GoCaptcha

Behavior Captcha Of Golang

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GoCaptcha is a powerful, modular, and highly customizable behavioral CAPTCHA library that supports multiple interactive CAPTCHA types: Click, Slide, Drag-Drop, and Rotate.

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Ecosystem

Project	Desc
document	GoCaptcha Documentation
online demo	GoCaptcha Online Demo
go-captcha-example	Golang + Web + APP Example
go-captcha-assets	Embedded Resource Assets for Golang
go-captcha	Golang CAPTCHA Library
go-captcha-jslib	JavaScript CAPTCHA Library
go-captcha-vue	Vue CAPTCHA Library
go-captcha-react	React CAPTCHA Library
go-captcha-angular	Angular CAPTCHA Library
go-captcha-svelte	Svelte CAPTCHA Library
go-captcha-solid	Solid CAPTCHA Library
go-captcha-uni	UniApp CAPTCHA, compatible with Apps, Mini-Programs, and Fast Apps
go-captcha-service	GoCaptcha Service, supports binary and Docker image deployment, provides HTTP/gRPC interfaces, supports standalone and distributed modes (service discovery, load balancing, dynamic configuration)
go-captcha-service-sdk	GoCaptcha Service SDK Toolkit, includes HTTP/gRPC request interfaces, supports static mode, service discovery, and load balancing.
...

Core Features

Diverse CAPTCHA Types: Supports Click, Slide, Rotate, and Drag behavioral CAPTCHAs, suitable for various interaction scenarios.
Highly Customizable: Flexible configuration of images, fonts, colors, angles, sizes, etc., through Options and Resources.
Advanced Image Processing: Built-in dynamic image generation and processing, supporting main images, thumbnails, puzzle pieces, and shadow effects.
Modular Architecture: Clear code structure, adhering to Go best practices, making it easy to extend and maintain.
High-Performance Design: Optimized resource management and image generation, suitable for high-concurrency scenarios.
Cross-Platform Compatibility: Generated CAPTCHA images can be seamlessly integrated into web applications, mobile apps, or other systems requiring CAPTCHAs.

CAPTCHA Types

go-captcha supports the following four CAPTCHA types, each with unique interaction methods, generation logic, and application scenarios:

Click CAPTCHA: Users click specified points or characters on the main image, supporting text and graphic modes.
Slide CAPTCHA: Users slide a puzzle piece to the correct position on the main image, supporting basic and drag-drop modes.
Drag-Drop CAPTCHA: A variant of the Slide CAPTCHA, allowing users to drag-drop a puzzle piece to a target position within a larger range.
Rotate CAPTCHA: Users rotate a thumbnail to align with the main image’s angle.

Install

$ go get -u github.com/wenlng/go-captcha/v2@latest

Import Module

package main

// Import modules on demand
import "github.com/wenlng/go-captcha/v2/${click|slide|rotate}"

func main(){
   // ...
}

🖖 Click CAPTCHA

The Click CAPTCHA requires users to click specified points or characters on the main image, ideal for quick verification scenarios. It supports two modes:

Text Mode：Displays characters (e.g., letters, numbers, or Chinese characters), and users click the corresponding characters.
Graphic Mode：Displays graphics (e.g., icons or shapes), and users click the corresponding graphics.

How It Works

Generate Main Image (masterImage): Contains randomly distributed points or characters, typically in JPEG format.
Generate Thumbnail (thumbImage): Displays the target points or characters to be clicked, typically in PNG format.
User Interaction: Users click coordinates on the main image, and the frontend captures and sends the coordinates to the backend.
Verification Logic: The backend compares the clicked coordinates with the target points (dots) to verify a match.

