从回调函数的参数中获取值
Get value from the parameter of a callback function
我正在使用 biometrics SDK。我将 headers 转换为 delphi 以使用 dll。
看起来像这样：
const
{VrBio_EventType}
VRBIO_CAPTURE_EVENT_UNPLUG = [=10=]1; {Fingerprint scanner unplugged from the computer.}
VRBIO_CAPTURE_EVENT_PLUG = [=10=]2; {Fingerprint scanner plugged on the computer.}
VRBIO_CAPTURE_EVENT_REMOVED = [=10=]4; {Finger removed from the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_PLACED = [=10=]8; {Finger placed on the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_IMAGE_FRAME = ; {A fingerprint frame was captured on the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_IMAGE_CAPTURED = 0; {A fingerprint image was captured on the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_FAKE_FINGER_DETECTED = 0; {A false finger has been detected on the sensor}
VRBIO_CAPTURE_EVENT_FAKE_FINGER_REMOVED = 0; {A false finger has been removed from the sensor}
type
(* Stores the parameters of the ISO 19794-4 image format. @see VGetReaderProperties @see VrBio_ReaderProperty
typedef struct
{
/** @see VrBio_ISO197944CompressionMode*/
int compressionMode;
/** @see VrBio_ISO197944ImpressionType*/
int impressionType;
/** @see VrBio_ISO197944FingerPosition*/
int fingerPosition;
}VrBio_ISO197944Parameters;
*)
PISO197944Parameters = ^TISO197944Parameters;
TISO197944Parameters = record
compressionMode: Integer; { @see VrBio_ISO197944CompressionMode}
impressionType: Integer; { @see VrBio_ISO197944ImpressionType}
fingerPosition: Integer; { @see VrBio_ISO197944FingerPosition}
end;
(* Represents a biometric image. @see VrBio_CaptureEventCallback \ref VSyncCapture
struct VrBio_BiometricImage
{
/** Image width.*/
int width;
/**Image height*/
int height;
/**Image resolution in dpi. For the obsolete functions, use pixels/cm.*/
int resolution;
/**Number of channels in the image. Fingerprint images should always be grayscale, so this value is always 1.*/
int channels;
/**Biometric modality.
* Always use VRBIO_BIOMETRIC_MODALITY_FINGERPRINT.
* \ref VrBio_BiometricModality.
*/
int biometricModality;
/**Scanner type.
* \ref VrBio_ScannerType.
*/
int scannerType;
/**Formato de imagem: Formato da imagem.
*\ ref VrBio_ImageFormat.*/
int imageFormat;
/**Size of the buffer*/
int bufferSize;
/**Compression rate. Valid for images that allow compression.
* \ref VrBio_CompressionRate
*/
int compressionRate;
/**Quality of the fingerprint image.
* \ref VrBio_FingerQuality
*/
int fingerQuality;
/** Only valid if the image if imageFormat is \ref VrBio_ImageFormat::VRBIO_IMAGEFORMAT_ISO19794_4
*\ref VrBio_ISO197944Parameters
*/
VrBio_ISO197944Parameters* ISO197944_parameters;
/** Buffer storing the pixels of the image.
The position(x,y,c) of a pixel is y*width*channels+x*channels+c.
