如何使用Exif API

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文章信息

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代码示例

源文件: Media:GeoTagging Example.zip

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测试基于

设备:: Nokia N95

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兼容于

平台: S60 3rd Edition, MR

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文章

关键词: CExifRead

翻译:

翻译自: CS000968 - Using Exif API

由 hoolee

最后由 hamishwillee 在 15 Jun 2012 编辑

• 详细描述

CExifRead接口类用来分析Exif v2.2文件格式，用这个API你可以读取JPEG图像的数据，如日期，分辨率，方向，ISO速度，曝光时间等。

MMP文件

需要下列链接库和能力：

CAPABILITY        NONE
LIBRARY           efsrv.lib
LIBRARY           exiflib.lib

头文件

读取Exif数据的类

#include <exifread.h>
#include <f32file.h>
 
class CMyExifReader : public CBase
    {
    public:
        static CMyExifReader* NewL();
        static CMyExifReader* NewLC();
        virtual ~CMyExifReader();
    private:
        CMyExifReader();
        void ConstructL();
    public:
        void ReadExifDataL(TDesC& aFilename);
 
    public:
        HBufC8* iImageDescription;
        HBufC8* iImageDate;
 
    };

源文件

CMyExifReader::CMyExifReader()
    {
    }
 
CMyExifReader* CMyExifReader::NewL()
    {
    CMyExifReader* self = NewLC();
    CleanupStack::Pop();
    return self;
    }
 
CMyExifReader* CMyExifReader::NewLC()
    {
    CMyExifReader* self = new (ELeave) CMyExifReader();
    CleanupStack::PushL( self );
    self->ConstructL();
    return self;
    }
 
void CMyExifReader::ConstructL()
    {
    }
 
CMyExifReader::~CMyExifReader()
    {
    delete iImageDescription;
    delete iImageDate;
    }
 
void CMyExifReader::ReadExifDataL(TDesC& aFilename)
    {
    // 1. Read Exif image from the file to a buffer
    RFile file;
    User::LeaveIfError( file.Open( CEikonEnv::Static()->FsSession(), aFilename, EFileRead ) );
    CleanupClosePushL( file );
    TInt size = 0;
    file.Size(size);
    HBufC8* exif = HBufC8::NewL( size );
    CleanupStack::PushL( exif );
    TPtr8 bufferDes( exif->Des() ); 
    User::LeaveIfError( file.Read( bufferDes ) );
    CleanupStack::Pop( exif );
    CleanupStack::PopAndDestroy(); // file
    CleanupStack::PushL( exif );
 
    // 2. Instantiate Exif reader...
    CExifRead* read = CExifRead::NewL( exif->Des() );
    CleanupStack::PushL( read );
 
    // 3. Get required data from the Exif image...
    TInt err = KErrNone;
    TRAP(err,iImageDescription = read->GetImageDescriptionL());
    TRAP(err,iImageDate = read->GetDateTimeL());
    // TODO: See CExifRead API for getting more data from image
 
    // 4. Delete the reader instance...
    CleanupStack::PopAndDestroy( read );
    CleanupStack::PopAndDestroy( exif );
    }

相关连接

Exif API

File:GeoTagging Example.zip