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画像ファイルからexifメタデータを抜き出す

Posted at 2014-09-09

なんかだか面倒くさいけど、これライブラリないんだろうか。

static NSDictionary *getExifFromData(NSData * const data)
{
    CFStringRef imageSourceOptionKeys[2];
    CFTypeRef imageSourceOptionValues[2];
    imageSourceOptionKeys[0] = kCGImageSourceShouldCache;
    imageSourceOptionValues[0] = kCFBooleanTrue;
    imageSourceOptionKeys[1] = kCGImageSourceShouldAllowFloat;
    imageSourceOptionValues[1] = kCFBooleanTrue;

    CFDictionaryRef imageSourceOptions = CFDictionaryCreate(
            NULL,
            (const void **)imageSourceOptionKeys,
            (const void**)imageSourceOptionValues,
            sizeof(imageSourceOptionKeys) / sizeof(imageSourceOptionKeys[0]),
            &kCFTypeDictionaryKeyCallBacks,
            &kCFTypeDictionaryValueCallBacks);


    CGImageSourceRef imageSourceRef = CGImageSourceCreateWithData((__bridge CFDataRef) data,  imageSourceOptions);
    CFRelease(imageSourceOptions);

    CFDictionaryRef imagePropertiesDictionary = CGImageSourceCopyPropertiesAtIndex(imageSourceRef, 0, NULL);

    NSDictionary *exif = (__bridge NSDictionary *)CFDictionaryGetValue(imagePropertiesDictionary, kCGImagePropertyExifDictionary);

    CFRelease(imageSourceRef);

    return exif;
}

うまくいくと以下の様なメタデータがとれる。

// NSLog("exif: %@, exif);
exif: {
    ColorSpace = 1;
    ComponentsConfiguration =     (
        1,
        2,
        3,
        0
    );
    DateTimeDigitized = "2012:10:15 20:57:48";
    DateTimeOriginal = "2012:10:15 20:57:48";
    ExifVersion =     (
        2,
        2,
        1
    );
    FlashPixVersion =     (
        1,
        0
    );
    PixelXDimension = 1536;
    PixelYDimension = 1536;
    SceneCaptureType = 0;
}

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