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Convenience package for dealing with graphics in my pixel drawing experiments.
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examples
.travis.yml
LICENSE
Makefile
README.md
animation.go
animation_test.go
base64.go
batch.go
batch_test.go
block.go
blocks.go
box.go
box_test.go
bresenham.go
bresenham_test.go
cie_lab.go
cie_lab_test.go
circle.go
cmplx.go
cmplx_test.go
colors.go
colors_test.go
doc.go
draw.go
draw_target.go
draw_test.go
drawer.go
errors.go
errors_test.go
file.go
geo.go
hsl.go
hsv.go
http.go
http_test.go
hunter_lab.go
image.go
image_test.go
imdraw.go
imdraw_test.go
int.go
int_test.go
interfaces.go
js.go
layer.go
layer_test.go
linear_scaler.go
linear_scaler_test.go
log.go
log_test.go
math.go
math_test.go
matrix.go
matrix_test.go
palette.go
palette_test.go
paletted_image.go
paletted_image_test.go
palettes.go
palettes_test.go
polygon.go
polyline.go
rand.go
rect.go
rect_test.go
resize.go
resize_test.go
signed_distance.go
simplex.go
simplex_test.go
sort.go
tiles.go
tiles_test.go
triangle.go
triangle_test.go
triangles_data.go
turtle.go
turtle_test.go
vec2.go
vec2_test.go
vec3.go
vec3_test.go
vertex.go
vertex_test.go
xyz.go

README.md

gfx

Build Status Go Report Card GoDoc License MIT

Convenience package for dealing with graphics in my pixel drawing experiments.

⚠️ NO STABILITY GUARANTEES ⚠️

Triangles

Triangles can be drawn to an image using a *gfx.DrawTarget.

gfx-triangles

package main

import "github.com/peterhellberg/gfx"

var p = gfx.PaletteFamicube

func main() {
	n := 50
	m := gfx.NewPaletted(900, 270, p, p.Color(n+7))
	t := gfx.NewDrawTarget(m)

	t.MakeTriangles(&gfx.TrianglesData{
		vx(114, 16, n+1), vx(56, 142, n+2), vx(352, 142, n+3),
		vx(350, 142, n+4), vx(500, 50, n+5), vx(640, 236, n+6),
		vx(640, 70, n+8), vx(820, 160, n+9), vx(670, 236, n+10),
	}).Draw()

	gfx.SavePNG("gfx-example-triangles.png", m)
}

func vx(x, y float64, n int) gfx.Vertex {
	return gfx.Vertex{Position: gfx.V(x, y), Color: p.Color(n)}
}

Polygons

A gfx.Polygon is represented by a list of vectors. There is also gfx.Polyline which is a slice of polygons forming a line.

gfx-example-polygon

package main

import "github.com/peterhellberg/gfx"

var edg32 = gfx.PaletteEDG32

func main() {
	m := gfx.NewNRGBA(gfx.IR(0, 0, 1024, 256))
	p := gfx.Polygon{
		{80, 40},
		{440, 60},
		{700, 200},
		{250, 230},
		{310, 140},
	}

	p.EachPixel(m, func(x, y int) {
		pv := gfx.IV(x, y)
		l := pv.To(p.Rect().Center()).Len()

		gfx.Mix(m, x, y, edg32.Color(int(l/18)%32))
	})

	for n, v := range p {
		c := edg32.Color(n * 4)

		gfx.DrawCircle(m, v, 15, 8, gfx.ColorWithAlpha(c, 96))
		gfx.DrawCircle(m, v, 16, 1, c)
	}

	gfx.SavePNG("gfx-example-polygon.png", m)
}

Blocks

You can draw (isometric) blocks using the gfx.Blocks and gfx.Block types.

gfx-example-blocks

package main

import "github.com/peterhellberg/gfx"

func main() {
	var (
		dst    = gfx.NewPaletted(898, 330, gfx.PaletteGo, gfx.PaletteGo[14])
		rect   = gfx.BoundsToRect(dst.Bounds())
		origin = rect.Center().ScaledXY(gfx.V(1.5, -2.5)).Vec3(0.55)
		blocks gfx.Blocks
	)

	for i, bc := range gfx.BlockColorsGo {
		var (
			f    = float64(i) + 0.5
			v    = f * 11
			pos  = gfx.V3(290+(v*3), 8.5*v, 9*(f+2))
			size = gfx.V3(90, 90, 90)
		)

		blocks.AddNewBlock(pos, size, bc)
	}

	blocks.Draw(dst, origin)

	gfx.SavePNG("gfx-example-blocks.png", dst)
}

Signed Distance Functions

The gfx.SignedDistance type allows you to use basic signed distance functions (and operations) to produce some interesting graphics.

