Package draw

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 ¶ 1.2

Drawer contains the Draw method.

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)
}

FloydSteinberg is a Drawer that is the Src Op with Floyd-Steinberg error diffusion.

var FloydSteinberg Drawer = floydSteinberg{}

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")
		}
}

type Image ¶

Image is an image.Image with a Set method to change a single pixel.

type Image interface {
		image.Image
		Set(x, y int, c color.Color)
}

type Op ¶

Op is a Porter-Duff compositing operator.

type Op int

const (
		// Over specifies ``(src in mask) over dst''.
		Over Op = iota
		// Src specifies ``src in mask''.
		Src
)

func (Op) Draw ¶ 1.2

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 ¶ 1.2

Quantizer produces a palette for an image.

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
}

type RGBA64Image ¶ 1.17

RGBA64Image extends both the Image and image.RGBA64Image interfaces with a SetRGBA64 method to change a single pixel. SetRGBA64 is equivalent to calling Set, but it can avoid allocations from converting concrete color types to the color.Color interface type.

type RGBA64Image interface {
		image.RGBA64Image
		Set(x, y int, c color.Color)
		SetRGBA64(x, y int, c color.RGBA64)
}