*/
unsigned char* buffer;
/**Reserved for future use*/
void* reserved;
};
typedef struct VrBio_BiometricImage VrBio_BiometricImage;
*)
PBiometricImage = ^TBiometricImage;
TBiometricImage = record
width: Integer; { Image width. }
height: Integer; { Image height }
resolution: Integer; { Image resolution in dpi. For the obsolete functions, use pixels/cm.}
channels: Integer; { Number of channels in the image. Fingerprint images should always be grayscale, so this value is always 1. }
biometricModality: Integer; { Biometric modality. Always use VRBIO_BIOMETRIC_MODALITY_FINGERPRINT. \ref VrBio_BiometricModality. }
scannerType: Integer; { Scanner type. \ref VrBio_ScannerType. }
imageFormat: Integer; { Formato de imagem: Formato da imagem. \ ref VrBio_ImageFormat. }
bufferSize: Integer; { Size of the buffer }
compressionRate: Integer; { Compression rate. Valid for images that allow compression. \ref VrBio_CompressionRate }
fingerQuality: Integer; { Quality of the fingerprint image. \ref VrBio_FingerQuality }
ISO197944_parameters: PISO197944Parameters; { Only valid if the image if imageFormat is \ref VrBio_ImageFormat::VRBIO_IMAGEFORMAT_ISO19794_4 \ref VrBio_ISO197944Parameters }
buffer: PByte; { Buffer storing the pixels of the image. The position(x,y,c) of a pixel is y*width*channels+x*channels+c. }
reserved: Pointer; { Reserved for future use }
end;
(*
#include "VTypes.h"
#ifdef WIN32
#define DLLIMPORT extern "C" __declspec(dllimport) int __stdcall
#else
#define DLLIMPORT extern "C"
#endif
*)
{ Callback function that receives events..
typedef void (*VrBio_CaptureEventCallback) (
int eventType,
const char* readerName,
VrBio_BiometricImage* image,
const void* userData)
}
TCaptureEventCallback = procedure(eventType: Integer; readerName: PAnsiChar; image: PBiometricImage; userData: Pointer); stdcall;
{ Function responsible for initializing the SDK. This function MUST be called before calling any other method, except \ref VInstallLicense
DLLIMPORT VStartSDK(VrBio_CaptureEventCallback eventCallback);
}
function VStartSDK(eventCallback: TCaptureEventCallback): Integer; stdcall;
{ Function responsible for finalizing the SDK. This function should be called when the SDK is not needed in the application anymore.
DLLIMPORT VStopSDK();
}
function VStopSDK(): Integer; stdcall;
{ Function responsible for starting the capture on a specific fingerprint reader.
After calling this function, the application is able to receive events.
DLLIMPORT VStartReader(const char* readerName);
}
function VStartReader(readerName: PAnsiChar): Integer; stdcall;
使用方法如下：
implementation
{$R *.dfm}
procedure EventCallback(eventType: Integer; readerName: PAnsiChar; image: PBiometricImage; userData: Pointer); stdcall;
begin
case eventType of
VRBIO_CAPTURE_EVENT_UNPLUG: Form1.Memo1.Lines.Add('Leitor desconectado!');
VRBIO_CAPTURE_EVENT_REMOVED: Form1.Memo1.Lines.Add('Dedo removido!');
VRBIO_CAPTURE_EVENT_PLACED: Form1.Memo1.Lines.Add('Dedo detectado!');
VRBIO_CAPTURE_EVENT_IMAGE_FRAME: Form1.Memo1.Lines.Add('Frame capturado!');
VRBIO_CAPTURE_EVENT_IMAGE_CAPTURED: Form1.Memo1.Lines.Add('Imagem capturada!');
VRBIO_CAPTURE_EVENT_FAKE_FINGER_DETECTED: Form1.Memo1.Lines.Add('Dedo falso detectado!');
VRBIO_CAPTURE_EVENT_FAKE_FINGER_REMOVED: Form1.Memo1.Lines.Add('Dedo falso removido!');
VRBIO_CAPTURE_EVENT_PLUG:
begin
VStartReader(readerName);
Form1.Memo1.Lines.Add('Leitor conectado!');
end;
end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
VStartSDK(EventCallback);
end;
我的问题：
我可以使用该应用程序并获取 Plug、Unplug 和 Placed 事件，但是当我获取 Image Captured 事件时，我有访问权限。
在正在运行的事件中，EventCallback 参数图像是 nil。 TBiometricImage记录转换是否正确？
如何将 TBiometricImage 缓冲区转换为 TBitmap 并在 TImage 中显示捕获的图像？
when I get the Image Captured event I have an acces vilation. In the events that are working the EventCallback parameter image is nil. Is the TBiometricImage record conversion correct?