gfx-example-sdf

package main

import "github.com/peterhellberg/gfx"

func main() {
	c := gfx.PaletteEDG36.Color
	m := gfx.NewImage(1024, 256, c(5))

	gfx.EachPixel(m.Bounds(), func(x, y int) {
		sd := gfx.SignedDistance{gfx.IV(x, y)}

		if d := sd.OpRepeat(gfx.V(128, 128), func(sd gfx.SignedDistance) float64 {
			return sd.OpSubtraction(sd.Circle(50), sd.Line(gfx.V(0, 0), gfx.V(64, 64)))
		}); d < 40 {
			m.Set(x, y, c(int(gfx.MathAbs(d/5))))
		}
	})

	gfx.SavePNG("gfx-example-sdf.png", m)
}

Domain Coloring

You can use the CmplxPhaseAt method on a gfx.Palette to do domain coloring.

gfx-example-domain-coloring

package main

import "github.com/peterhellberg/gfx"

const (
	w, h        = 1800, 540
	fovY        = 1.9
	aspectRatio = float64(w) / float64(h)
	centerReal  = 0
	centerImag  = 0
	ahc         = aspectRatio*fovY/2.0 + centerReal
	hfc         = fovY/2.0 + centerImag
)

func pixelCoordinates(px, py int) gfx.Vec {
	return gfx.V(
		((float64(px)/(w-1))*2-1)*ahc,
		((float64(h-py-1)/(h-1))*2-1)*hfc,
	)
}

func main() {
	var (
		p  = gfx.PaletteEN4
		p0 = pixelCoordinates(0, 0)
		p1 = pixelCoordinates(w-1, h-1)
		y  = p0.Y
		d  = gfx.V((p1.X-p0.X)/(w-1), (p1.Y-p0.Y)/(h-1))
		m  = gfx.NewImage(w, h)
	)

	for py := 0; py < h; py++ {
		x := p0.X

		for px := 0; px < w; px++ {
			cc := p.CmplxPhaseAt(gfx.CmplxCos(gfx.CmplxSin(0.42 / complex(y*x, x*x))))

			m.Set(px, py, cc)

			x += d.X
		}

		y += d.Y
	}

	gfx.SavePNG("gfx-example-domain-coloring.png", m)
}

Animation

There is rudimentary support for making animations using gfx.Animation, the animations can then be encoded into GIF.

gfx-example-animation

package main

import "github.com/peterhellberg/gfx"

func main() {
	a := &gfx.Animation{}
	p := gfx.PaletteEDG36

	var fireflower = []uint8{
		0, 1, 1, 1, 1, 1, 1, 0,
		1, 1, 2, 2, 2, 2, 1, 1,
		1, 2, 3, 3, 3, 3, 2, 1,
		1, 1, 2, 2, 2, 2, 1, 1,
		0, 1, 1, 1, 1, 1, 1, 0,
		0, 0, 0, 4, 4, 0, 0, 0,
		0, 0, 0, 4, 4, 0, 0, 0,
		4, 4, 0, 4, 4, 0, 4, 4,
		0, 4, 0, 4, 4, 0, 4, 0,
		0, 4, 4, 4, 4, 4, 4, 0,
		0, 0, 4, 4, 4, 4, 0, 0,
	}

	for i := 0; i < len(p)-4; i++ {
		t := gfx.NewTile(p[i:i+4], 8, fireflower)

		a.AddPalettedImage(gfx.NewScaledPalettedImage(t, 20))
	}

	a.SaveGIF("gfx-example-animation.gif")
}

🐢 drawing

gfx.Turtle is a small Turtle inspired drawing type. (Resize, Turn, Move, Forward, Draw)

https://www.cse.wustl.edu/~taoju/research/TurtlesforCADRevised.pdf

gfx-example-turtle

package main

import "github.com/peterhellberg/gfx"

func main() {
	m := gfx.NewImage(1024, 256)
	x := 74
	n := 21

	for j := 0; j < 4; j++ {
		gfx.NewTurtle(gfx.IV(x, 225), func(t *gfx.Turtle) {
			for i := 0; i < n; i++ {
				t.Forward(196 - float64(i))
				t.Turn(122)
			}
		}).Draw(m)

		x += 250
		n = n * 2
	}

	gfx.SavePNG("gfx-example-turtle.png", m)
}

Line drawing algorithms

Bresenham's line algorithm

gfx.DrawLineBresenham draws a line using Bresenham's line algorithm.

