Package io.github.pratiyush.totp

Class QRCodeGenerator

java.lang.Object

io.github.pratiyush.totp.QRCodeGenerator

public final class QRCodeGenerator
extends Object

Generates QR codes for TOTP secrets compatible with authenticator apps.

This class creates QR codes containing otpauth:// URIs that can be scanned by Google Authenticator, Microsoft Authenticator, and other compatible apps.

Dependencies

Requires ZXing library (optional dependency). If ZXing is not available, methods will throw NoClassDefFoundError.

Usage Examples

 // Generate QR code as BufferedImage
 BufferedImage qr = QRCodeGenerator.generateImage(
         secret, "user@example.com", "MyApp", 250);
 
 // Save to file
 QRCodeGenerator.saveToFile(secret, "user@example.com", "MyApp",
         Path.of("qr.png"), 250);
 
 // Get as Base64 for embedding in HTML
 String base64 = QRCodeGenerator.generateBase64(
         secret, "user@example.com", "MyApp", 250);
 String html = "<img src='data:image/png;base64," + base64 + "'/>";
 

otpauth URI Format

Generated URIs follow the format:

 
 otpauth://totp/{issuer}:{account}?secret={secret}&issuer={issuer}&algorithm={algo}&digits={digits}&period={period}
 
 

See Also:

• Key URI Format

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_SIZE	Default QR code size in pixels
static final int	MAX_SIZE	Maximum QR code size in pixels
static final int	MIN_SIZE	Minimum QR code size in pixels

Method Summary

Modifier and Type	Method	Description
static String	buildOtpauthUri(String secret, String account, String issuer)	Builds an otpauth URI with default configuration.
static String	buildOtpauthUri(String secret, String account, String issuer, TOTPConfig config)	Builds an otpauth URI for TOTP.
static String	generateBase64(String secret, String account, String issuer, int size)	Generates a QR code as Base64 encoded PNG.
static String	generateBase64(String secret, String account, String issuer, int size, TOTPConfig config)	Generates a QR code as Base64 encoded PNG with custom configuration.
static String	generateDataUri(String secret, String account, String issuer, int size)	Generates a data URI for embedding in HTML.
static BufferedImage	generateImage(String secret, String account, String issuer, int size)	Generates a QR code image.
static BufferedImage	generateImage(String secret, String account, String issuer, int size, TOTPConfig config)	Generates a QR code image with custom configuration.
static void	saveToFile(String secret, String account, String issuer, Path path, int size)	Saves a QR code to a file.
static void	saveToFile(String secret, String account, String issuer, Path path, int size, TOTPConfig config)	Saves a QR code to a file with custom configuration.
static void	writeTo(String secret, String account, String issuer, OutputStream out, String format, int size)	Writes a QR code to an output stream.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_SIZE

public static final int DEFAULT_SIZE

Default QR code size in pixels

See Also:

• Constant Field Values

MIN_SIZE

public static final int MIN_SIZE

Minimum QR code size in pixels

See Also:

• Constant Field Values

MAX_SIZE

public static final int MAX_SIZE

Maximum QR code size in pixels

See Also:

• Constant Field Values

Method Details

buildOtpauthUri

public static String buildOtpauthUri(String secret,
 String account,
 String issuer,
 TOTPConfig config)
                              throws TOTPException

Builds an otpauth URI for TOTP.

Parameters:

secret - the Base32 encoded secret

account - the account name (typically email)

issuer - the service name

config - optional configuration (null for defaults)

Returns:

the otpauth URI

Throws:

TOTPException - if parameters are invalid

buildOtpauthUri

public static String buildOtpauthUri(String secret,
 String account,
 String issuer)
                              throws TOTPException

Builds an otpauth URI with default configuration.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

Returns:

the otpauth URI

Throws:

TOTPException - if parameters are invalid

generateImage

public static BufferedImage generateImage(String secret,
 String account,
 String issuer,
 int size)
                                   throws TOTPException

Generates a QR code image.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

size - the image size in pixels

Returns:

the QR code as BufferedImage

Throws:

TOTPException - if generation fails

generateImage

public static BufferedImage generateImage(String secret,
 String account,
 String issuer,
 int size,
 TOTPConfig config)
                                   throws TOTPException

Generates a QR code image with custom configuration.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

size - the image size in pixels

config - optional TOTP configuration

Returns:

the QR code as BufferedImage

Throws:

TOTPException - if generation fails

generateBase64

public static String generateBase64(String secret,
 String account,
 String issuer,
 int size)
                             throws TOTPException

Generates a QR code as Base64 encoded PNG.

The result can be used directly in HTML img tags:

 <img src="data:image/png;base64,{result}" />
 

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

size - the image size in pixels

Returns:

Base64 encoded PNG

Throws:

TOTPException - if generation fails

generateBase64

public static String generateBase64(String secret,
 String account,
 String issuer,
 int size,
 TOTPConfig config)
                             throws TOTPException

Generates a QR code as Base64 encoded PNG with custom configuration.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

size - the image size in pixels

config - optional TOTP configuration

Returns:

Base64 encoded PNG

Throws:

TOTPException - if generation fails

generateDataUri

public static String generateDataUri(String secret,
 String account,
 String issuer,
 int size)
                              throws TOTPException

Generates a data URI for embedding in HTML.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

size - the image size in pixels

Returns:

data URI (data:image/png;base64,...)

Throws:

TOTPException - if generation fails

saveToFile

public static void saveToFile(String secret,
 String account,
 String issuer,
 Path path,
 int size)
                       throws TOTPException

Saves a QR code to a file.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

path - the file path

size - the image size in pixels

Throws:

TOTPException - if generation or writing fails

saveToFile

public static void saveToFile(String secret,
 String account,
 String issuer,
 Path path,
 int size,
 TOTPConfig config)
                       throws TOTPException

Saves a QR code to a file with custom configuration.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

path - the file path

size - the image size in pixels

config - optional TOTP configuration

Throws:

TOTPException - if generation or writing fails

writeTo

public static void writeTo(String secret,
 String account,
 String issuer,
 OutputStream out,
 String format,
 int size)
                    throws TOTPException

Writes a QR code to an output stream.

Parameters:

secret - the Base32 encoded secret

account - the account name

issuer - the service name

out - the output stream

format - the image format (PNG, JPEG, etc.)

size - the image size in pixels

Throws:

TOTPException - if generation or writing fails