各个字段声明正常，但请仔细检查您的 Delphi 记录的对齐方式和填充是否与 C/C++ 中的结构使用的相同对齐方式和填充相匹配。
此外，更重要的是，C/C++ 中的 VrBio_CaptureEventCallback typedef 声明时没有指定任何调用约定，因此它将使用编译器的默认约定，通常是 __cdecl而不是 __stdcall（可以在编译器设置中配置）。在 Delphi 中，您声明 TCaptureEventCallback 使用 stdcall 而不是 cdecl。您必须确保正确匹配调用约定（导出的 DLL 函数确实使用 stdcall，所以您没问题）。
How can I convert the TBiometricImage buffer to a TBitmap and display the captured image in a TImage?
SDK 文档没有解释如何处理各种图像格式。但是，只看结构声明，buffer 字段指向实际图像数据，imageFormat 字段指示该数据的格式（有一个 VrBio_ImageFormat 枚举尚未翻译）。因此，您必须先查看 imageFormat 才能知道如何解释 buffer.
我确实看到 VConvertImage() 功能可用。所以你应该能够将图像转换为 BMP 格式，如果它们还没有的话。根据 SDK 中的示例，看起来 buffer 数据 可能 是标准 BMP 文件格式，因此您可以尝试将 buffer 复制到 TMemoryStream 然后使用 TBitmap.LoadFromStream() 方法。
还有 GIF 和 JPG 图像格式可用，可以分别由 TGIFImage 和 TJPEGImage 处理，甚至 TWICImage，如果你想显示扫描的 GIF/JPG 图像而无需先将它们转换为 BMP。还有一种 RAW 图像格式可用（显然你的图像正在使用），但没有标准的 VCL TGraphic class 来处理 RAW 图像，但我认为可能有一些第 3 方 class如果你环顾四周，就会四处漂浮。
否则，如果需要，您可以尝试将图像数据转换为 BMP，然后将 buffer 传递给 Win32 API CreateBitmap/Indirect() 或 CreateDibSection() 函数，如果成功，然后将结果 HBITMAP 分配给 TBitmap.Handle 属性。
我正在使用 biometrics SDK。我将 headers 转换为 delphi 以使用 dll。
看起来像这样：
const
{VrBio_EventType}
VRBIO_CAPTURE_EVENT_UNPLUG = [=10=]1; {Fingerprint scanner unplugged from the computer.}
VRBIO_CAPTURE_EVENT_PLUG = [=10=]2; {Fingerprint scanner plugged on the computer.}
VRBIO_CAPTURE_EVENT_REMOVED = [=10=]4; {Finger removed from the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_PLACED = [=10=]8; {Finger placed on the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_IMAGE_FRAME = ; {A fingerprint frame was captured on the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_IMAGE_CAPTURED = 0; {A fingerprint image was captured on the fingerprint scanner.}
VRBIO_CAPTURE_EVENT_FAKE_FINGER_DETECTED = 0; {A false finger has been detected on the sensor}
VRBIO_CAPTURE_EVENT_FAKE_FINGER_REMOVED = 0; {A false finger has been removed from the sensor}
type
(* Stores the parameters of the ISO 19794-4 image format. @see VGetReaderProperties @see VrBio_ReaderProperty
typedef struct
{
/** @see VrBio_ISO197944CompressionMode*/
int compressionMode;
/** @see VrBio_ISO197944ImpressionType*/
int impressionType;
/** @see VrBio_ISO197944FingerPosition*/
int fingerPosition;
}VrBio_ISO197944Parameters;
*)
PISO197944Parameters = ^TISO197944Parameters;
TISO197944Parameters = record
compressionMode: Integer; { @see VrBio_ISO197944CompressionMode}
impressionType: Integer; { @see VrBio_ISO197944ImpressionType}
fingerPosition: Integer; { @see VrBio_ISO197944FingerPosition}
end;
(* Represents a biometric image. @see VrBio_CaptureEventCallback \ref VSyncCapture
struct VrBio_BiometricImage
{
/** Image width.*/
int width;
/**Image height*/
int height;
/**Image resolution in dpi. For the obsolete functions, use pixels/cm.*/
int resolution;
/**Number of channels in the image. Fingerprint images should always be grayscale, so this value is always 1.*/
int channels;
/**Biometric modality.