Code Example

package main

import (
	"encoding/json"
	"fmt"
	"image"
	"log"
	"io/ioutil"

	"github.com/golang/freetype"
	"github.com/golang/freetype/truetype"
	"github.com/wenlng/go-captcha/v2/base/option"
	"github.com/wenlng/go-captcha/v2/click"
	"github.com/wenlng/go-captcha/v2/base/codec"
)

var textCapt click.Captcha

func init() {
	builder := click.NewBuilder(
		click.WithRangeLen(option.RangeVal{Min: 4, Max: 6}),
		click.WithRangeVerifyLen(option.RangeVal{Min: 2, Max: 4}),
	)

	// You can use preset material resources：https://github.com/wenlng/go-captcha-assets
	fontN, err := loadFont("../resources/fzshengsksjw_cu.ttf")
	if err != nil {
		log.Fatalln(err)
	}

	bgImage, err := loadPng("../resources/bg.png")
	if err != nil {
		log.Fatalln(err)
	}

	builder.SetResources(
		click.WithChars([]string{
			"1A",
			"5E",
			"3d",
			"0p",
			"78",
			"DL",
			"CB",
			"9M",
			// ...
		}),
		click.WithFonts([]*truetype.Font{
			fontN,
		}),
		click.WithBackgrounds([]image.Image{
			bgImage,
		}),
	)

	textCapt= builder.Make()
}

func loadPng(p string) (image.Image, error) {
	imgBytes, err := ioutil.ReadFile(p)
	if err != nil {
		return nil, err
	}
	return codec.DecodeByteToPng(imgBytes)
}

func loadFont(p string) (*truetype.Font, error) {
	fontBytes, err := ioutil.ReadFile(p)
	if err != nil {
		panic(err)
	}
	return freetype.ParseFont(fontBytes)
}


func main() {
	captData, err := textCapt.Generate()
	if err != nil {
		log.Fatalln(err)
	}

	dotData := captData.GetData()
	if dotData == nil {
		log.Fatalln(">>>>> generate err")
	}

	dots, _ := json.Marshal(dotData)
	fmt.Println(">>>>> ", string(dots))

	var mBase64, tBase64 string
	mBase64, err = captData.GetMasterImage().ToBase64()
	if err != nil {
		fmt.Println(err)
	}
	tBase64, err = captData.GetThumbImage().ToBase64()
	if err != nil {
		fmt.Println(err)
	}
	
	fmt.Println(">>>>> ", mBase64)
	fmt.Println(">>>>> ", tBase64)
	
	//err = captData.GetMasterImage().SaveToFile("../resources/master.jpg", option.QualityNone)
	//if err != nil {
	//	fmt.Println(err)
	//}
	//err = captData.GetThumbImage().SaveToFile("../resources/thumb.png")
	//if err != nil {
	//	fmt.Println(err)
	//}
}

Make Instance

builder.Make()
builder.MakeShape()

Configuration Options

click.NewBuilder(click.WithXxx(), ...) OR builder.SetOptions(click.WithXxx(), ...)

Options	Desc
Main Image
click.WithImageSize(option.Size)	Set main image size, default 300x220
click.WithRangeLen(option.RangeVal)	Set range for random content length
click.WithRangeAnglePos([]option.RangeVal)	Set range for random angles
click.WithRangeSize(option.RangeVal)	Set range for random content size
click.WithRangeColors([]string)	Set random colors
click.WithDisplayShadow(bool)	Enable/disable shadow display
click.WithShadowColor(string)	Set shadow color
click.WithShadowPoint(option.Point)	Set shadow offset position
click.WithImageAlpha(float32)	Set main image transparency
click.WithUseShapeOriginalColor(bool)	Use original graphic color (valid for graphic mode)
Thumbnail
click.WithThumbImageSize(option.Size)	Set thumbnail size, default 150x40
click.WithRangeVerifyLen(option.RangeVal)	Set range for random verification content length
click.WithDisabledRangeVerifyLen(bool)	Disable random verification length, matches main content
click.WithRangeThumbSize(option.RangeVal)	Set range for random thumbnail content size
click.WithRangeThumbColors([]string)	Set range for random thumbnail colors
click.WithRangeThumbBgColors([]string)	Set range for random thumbnail background colors
click.WithIsThumbNonDeformAbility(bool)	Prevent thumbnail content deformation
click.WithThumbBgDistort(int)	Set thumbnail background distortion (option.DistortLevel1 to option.DistortLevel5)
click.WithThumbBgCirclesNum(int)	Set number of small circles in thumbnail background
click.WithThumbBgSlimLineNum(int)	Set number of lines in thumbnail background

Set Resources

builder.SetResources(click.WithXxx(), ...)

