GrabbaFingerprintImage Class Reference

Description

Encapsulation of fingerprint image data plus the associated metadata.

Note

All property values are passed by copy; a new copy of the value will be generated each time a property is read.

Thread safety:

• Concurrent accesses to distinct objects: safe
• Concurrent accesses to the same object: unsafe, unless all accesses are read-only (i.e. property reads)

Inheritance diagram for GrabbaFingerprintImage:

Instance Methods
(NSString *_Nonnull)	- generateBase64WithError:
	Encode a fingerprint image as a MIME-compliant Base64 string. More...
(NSData *_Nonnull)	- generateBitmapWithError:
	Attempt to generate a grey-scale bitmap (BMP/DIB format) from the image. More...
(instancetype _Nullable)	- init
	Initialise a null (empty) fingerprint image. More...
(instancetype _Nullable)	- initWithData:type:rows:columns:
	Initialise a fingerprint image with given contents. More...

Class Methods
(instancetype _Nullable)	+ image
	Allocate and initialise a null (empty) fingerprint image. More...
(instancetype _Nullable)	+ imageWithData:type:rows:columns:
	Allocate and initialise a new fingerprint image with given contents. More...
(NSString *_Nonnull)	+ typeNameForID:
	Obtain the name of a given image type ID. More...

Properties
size_t	columns
	Number of pixel columns in the image. More...
NSData *_Nonnull	data
	Contents of the fingerprint image, represented in the specified format. More...
GrabbaFingerprintImageTypeID	imageType
	Type of image data represented by the object. More...
size_t	rows
	Number of pixel rows in the image. More...
NSString *_Nonnull	typeName
	Name of the current image type ID. More...

Method Documentation

generateBase64WithError:()

- (NSString* _Nonnull) generateBase64WithError:

(GrabbaErrorCode *_Nonnull)

error

Encode a fingerprint image as a MIME-compliant Base64 string.

If the supplied error code indicates no prior errors, and the image is not in the V1 compression format, then an attempt will be made to convert the fingerprint image to the BMP (DIB) format as per generateBitmap. The resultant image data is then encoded as a Base64 string, with a suitable MIME type header prepended.

Parameters

error

Error code; operation proceeds only if set to GrabbaNoError. If an error is detected during this operation, then the parameter will be updated with the details.

Returns

Generated encoding if the operation proceeds and is successful; empty string otherwise

generateBitmapWithError:()

- (NSData* _Nonnull) generateBitmapWithError:

(GrabbaErrorCode *_Nonnull)

error

Attempt to generate a grey-scale bitmap (BMP/DIB format) from the image.

If the supplied error code indicates no prior errors, and the image is not in the V1 compression format, then an attempt will be made to convert the supplied fingerprint image to the Microsoft BMP (DIB) format.

Image data for this function is typically taken from the imageEvent callback of a FingerprintListener object.

Note

This decoder has not been FBI-certified, and is not guaranteed to be accurate for the purposes of automatic fingerprint comparison.

Parameters

error

Error code; operation proceeds only if set to GrabbaNoError. If an error is detected during this operation, then the parameter will be updated with the details.

Returns

Generated bitmap file if the operation proceeds and is successful, empty 0x0 bitmap otherwise

image()

+ (instancetype _Nullable) image

Allocate and initialise a null (empty) fingerprint image.

Returns

Pointer to initialised object if initialisation succeeded; nil if it failed

imageWithData:type:rows:columns:()

+ (instancetype _Nullable) imageWithData:		(NSData *_Nonnull)	data
type:		(GrabbaFingerprintImageTypeID)	type
rows:		(size_t)	rows
columns:		(size_t)	columns

Allocate and initialise a new fingerprint image with given contents.

Parameters

data	Initial value of the data field (image data)
type	Initial value of the type field (image type ID)
rows	Initial count of pixel rows in the image
columns	Initial count of pixel columns in the image

Returns

Pointer to initialised object if initialisation succeeded; nil if it failed

init()

- (instancetype _Nullable) init

Initialise a null (empty) fingerprint image.

Returns

Pointer to initialised object if initialisation succeeded; nil if it failed

initWithData:type:rows:columns:()

- (instancetype _Nullable) initWithData:		(NSData *_Nonnull)	data
type:		(GrabbaFingerprintImageTypeID)	type
rows:		(size_t)	rows
columns:		(size_t)	columns

Initialise a fingerprint image with given contents.

Parameters

data	Initial value of the data field (image data)
type	Initial value of the type field (image type ID)
rows	Initial count of pixel rows in the image
columns	Initial count of pixel columns in the image

Returns

Pointer to initialised object if initialisation succeeded; nil if it failed

typeNameForID:()

+ (NSString* _Nonnull) typeNameForID:

(GrabbaFingerprintImageTypeID)

ID

Obtain the name of a given image type ID.

Parameters

ID	The type of image which is being queried

Returns

String representation of given ID if known; empty string if unknown

Property Documentation

columns

- (size_t) columns

readwritenonatomicassign

Number of pixel columns in the image.

data

- (NSData* _Nonnull) data

readwritenonatomiccopy

Contents of the fingerprint image, represented in the specified format.

For uncompressed images this will use a raw 8bpp grayscale format - i.e. one byte per pixel, scanning left to right within each row, and rows ordered from top to bottom. No header or footer data is included.

For images in the V1 or WSQ formats, the specified data format is used; refer to the relevant format specifications for additional details.

imageType

- (GrabbaFingerprintImageTypeID) imageType

readwritenonatomicassign

Type of image data represented by the object.

rows

- (size_t) rows

readwritenonatomicassign

Number of pixel rows in the image.

typeName

- (NSString* _Nonnull) typeName

readnonatomiccopy

Name of the current image type ID.

This value is not directly writeable; updates should use imageType instead