* Always use VRBIO_BIOMETRIC_MODALITY_FINGERPRINT.
* \ref VrBio_BiometricModality.
*/
int biometricModality;
/**Scanner type.
* \ref VrBio_ScannerType.
*/
int scannerType;
/**Formato de imagem: Formato da imagem.
*\ ref VrBio_ImageFormat.*/
int imageFormat;
/**Size of the buffer*/
int bufferSize;
/**Compression rate. Valid for images that allow compression.
* \ref VrBio_CompressionRate
*/
int compressionRate;
/**Quality of the fingerprint image.
* \ref VrBio_FingerQuality
*/
int fingerQuality;
/** Only valid if the image if imageFormat is \ref VrBio_ImageFormat::VRBIO_IMAGEFORMAT_ISO19794_4
*\ref VrBio_ISO197944Parameters
*/
VrBio_ISO197944Parameters* ISO197944_parameters;
/** Buffer storing the pixels of the image.
The position(x,y,c) of a pixel is y*width*channels+x*channels+c.
*/
unsigned char* buffer;
/**Reserved for future use*/
void* reserved;
};
typedef struct VrBio_BiometricImage VrBio_BiometricImage;
*)
PBiometricImage = ^TBiometricImage;
TBiometricImage = record
width: Integer; { Image width. }
height: Integer; { Image height }
resolution: Integer; { Image resolution in dpi. For the obsolete functions, use pixels/cm.}
channels: Integer; { Number of channels in the image. Fingerprint images should always be grayscale, so this value is always 1. }
biometricModality: Integer; { Biometric modality. Always use VRBIO_BIOMETRIC_MODALITY_FINGERPRINT. \ref VrBio_BiometricModality. }
scannerType: Integer; { Scanner type. \ref VrBio_ScannerType. }
imageFormat: Integer; { Formato de imagem: Formato da imagem. \ ref VrBio_ImageFormat. }
bufferSize: Integer; { Size of the buffer }
compressionRate: Integer; { Compression rate. Valid for images that allow compression. \ref VrBio_CompressionRate }
fingerQuality: Integer; { Quality of the fingerprint image. \ref VrBio_FingerQuality }
ISO197944_parameters: PISO197944Parameters; { Only valid if the image if imageFormat is \ref VrBio_ImageFormat::VRBIO_IMAGEFORMAT_ISO19794_4 \ref VrBio_ISO197944Parameters }
buffer: PByte; { Buffer storing the pixels of the image. The position(x,y,c) of a pixel is y*width*channels+x*channels+c. }
reserved: Pointer; { Reserved for future use }
end;
(*
#include "VTypes.h"
#ifdef WIN32
#define DLLIMPORT extern "C" __declspec(dllimport) int __stdcall
#else
#define DLLIMPORT extern "C"
#endif
*)
{ Callback function that receives events..
typedef void (*VrBio_CaptureEventCallback) (
int eventType,
const char* readerName,
VrBio_BiometricImage* image,
const void* userData)
}
TCaptureEventCallback = procedure(eventType: Integer; readerName: PAnsiChar; image: PBiometricImage; userData: Pointer); stdcall;
{ Function responsible for initializing the SDK. This function MUST be called before calling any other method, except \ref VInstallLicense
DLLIMPORT VStartSDK(VrBio_CaptureEventCallback eventCallback);
}
function VStartSDK(eventCallback: TCaptureEventCallback): Integer; stdcall;
{ Function responsible for finalizing the SDK. This function should be called when the SDK is not needed in the application anymore.
DLLIMPORT VStopSDK();
}
function VStopSDK(): Integer; stdcall;
{ Function responsible for starting the capture on a specific fingerprint reader.
After calling this function, the application is able to receive events.