Options	Desc
click.WithChars([]string)	Set text seed
click.WithShapes(map[string]image.Image)	Set graphic seed
click.WithFonts([]*truetype.Font)	Set fonts
click.WithBackgrounds([]image.Image)	Set main image backgrounds
click.WithThumbBackgrounds([]image.Image)	Set thumbnail backgrounds

Captcha Data

captData, err := capt.Generate()

Method	Desc
GetData() map[int]*Dot	Get verification data
GetMasterImage() imagedata.JPEGImageData	Get main image
GetThumbImage() imagedata.PNGImageData	Get thumbnail

Validate the captcha

ok := click.Validate(srcX, srcY, X, Y, width, height, paddingValue)

Params	Desc
srcX	User X-axis
srcY	User Y-axis
X	X-axis
Y	Y-axis
width	Width
height	Height
paddingValue	Set the padding value

Notes

The character set (chars) or graphic set (shapes) must be longer than rangeLen.Max, otherwise CharRangeLenErr or ShapesRangeLenErr will be triggered.
Graphic mode requires valid image resources (shapeMaps), otherwise ShapesTypeErr will be triggered.
Background images must not be empty, otherwise EmptyBackgroundImageErr will be triggered.

🖖 Slide Or Drag-Drop CAPTCHA

The Slide CAPTCHA requires users to slide a puzzle piece to the correct position on the main image. It supports two modes:

Basic Mode: The puzzle piece slides along a fixed Y-axis, suitable for simple verification scenarios.
Drag-Drop Mode: The puzzle piece can be freely dragged within a larger range, suitable for scenarios requiring higher interaction freedom.

How It Works

Generate Main Image (masterImage): Contains the puzzle piece’s notch and shadow effects, typically in JPEG format.
Generate Tile Image (tileImage): The puzzle piece users need to slide, typically in PNG format.
User Interaction: Users slide the puzzle piece to the target position (TileX, TileY), and the frontend captures the final coordinates.
Verification Logic: The backend compares the user’s slide position with the target position to verify a match.

Code Example

package main

import (
	"encoding/json"
	"fmt"
	"image"
	"log"
	"io/ioutil"

	"github.com/wenlng/go-captcha/v2/base/option"
	"github.com/wenlng/go-captcha/v2/slide"
	"github.com/wenlng/go-captcha/v2/base/codec"
)

var slideTileCapt slide.Captcha

func init() {
	builder := slide.NewBuilder()

	// You can use preset material resources：https://github.com/wenlng/go-captcha-assets
	bgImage, err := loadPng("../resources/bg.png")
	if err != nil {
		log.Fatalln(err)
	}

	bgImage1, err := loadPng("../resources/bg1.png")
	if err != nil {
		log.Fatalln(err)
	}

	graphs := getSlideTileGraphArr()

	builder.SetResources(
		slide.WithGraphImages(graphs),
		slide.WithBackgrounds([]image.Image{
			bgImage,
			bgImage1,
		}),
	)

	slideTileCapt = builder.Make()
	
	// drag-drop mode
	//dragDropCapt = builder.MakeDragDrop()
}

func getSlideTileGraphArr() []*slide.GraphImage {
	tileImage1, err := loadPng("../resources/tile-1.png")
	if err != nil {
		log.Fatalln(err)
	}

	tileShadowImage1, err := loadPng("../resources/tile-shadow-1.png")
	if err != nil {
		log.Fatalln(err)
	}
	tileMaskImage1, err := loadPng("../resources/tile-mask-1.png")
	if err != nil {
		log.Fatalln(err)
	}

	return []*slide.GraphImage{
		{
			OverlayImage: tileImage1,
			ShadowImage:  tileShadowImage1,
			MaskImage:    tileMaskImage1,
		},
	}
}

func main() {
	captData, err := slideTileCapt.Generate()
	if err != nil {
		log.Fatalln(err)
	}

	blockData := captData.GetData()
	if blockData == nil {
		log.Fatalln(">>>>> generate err")
	}

	block, _ := json.Marshal(blockData)
	fmt.Println(">>>>>", string(block))

	var mBase64, tBase64 string
	mBase64, err = captData.GetMasterImage().ToBase64()
	if err != nil {
		fmt.Println(err)
	}
	tBase64, err = captData.GetTileImage().ToBase64()
	if err != nil {
		fmt.Println(err)
	}

	fmt.Println(">>>>> ", mBase64)
	fmt.Println(">>>>> ", tBase64)
	
