raster

README

raster - a convenience package to render vector graphics as images

Overview

The raster package helps visualize vector graphics in the form of a PNG image. It can be used with the "golang.org/x/image/vector" package. Using primatives in that package, the raster package provides support for rendering solid lines and approximate circles. It also provides a convenience function to render the vector paths to an image. Documentation for the raster package should be available on go.dev.

The package provides a simple examples/trace.go program that uses the package to render something resembling a PCB copper trace.

$ go run examples/trace.go --dest image.png

creates the following image.png file:

License info

The raster program is distributed with the same BSD 3-clause license as that used by golang itself.

Reporting bugs and feature requests

The package raster has been developed purely out of curiosity for and as part of a project to create simple PCBs using a Snapmaker 2 3D printer (with laser and CNC tool heads). If you find a bug or want to suggest a feature addition, please use the bug tracker.

Documentation

Overview

Package raster contains some convenience functions for creating "golang.org/x/image/vector" paths and rendering them into images.

Index

• func LineTo(r Scriber, capped bool, oX, oY, nX, nY, width float64)
• func PointAt(r Scriber, x, y, width float64)
• func SquareAt(r Scriber, x, y, width float64)
• type Entry
• type Operator
  • func (op Operator) String() string
• type Rasterizer
  • func NewRasterizer() *Rasterizer
  • func (r *Rasterizer) ClosePath()
  • func (r *Rasterizer) CubeTo(a, b, c, d, e, f float64)
  • func (r *Rasterizer) LineTo(x, y float64)
  • func (r *Rasterizer) MoveTo(x, y float64)
  • func (r *Rasterizer) Render(im draw.Image, x, y float64, col color.Color)
  • func (r *Rasterizer) Reset()
• type Scriber
• type Segment

Functions

func LineTo

func LineTo(r Scriber, capped bool, oX, oY, nX, nY, width float64)

LineTo renders a line segment from (oX,oY) to (nX,nY) with the specified perpendicular width. The capped value adds rounded end-caps to the line of radius half of the width (as approximated with Bezier curves).

func PointAt

func PointAt(r Scriber, x, y, width float64)

PointAt renders an approximate "circle" via 4 cubic Bezier curves describing the arc of the 4 quadrants.

func SquareAt

func SquareAt(r Scriber, x, y, width float64)

SquareAt renders a width by width square centered at (x,y).

Types

type Entry

type Entry struct {
	Closed                 bool
	Path                   []Segment
	MinX, MaxX, MinY, MaxY float64
}

Entry captures the signature of a series of segments.

type Operator

type Operator int

func (Operator) String

func (op Operator) String() string

type Rasterizer

type Rasterizer struct {
	Entries []Entry
}

Rasterizer is a wrapper for the golang.org/x/image/vector.Rasterizer type which maps float64 arguments to float32 bit calls.

func NewRasterizer

func NewRasterizer() *Rasterizer

NewRasterizer allocates a new rasterizer.

func (*Rasterizer) ClosePath

func (r *Rasterizer) ClosePath()

ClosePath forms a loop back line from the pen to the start of the path.

func (*Rasterizer) CubeTo

func (r *Rasterizer) CubeTo(a, b, c, d, e, f float64)

CubeTo constructs a cubic Bezier curve using the supplied parameters, from the pen location to point (e,f), which becomes the updated pen location.

func (*Rasterizer) LineTo

func (r *Rasterizer) LineTo(x, y float64)

LineTo constructs a straight line from the pen to the target (x,y) coordinate, and updates the pen to this location.

func (*Rasterizer) MoveTo

func (r *Rasterizer) MoveTo(x, y float64)

MoveTo sets the rasterizer pen to the coordinate (x,y).

func (*Rasterizer) Render

func (r *Rasterizer) Render(im draw.Image, x, y float64, col color.Color)

Render places the entries of r into the im at (x,y) offset.

func (*Rasterizer) Reset

func (r *Rasterizer) Reset()

Reset resets the memory of the rasterizer.

type Scriber

type Scriber interface {
	MoveTo(x, y float64)
	LineTo(x, y float64)
	CubeTo(a, b, c, d, e, f float64)
	ClosePath()
}

Scriber is the interface for drawing vector graphics.

type Segment

type Segment struct {
	Op   Operator
	Args []float64
}

Segment is a single line.