justcaptcha/internal/captcha/dwelling_captcha.go

package captcha

import (
	"image"
	"justcaptcha/pkg/captcha"
	"math/rand"
	"time"

	"github.com/fogleman/gg"
)

const (
	dwImageWidth  = 160
	dwImageHeight = 40
)

type DwellingCaptcha struct {
	captcha.BaseCaptcha
}

func NewDwellingCaptcha(expiry time.Duration) *DwellingCaptcha {
	return &DwellingCaptcha{
		BaseCaptcha: captcha.BaseCaptcha{
			ExpireIn: captcha.ExpiryDate(expiry)}}
}

func (c *DwellingCaptcha) Image(style string) *image.Image {
	isDark := style == "dark"
	ctx := gg.NewContext(dwImageWidth, dwImageHeight)

	// fill background
	if isDark {
		ctx.SetRGB255(0x0a, 0x0a, 0x0a)
	} else {
		ctx.SetRGB255(0xf5, 0xf5, 0xf5)
	}
	ctx.Clear()

	// draw text
	if isDark {
		ctx.SetRGB255(0xf5, 0xf5, 0xf5)
	} else {
		ctx.SetRGB255(0x0a, 0x0a, 0x0a)
	}
	ctx.Scale(4.0, 2.7)
	ctx.DrawStringAnchored(string(c.GetAnswer()), 20, 5, .5, .5)

	// draw lines and points
	h := float64(ctx.Height())

	for i := 0; i < 24; i++ {
		x0 := rand.Float64() * h
		x1 := rand.Float64() * h
		x2 := rand.Float64() * h
		x3 := rand.Float64() * h
		ctx.DrawLine(x0, 0, h, x1)
		ctx.DrawLine(0, x2, x3, h)
		r := rand.Intn(256)
		g := rand.Intn(256)
		b := rand.Intn(256)
		ctx.SetRGB255(r, g, b)
		lw := float64(rand.Float32() * 4.0)
		if lw == 0 {
			lw = 0.1
		}
		ctx.SetLineWidth(lw)
		ctx.Stroke()
	}

	i := ctx.Image()
	return &i
}