	//err = captData.GetMasterImage().SaveToFile("../resources/master.jpg", option.QualityNone)
	//if err != nil {
	//	fmt.Println(err)
	//}
	//err = captData.GetTileImage().SaveToFile("../resources/thumb.png")
	//if err != nil {
	//	fmt.Println(err)
	//}
}

func loadPng(p string) (image.Image, error) {
	imgBytes, err := ioutil.ReadFile(p)
	if err != nil {
		return nil, err
	}
	return codec.DecodeByteToPng(imgBytes)
}

Make Instance

builder.Make()
builder.MakeDragDrop()

Configuration Options

slide.NewBuilder(slide.WithXxx(), ...) OR builder.SetOptions(slide.WithXxx(), ...)

Options	Desc
slide.WithImageSize(*option.Size)	Set main image size, default 300x220
slide.WithImageAlpha(float32)	Set main image transparency
slide.WithRangeGraphSize(val option.RangeVal)	Set range for random graphic size
slide.WithRangeGraphAnglePos([]option.RangeVal)	Set range for random graphic angles
slide.WithGenGraphNumber(val int)	Set number of graphics
slide.WithEnableGraphVerticalRandom(val bool)	Enable/disable random vertical graphic sorting
slide.WithRangeDeadZoneDirections(val []DeadZoneDirectionType)	Set dead zone directions for puzzle pieces

Set Resources

builder.SetResources(slide.WithXxx(), ...)

Options	Desc
slide.WithBackgrounds([]image.Image)	Set main image backgrounds
slide.WithGraphImages(images []*GraphImage)	Set puzzle piece graphics

Captcha Data

captData, err := capt.Generate()

Method	Desc
GetData() *Block	Get verification data
GetMasterImage() imagedata.JPEGImageData	Get main image
GetTileImage() imagedata.PNGImageData	Get tile image

Validate the captcha

ok := slide.Validate(srcX, srcY, X, Y, paddingValue)

Params	Desc
srcX	User X-axis
srcY	User Y-axis
X	X-axis
Y	Y-axis
paddingValue	Set the padding value

Notes

Puzzle piece image resources (OverlayImage, ShadowImage, MaskImage) must be valid, otherwise ImageTypeErr, ShadowImageTypeErr, or MaskImageTypeErr will be triggered.
Background images must not be empty, otherwise EmptyBackgroundImageErr will be triggered.
In Basic Mode, the puzzle piece’s Y-coordinate is fixed; in Drag Mode, the Y-coordinate can vary based on rangeDeadZoneDirections.
Drag Mode is suitable for scenarios requiring higher interaction freedom but may increase user operation time.

🖖 Rotate CAPTCHA

The Rotate CAPTCHA requires users to rotate a thumbnail to align with the main image’s angle, suitable for intuitive interaction scenarios.

How It Works

Generate Main Image (masterImage): Contains a rotated background image, typically in PNG format.
Generate Thumbnail (thumbImage): Cropped from the main image with circular cropping and transparency effects, typically in PNG format.
User Interaction: Users rotate the thumbnail to the target angle (block.Angle), and the frontend captures the rotation angle.
Verification Logic: The backend compares the user’s rotation angle with the target angle to verify a match.

Code Example

package main

import (
	"encoding/json"
	"fmt"
	"image"
	"log"
	"io/ioutil"

	"github.com/wenlng/go-captcha/v2/rotate"
	"github.com/wenlng/go-captcha/v2/base/codec"
)

var rotateCapt rotate.Captcha

func init() {
	builder := rotate.NewBuilder()

	// You can use preset material resources：https://github.com/wenlng/go-captcha-assets
	bgImage, err := loadPng("../resources/bg.png")
	if err != nil {
		log.Fatalln(err)
	}

	bgImage1, err := loadPng("../resources/bg1.png")
	if err != nil {
		log.Fatalln(err)
	}

	builder.SetResources(
		rotate.WithImages([]image.Image{
			bgImage,
			bgImage1,
		}),
	)

	rotateCapt = builder.Make()
}

func main() {
	captData, err := rotateCapt.Generate()
	if err != nil {
		log.Fatalln(err)
	}

	blockData := captData.GetData()
	if blockData == nil {
		log.Fatalln(">>>>> generate err")
	}

	block, _ := json.Marshal(blockData)
	fmt.Println(">>>>>", string(block))

	var mBase64, tBase64 string
	mBase64, err = captData.GetMasterImage().ToBase64()
	if err != nil {
		fmt.Println(err)
	}
	tBase64, err = captData.GetThumbImage().ToBase64()
	if err != nil {
		fmt.Println(err)
	}

	fmt.Println(">>>>> ", mBase64)
	fmt.Println(">>>>> ", tBase64)
	