gfx-example-bresenham-line

package main

import "github.com/peterhellberg/gfx"

var (
	red   = gfx.BlockColorRed.Medium
	green = gfx.BlockColorGreen.Medium
	blue  = gfx.BlockColorBlue.Medium
)

func main() {
	m := gfx.NewImage(32, 16, gfx.ColorTransparent)

	gfx.DrawLineBresenham(m, gfx.V(2, 2), gfx.V(2, 14), red)
	gfx.DrawLineBresenham(m, gfx.V(6, 2), gfx.V(32, 2), green)
	gfx.DrawLineBresenham(m, gfx.V(6, 6), gfx.V(30, 14), blue)

	s := gfx.NewScaledImage(m, 16)

	gfx.SavePNG("gfx-example-bresenham-line.png", s)
}

Geometry and Transformation

The (2D) geometry and transformation types are based on those found in https://github.com/faiface/pixel (but indended for use without Pixel)

2D types

Vec

gfx.Vec is a 2D vector type with X and Y components.

Rect

gfx.Rect is a 2D rectangle aligned with the axes of the coordinate system. It is defined by two gfx.Vec, Min and Max.

Matrix

gfx.Matrix is a 2x3 affine matrix that can be used for all kinds of spatial transforms, such as movement, scaling and rotations.

gfx-readme-examples-matrix

package main

import "github.com/peterhellberg/gfx"

var en4 = gfx.PaletteEN4

func main() {
	a := &gfx.Animation{Delay: 10}

	c := gfx.V(128, 128)

	p := gfx.Polygon{
		{50, 50},
		{50, 206},
		{128, 96},
		{206, 206},
		{206, 50},
	}

	for d := 0.0; d < 360; d += 2 {
		m := gfx.NewPaletted(256, 256, en4, en4.Color(3))

		matrix := gfx.IM.RotatedDegrees(c, d)

		gfx.DrawPolygon(m, p.Project(matrix), 0, en4.Color(2))
		gfx.DrawPolygon(m, p.Project(matrix.Scaled(c, 0.5)), 0, en4.Color(1))

		gfx.DrawCircleFilled(m, c, 5, en4.Color(0))

		a.AddPalettedImage(m)
	}

	a.SaveGIF("/tmp/gfx-readme-examples-matrix.gif")
}

3D types

Vec3

gfx.Vec3 is a 3D vector type with X, Y and Z components.

Box

gfx.Box is a 3D box. It is defined by two gfx.Vec3, Min and Max

Errors

The gfx.Error type is a string that implements the error interface.

If you are using Ebiten then you can return the provided gfx.ErrDone error to exit its run loop.

HTTP

You can use gfx.GetPNG to download and decode a PNG given an URL.

Log

I find that it is fairly common for me to do some logging driven development when experimenting with graphical effects, so I've included gfx.Log, gfx.Dump, gfx.Printf and gfx.Sprintf in this package.

Math

I have included a few functions that call functions in the math package.

There is also gfx.Sign, gfx.Clamp and gfx.Lerp functions for float64.

Cmplx

I have included a few functions that call functions in the cmplx package.

Reading files

It is fairly common to read files in my experiments, so I've included gfx.ReadFile and gfx.ReadJSON in this package.

Resizing images

You can use gfx.ResizeImage to resize an image. (nearest neighbor, mainly useful for pixelated graphics)

Noise

Different types of noise is often used in procedural generation.

SimplexNoise

SimplexNoise is a speed-improved simplex noise algorithm for 2D, 3D and 4D.

gfx-example-simplex

package main

import "github.com/peterhellberg/gfx"

func main() {
	sn := gfx.NewSimplexNoise(17)

	dst := gfx.NewImage(1024, 256)

	gfx.EachImageVec(dst, gfx.ZV, func(u gfx.Vec) {
		n := sn.Noise2D(u.X/900, u.Y/900)
		c := gfx.PaletteSplendor128.At(n / 2)

		gfx.SetVec(dst, u, c)
	})

	gfx.SavePNG("gfx-example-simplex.png", dst)
}

Colors

You can construct new colors using gfx.ColorRGBA, gfx.ColorNRGBA, gfx.ColorGray, gfx.ColorGray16 and gfx.ColorWithAlpha.

