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NFIQ2 uses a custom exception class for error handling that extends std::exception. All exceptions thrown from NFIQ2 functions use this exception type.

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NFIQ2::Exception Class

Exceptions thrown from NFIQ2 functions. 
class NFIQ2::Exception : public std::exception

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Constructors

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Exception(ErrorCode)

Constructor that supplies a default error description. 
Exception(const NFIQ2::ErrorCode errorCode)
Parameters:
  • errorCode - Code that broadly describes the type of error
Example: 
throw NFIQ2::Exception(NFIQ2::ErrorCode::BadArguments);

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Exception(ErrorCode, string)

Constructor that relies on a developer-provided error description. 
Exception(
    const NFIQ2::ErrorCode errorCode,
    const std::string &errorMessage
)
Parameters:
  • errorCode - Code that broadly describes the type of error
  • errorMessage - Description of what happened
Example: 
throw NFIQ2::Exception(
    NFIQ2::ErrorCode::InvalidImageSize,
    "Image dimensions must be at least 100x100 pixels"
);

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Methods

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what()

Extracts thrown exception error message string. 
virtual const char* what() const noexcept override
Returns: The exception message Example: 
try {
    // NFIQ2 operations
} catch (const NFIQ2::Exception &e) {
    std::cerr << "Error: " << e.what() << std::endl;
}

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getErrorCode()

Obtain the code that broadly describes the type of error. 
NFIQ2::ErrorCode getErrorCode() const
Returns: Code that broadly describes the type of error Example: 
try {
    // NFIQ2 operations
} catch (const NFIQ2::Exception &e) {
    if (e.getErrorCode() == NFIQ2::ErrorCode::InvalidImageSize) {
        // Handle invalid image size
    }
}

​
getErrorMessage()

Obtain a description of what happened. 
std::string getErrorMessage() const
Returns: Description of what happened Example: 
try {
    // NFIQ2 operations
} catch (const NFIQ2::Exception &e) {
    std::string msg = e.getErrorMessage();
    // Log or display error message
}

​
defaultErrorMessage() (static)

Obtain a default error message for a given ErrorCode. 
static std::string defaultErrorMessage(
    const NFIQ2::ErrorCode errorCode
)
Parameters:
  • errorCode - Error code from ErrorCode enum
Returns: String containing default description of errorCode Example: 
std::string msg = NFIQ2::Exception::defaultErrorMessage(
    NFIQ2::ErrorCode::BadArguments
);

​
ErrorCode Enum

Error codes used within the NFIQ2 namespace. 
enum class NFIQ2::ErrorCode

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Error Code Values

ValueDescription
UnknownErrorAn unknown or unspecified error occurred
NotEnoughMemoryInsufficient memory available for the operation
BadArgumentsInvalid or malformed arguments provided
QualityMeasureCalculationErrorError during quality measure calculation
CannotWriteToFileUnable to write data to file
CannotReadFromFileUnable to read data from file
NoDataAvailableRequired data is not available
CannotDecodeBase64Failed to decode Base64-encoded data
InvalidConfigurationInvalid or malformed configuration
MachineLearningErrorError in machine learning operations
FJFX_CannotCreateContextFingerJet FX context creation failed
FJFX_CannotCreateFeatureSetFingerJet FX feature set creation failed
FJFX_NoFeatureSetCreatedNo FingerJet FX feature set was created
InvalidUnifiedQualityScoreInvalid unified quality score value
InvalidImageSizeImage dimensions are invalid

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Usage Examples

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Basic Exception Handling

#include <nfiq2_algorithm.hpp>
#include <iostream>

try {
    NFIQ2::Algorithm algorithm;
    auto result = algorithm.computeQualityScore(rawImage);
    std::cout << "Quality Score: " << result.getQualityScore() << std::endl;
} catch (const NFIQ2::Exception &e) {
    std::cerr << "NFIQ2 Error: " << e.what() << std::endl;
    return EXIT_FAILURE;
}

​
Handling Specific Error Codes

try {
    NFIQ2::Algorithm algorithm;
    auto result = algorithm.computeQualityScore(rawImage);
} catch (const NFIQ2::Exception &e) {
    switch (e.getErrorCode()) {
        case NFIQ2::ErrorCode::InvalidImageSize:
            std::cerr << "Invalid image dimensions" << std::endl;
            break;
        case NFIQ2::ErrorCode::BadArguments:
            std::cerr << "Invalid arguments provided" << std::endl;
            break;
        case NFIQ2::ErrorCode::NotEnoughMemory:
            std::cerr << "Out of memory" << std::endl;
            break;
        default:
            std::cerr << "Error: " << e.what() << std::endl;
            break;
    }
}

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Custom Error Messages

void validateImage(const NFIQ2::FingerprintImageData &image) {
    if (image.width < 100 || image.height < 100) {
        throw NFIQ2::Exception(
            NFIQ2::ErrorCode::InvalidImageSize,
            "Image dimensions must be at least 100x100 pixels. "
            "Got " + std::to_string(image.width) + "x" + 
            std::to_string(image.height)
        );
    }
}

​
Getting Default Messages

for (auto code : {
    NFIQ2::ErrorCode::BadArguments,
    NFIQ2::ErrorCode::InvalidImageSize,
    NFIQ2::ErrorCode::NotEnoughMemory
}) {
    std::cout << "Error code default message: "
              << NFIQ2::Exception::defaultErrorMessage(code)
              << std::endl;
}

​
Source Reference

Defined in: NFIQ2/NFIQ2Algorithm/include/nfiq2_exception.hpp

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