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image / draw

Package draw

go1.15
Latest Go to latest
Published: today | License: BSD-3-Clause | Standard library

Overview

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

Index

Examples

Package Files

func Draw

func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op)

Draw calls DrawMask with a nil mask.

func DrawMask

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

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.

Example (FloydSteinberg)

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

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

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) Draw

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

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.

Documentation was rendered with GOOS=linux and GOARCH=amd64.

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