There is also a gfx.LerpColors function that performs linear interpolation between two colors.

Default colors

There are a few default colors in this package, convenient when you just want to experiment, for more ambitious projects I suggest creating a gfx.Palette (or even use one of the included palettes).

Variable Color
gfx.ColorBlack gfx.ColorBlack
gfx.ColorWhite gfx.ColorWhite
gfx.ColorTransparent gfx.ColorTransparent
gfx.ColorOpaque gfx.ColorOpaque
gfx.ColorRed gfx.ColorRed
gfx.ColorGreen gfx.ColorGreen
gfx.ColorBlue gfx.ColorBlue
gfx.ColorCyan gfx.ColorCyan
gfx.ColorMagenta gfx.ColorMagenta
gfx.ColorYellow gfx.ColorYellow

Block colors

Each gfx.BlockColor consists of a Dark, Medium and Light shade of the same color.

Variable Block Color
gfx.BlockColorYellow gfx.BlockColorYellow
gfx.BlockColorOrange gfx.BlockColorOrange
gfx.BlockColorBrown gfx.BlockColorBrown
gfx.BlockColorGreen gfx.BlockColorGreen
gfx.BlockColorBlue gfx.BlockColorBlue
gfx.BlockColorPurple gfx.BlockColorPurple
gfx.BlockColorRed gfx.BlockColorRed
gfx.BlockColorWhite gfx.BlockColorWhite
gfx.BlockColorBlack gfx.BlockColorBlack
gfx.BlockColorGoGopherBlue gfx.BlockColorGoGopherBlue
gfx.BlockColorGoLightBlue gfx.BlockColorGoLightBlue
gfx.BlockColorGoAqua gfx.BlockColorGoAqua
gfx.BlockColorGoFuchsia gfx.BlockColorGoFuchsia
gfx.BlockColorGoBlack gfx.BlockColorGoBlack
gfx.BlockColorGoYellow gfx.BlockColorGoYellow

Palettes

There are a number of palettes in the gfx package, most of them are found in the Lospec Palette List.

Variable Colors Lospec Palette
gfx.Palette1Bit 2 Palette1Bit
gfx.Palette2BitGrayScale 4 Palette2BitGrayScale
gfx.PaletteEN4 4 PaletteEN4
gfx.PaletteARQ4 4 PaletteARQ4
gfx.PaletteInk 5 PaletteInk
gfx.Palette3Bit 8 Palette3Bit
gfx.PaletteEDG8 8 PaletteEDG8
gfx.PaletteAmmo8 8 PaletteAmmo8
gfx.PaletteNYX8 8 PaletteNYX8
gfx.Palette15PDX 15 Palette15PDX
gfx.PaletteCGA 16 PaletteCGA
gfx.PalettePICO8 16 PalettePICO8
gfx.PaletteNight16 16 PaletteNight16
gfx.PaletteAAP16 16 PaletteAAP16
gfx.PaletteArne16 16 PaletteArne16
gfx.PaletteEDG16 16 PaletteEDG16
gfx.Palette20PDX 20 Palette20PDX
gfx.PaletteTango 27 PaletteTango
gfx.PaletteEDG32 32 PaletteEDG32
gfx.PaletteEDG36 36 PaletteEDG36
gfx.PaletteEDG64 64 PaletteEDG64
gfx.PaletteAAP64 64 PaletteAAP64
gfx.PaletteFamicube 64 PaletteFamicube
gfx.PaletteSplendor128 128 PaletteSplendor128

The palette images were generated like this:

package main

import "github.com/peterhellberg/gfx"

func main() {
	for size, paletteLookup := range gfx.PalettesByNumberOfColors {
		for name, palette := range paletteLookup {
			dst := gfx.NewImage(size, 1)

			for x, c := range palette {
				dst.Set(x, 0, c)
			}

			filename := gfx.Sprintf("gfx-Palette%s.png", name)

			gfx.SavePNG(filename, gfx.NewResizedImage(dst, 1120, 96))
		}
	}
}

License (MIT)

Copyright (c) 2019 Peter Hellberg

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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