DLLIMPORT VStartReader(const char* readerName);
}
function VStartReader(readerName: PAnsiChar): Integer; stdcall;
使用方法如下：
implementation
{$R *.dfm}
procedure EventCallback(eventType: Integer; readerName: PAnsiChar; image: PBiometricImage; userData: Pointer); stdcall;
begin
case eventType of
VRBIO_CAPTURE_EVENT_UNPLUG: Form1.Memo1.Lines.Add('Leitor desconectado!');
VRBIO_CAPTURE_EVENT_REMOVED: Form1.Memo1.Lines.Add('Dedo removido!');
VRBIO_CAPTURE_EVENT_PLACED: Form1.Memo1.Lines.Add('Dedo detectado!');
VRBIO_CAPTURE_EVENT_IMAGE_FRAME: Form1.Memo1.Lines.Add('Frame capturado!');
VRBIO_CAPTURE_EVENT_IMAGE_CAPTURED: Form1.Memo1.Lines.Add('Imagem capturada!');
VRBIO_CAPTURE_EVENT_FAKE_FINGER_DETECTED: Form1.Memo1.Lines.Add('Dedo falso detectado!');
VRBIO_CAPTURE_EVENT_FAKE_FINGER_REMOVED: Form1.Memo1.Lines.Add('Dedo falso removido!');
VRBIO_CAPTURE_EVENT_PLUG:
begin
VStartReader(readerName);
Form1.Memo1.Lines.Add('Leitor conectado!');
end;
end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
VStartSDK(EventCallback);
end;
我的问题：
我可以使用该应用程序并获取 Plug、Unplug 和 Placed 事件，但是当我获取 Image Captured 事件时，我有访问权限。
在正在运行的事件中，EventCallback 参数图像是 nil。 TBiometricImage记录转换是否正确？
如何将 TBiometricImage 缓冲区转换为 TBitmap 并在 TImage 中显示捕获的图像？
when I get the Image Captured event I have an acces vilation. In the events that are working the EventCallback parameter image is nil. Is the TBiometricImage record conversion correct?
各个字段声明正常，但请仔细检查您的 Delphi 记录的对齐方式和填充是否与 C/C++ 中的结构使用的相同对齐方式和填充相匹配。
此外，更重要的是，C/C++ 中的 VrBio_CaptureEventCallback typedef 声明时没有指定任何调用约定，因此它将使用编译器的默认约定，通常是 __cdecl而不是 __stdcall（可以在编译器设置中配置）。在 Delphi 中，您声明 TCaptureEventCallback 使用 stdcall 而不是 cdecl。您必须确保正确匹配调用约定（导出的 DLL 函数确实使用 stdcall，所以您没问题）。
How can I convert the TBiometricImage buffer to a TBitmap and display the captured image in a TImage?
SDK 文档没有解释如何处理各种图像格式。但是，只看结构声明，buffer 字段指向实际图像数据，imageFormat 字段指示该数据的格式（有一个 VrBio_ImageFormat 枚举尚未翻译）。因此，您必须先查看 imageFormat 才能知道如何解释 buffer.
我确实看到 VConvertImage() 功能可用。所以你应该能够将图像转换为 BMP 格式，如果它们还没有的话。根据 SDK 中的示例，看起来 buffer 数据 可能 是标准 BMP 文件格式，因此您可以尝试将 buffer 复制到 TMemoryStream 然后使用 TBitmap.LoadFromStream() 方法。
还有 GIF 和 JPG 图像格式可用，可以分别由 TGIFImage 和 TJPEGImage 处理，甚至 TWICImage，如果你想显示扫描的 GIF/JPG 图像而无需先将它们转换为 BMP。还有一种 RAW 图像格式可用（显然你的图像正在使用），但没有标准的 VCL TGraphic class 来处理 RAW 图像，但我认为可能有一些第 3 方 class如果你环顾四周，就会四处漂浮。
否则，如果需要，您可以尝试将图像数据转换为 BMP，然后将 buffer 传递给 Win32 API CreateBitmap/Indirect() 或 CreateDibSection() 函数，如果成功，然后将结果 HBITMAP 分配给 TBitmap.Handle 属性。