}
for i, p := range pi.Pix {
fmt.Print(shade[p])
if (i+1)%width == 0 {
fmt.Print("\n")
}
}
var FloydSteinberg Drawer = floydSteinberg{}
FloydSteinberg is a Drawer that is the Src Op with Floyd-Steinberg error diffusion.
type Image interface {
image.Image
Set(x, y int, c color.Color)
}
Image is an image.Image with a Set method to change a single pixel.
type Op int
Op is a Porter-Duff compositing operator.
const (
// Over specifies ``(src in mask) over dst''.
Over Op = iota
// Src specifies ``src in mask''.
Src
)
func (op Op) Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point)
Draw implements the Drawer interface by calling the Draw function with this Op.
type Quantizer interface {
// Quantize appends up to cap(p) - len(p) colors to p and returns the
// updated palette suitable for converting m to a paletted image.
Quantize(p color.Palette, m image.Image) color.Palette
}
Quantizer produces a palette for an image.