captcha

README

Package captcha provides an easy to use, unopinionated API for captcha generation.

Why another captcha generator?

I want a simple and framework-independent way to generate captcha. It also should be flexible, at least allow me to pick my favorite font.

install

go get github.com/steambap/captcha

usage

func handle(w http.ResponseWriter, r *http.Request) {
	// create a captcha of 150x50px
	data, _ := captcha.New(150, 50)

	// session come from other library such as gorilla/sessions
	session.Values["captcha"] = data.Text
	session.Save(r, w)
	// send image data to client
	data.WriteImage(w)
}

documentation | example

sample image

Contributing

If your found a bug, please contribute! see contributing.md for more detail.

License

MIT

Documentation

Overview

Package captcha provides an easy to use, unopinionated API for captcha generation

Index

• func LoadFont(fontData []byte) error
• func LoadFontFromReader(reader io.Reader) error
• type Data
  • func New(width int, height int, option ...SetOption) (*Data, error)
  • func NewMathExpr(width int, height int, option ...SetOption) (*Data, error)
  • func (data *Data) WriteGIF(w io.Writer, o *gif.Options) error
  • func (data *Data) WriteImage(w io.Writer) error
  • func (data *Data) WriteJPG(w io.Writer, o *jpeg.Options) error
• type Options
• type SetOption

Functions

func LoadFont

func LoadFont(fontData []byte) error

LoadFont let you load an external font.

func LoadFontFromReader

func LoadFontFromReader(reader io.Reader) error

LoadFontFromReader load an external font from an io.Reader interface.

Types

type Data

type Data struct {
	// Text is captcha solution.
	Text string
	// contains filtered or unexported fields
}

Data is the result of captcha generation. It has a `Text` field and a private `img` field that will be used in `WriteImage` receiver.

func New

func New(width int, height int, option ...SetOption) (*Data, error)

New creates a new captcha. It returns captcha data and any freetype drawing error encountered.

func NewMathExpr

func NewMathExpr(width int, height int, option ...SetOption) (*Data, error)

NewMathExpr creates a new captcha. It will generate a image with a math expression like `1 + 2`.

func (*Data) WriteGIF

func (data *Data) WriteGIF(w io.Writer, o *gif.Options) error

WriteGIF encodes image data in GIF format and writes to an io.Writer. It returns possible error from GIF encoding.

func (*Data) WriteImage

func (data *Data) WriteImage(w io.Writer) error

WriteImage encodes image data and writes to an io.Writer. It returns possible error from PNG encoding.

func (*Data) WriteJPG

func (data *Data) WriteJPG(w io.Writer, o *jpeg.Options) error

WriteJPG encodes image data in JPEG format and writes to an io.Writer. It returns possible error from JPEG encoding.

type Options

type Options struct {
	// BackgroundColor is captcha image's background color.
	// It defaults to color.Transparent.
	BackgroundColor color.Color
	// CharPreset decides what text will be on captcha image.
	// It defaults to digit 0-9 and all English alphabet.
	// ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
	CharPreset string
	// TextLength is the length of captcha text.
	// It defaults to 4.
	TextLength int
	// CurveNumber is the number of curves to draw on captcha image.
	// It defaults to 2.
	CurveNumber int
	// FontDPI controls DPI (dots per inch) of font.
	// The default is 72.0.
	FontDPI float64
	// FontScale controls the scale of font.
	// The default is 1.0.
	FontScale float64
	// Noise controls the number of noise drawn.
	// A noise dot is drawn for every 28 pixel by default.
	// The default is 1.0.
	Noise float64
	// Palette is the set of colors to chose from
	Palette color.Palette
	// contains filtered or unexported fields
}

Options manage captcha generation details.

type SetOption

type SetOption func(*Options)

SetOption is a function that can be used to modify default options.