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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• 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.

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

1. Click CAPTCHA: Users click specified points or characters on the main image, supporting text and graphic modes.
2. Slide CAPTCHA: Users slide a puzzle piece to the correct position on the main image, supporting basic and drag-drop modes.
3. 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.
4. Rotate CAPTCHA: Users rotate a thumbnail to align with the main image’s angle.

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

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

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.

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

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) //} }

• builder.Make()
• builder.MakeShape()

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

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

captData, err := capt.Generate()

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

• 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.

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.

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

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) }

• builder.Make()
• builder.MakeDragDrop()

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

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

captData, err := capt.Generate()

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

• 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.

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

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

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) }

• builder.Make()

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

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

captData, err := capt.Generate()

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

• 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.

• Golang
• NodeJs
• Rust
• Python
• Java
• PHP
• ...

• JavaScript
• Vue
• React
• Angular
• Svelte
• Solid
• ...

• UniApp
• Wx-Applet
• React Native App
• Flutter App
• Android App
• IOS App
• ...

• Binary Program
• Docker Image
• ...

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