	//err = captData.GetMasterImage().SaveToFile("../resources/master.png")
	//if err != nil {
	//	fmt.Println(err)
	//}
	//err = captData.GetThumbImage().SaveToFile("../resources/thumb.png")
	//if err != nil {
	//	fmt.Println(err)
	//}
}

func loadPng(p string) (image.Image, error) {
	imgBytes, err := ioutil.ReadFile(p)
	if err != nil {
		return nil, err
	}
	return codec.DecodeByteToPng(imgBytes)
}

Make Instance

builder.Make()

Configuration Options

rotate.NewBuilder(rotate.WithXxx(), ...) OR builder.SetOptions(rotate.WithXxx(), ...)

Options	Desc
rotate.WithImageSquareSize(val int)	Set main image size, default 220x220
rotate.WithRangeAnglePos(vals []option.RangeVal)	Set range for random verification angles
rotate.WithRangeThumbImageSquareSize(val []int)	Set thumbnail size
rotate.WithThumbImageAlpha(val float32)	Set thumbnail transparency

Set Resources

builder.SetResources(rotate.WithXxx(), ...)

Options	Desc
rotate.WithImages([]image.Image)	Set main image backgrounds

Captcha Data

captData, err := capt.Generate()

Method	Desc
GetData() *Block	Get verification data
GetMasterImage() imagedata.PNGImageData	Get main image
GetThumbImage() imagedata.PNGImageData	Get thumbnail

Validate the captcha

ok := rotate.Validate(srcAngle, angle, paddingValue)

Params	Desc
srcAngle	User Angle
angle	Angle
paddingValue	Set the padding value

Notes

Background images must not be empty, otherwise EmptyImageErr will be triggered.
Ensure background images are valid image.Image types, otherwise ImageTypeErr will be triggered.
Thumbnails are automatically cropped with a circular effect; ensure background images have sufficient resolution to avoid blurriness.

Captcha Image Data

Object Method Of JPEGImageData

Method	Desc
Get() image.Image
ToBytes() ([]byte, error)
ToBytesWithQuality(imageQuality int) ([]byte, error)
ToBase64() (string, error)
ToBase64Data() (string, error)
ToBase64WithQuality(imageQuality int) (string, error)
ToBase64DataWithQuality(imageQuality int) (string, error)
SaveToFile(filepath string, quality int) error

Object Method Of PNGImageData

Method	Desc
Get() image.Image
ToBytes() ([]byte, error)
ToBase64() (string, error)
ToBase64Data() (string, error)
SaveToFile(filepath string) error

Language Support

Web

App

Deployment Service

Binary Program
Docker Image
...

LICENSE

Go Captcha source code is licensed under the Apache Licence, Version 2.0 http://www.apache.org/licenses/LICENSE-2.0.html

Name		Name	Last commit message	Last commit date
Latest commit History 33 Commits
v2		v2
.gitattributes		.gitattributes
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md
README_zh.md		README_zh.md
go.mod		go.mod
go.sum		go.sum

License

wenlng/go-captcha

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GoCaptcha

Ecosystem

Core Features

CAPTCHA Types

Install

Import Module

🖖 Click CAPTCHA

How It Works

Code Example

Make Instance

Configuration Options

Set Resources

Captcha Data

Validate the captcha

Notes

🖖 Slide Or Drag-Drop CAPTCHA

How It Works

Code Example

Make Instance

Configuration Options

Set Resources

Captcha Data

Validate the captcha

Notes

🖖 Rotate CAPTCHA

How It Works

Code Example

Make Instance

Configuration Options

Set Resources

Captcha Data

Validate the captcha

Notes

Captcha Image Data

Object Method Of JPEGImageData

Object Method Of PNGImageData

Language Support

Web

App

Deployment Service

LICENSE

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