五、CGImageProperties中定义的字典意义
前面提到的CGImageSourceCopyProperties方法与CGImageSourceCopyPropertiesAtIndex方法都会返回一个字典，字典中可能包含如下有意义的键：
//TIFF信息字典
const CFStringRef kCGImagePropertyTIFFDictionary;
/GIF信息字典
const CFStringRef kCGImagePropertyGIFDictionary;
//JFIF信息字典
const CFStringRef kCGImagePropertyJFIFDictionary;
//EXif信息字典
const CFStringRef kCGImagePropertyExifDictionary;
//PNG信息字典
const CFStringRef kCGImagePropertyPNGDictionary;
//IPTC信息字典
const CFStringRef kCGImagePropertyIPTCDictionary;
//GPS信息字典
const CFStringRef kCGImagePropertyGPSDictionary;
//原始信息字典
const CFStringRef kCGImagePropertyRawDictionary;
//CIFF信息字典
const CFStringRef kCGImagePropertyCIFFDictionary;
//佳能相机信息字典
const CFStringRef kCGImagePropertyMakerCanonDictionary;
//尼康相机信息字典
const CFStringRef kCGImagePropertyMakerNikonDictionary;
//柯尼卡相机信息字典
const CFStringRef kCGImagePropertyMakerMinoltaDictionary;
//富士相机信息字典
const CFStringRef kCGImagePropertyMakerFujiDictionary;
//奥林巴斯相机信息字典
const CFStringRef kCGImagePropertyMakerOlympusDictionary;
//宾得相机信息字典
const CFStringRef kCGImagePropertyMakerPentaxDictionary;
//对应Photoshop相片的信息字典
const CFStringRef kCGImageProperty8BIMDictionary;
//NDG信息字典
const CFStringRef kCGImagePropertyDNGDictionary ;
//ExifAux信息字典
const CFStringRef kCGImagePropertyExifAuxDictionary;
//OpenEXR信息字典
const CFStringRef kCGImagePropertyOpenEXRDictionary;
//Apple相机信息字典
const CFStringRef kCGImagePropertyMakerAppleDictionary ;
CGImageSourceCopyProperties方法返回的字典中还可能会有如下一个特殊的键：
//对应文件大小
const CFStringRef kCGImagePropertyFileSize;
CGImageSourceCopyPropertiesAtIndex方法中可能包含的特殊键：
//像素高度
const CFStringRef kCGImagePropertyPixelHeight;
//像素宽度
const CFStringRef kCGImagePropertyPixelWidth;
//DPI高度
const CFStringRef kCGImagePropertyDPIHeight;
//DPI宽度
const CFStringRef kCGImagePropertyDPIWidth;
//颜色位数
const CFStringRef kCGImagePropertyDepth;
//图片的显示方向
/*
对应Number值
* 1 = 左上到右下.
* 2 = 右上到左下.
* 3 = 右下到左上.
* 4 = 左下到右上.
* 5 = 行列置换 左上到右下.
* 6 = 行列置换 右上到左下.
* 7 = 行列置换 右下到左上.
* 8 = 行列置换 左下到右上.
*/
const CFStringRef kCGImagePropertyOrientation;
//颜色是否支持浮点数
const CFStringRef kCGImagePropertyIsFloat;
//图像是否包含像素样本
const CFStringRef kCGImagePropertyIsIndexed;
//图像是否包含alpha通道
const CFStringRef kCGImagePropertyHasAlpha;
//图像的颜色模式
const CFStringRef kCGImagePropertyColorModel;
//嵌入图片的ICC配置文件名称
const CFStringRef kCGImagePropertyProfileName;
kCGImagePropertyColorModel键可返回的值有如下几种定义：
//RBG模式
const CFStringRef kCGImagePropertyColorModelRGB;
//Gray模式
const CFStringRef kCGImagePropertyColorModelGray;
//CMYK模式
const CFStringRef kCGImagePropertyColorModelCMYK;
//Lab模式
const CFStringRef kCGImagePropertyColorModelLab;
kCGImagePropertyTIFFDictionary键可返回的值定义如下：
//图片数据压缩方案
const CFStringRef kCGImagePropertyTIFFCompression;
//图片数据的色彩空间
const CFStringRef kCGImagePropertyTIFFPhotometricInterpretation;
//文档名称
const CFStringRef kCGImagePropertyTIFFDocumentName;
//图片描述
const CFStringRef kCGImagePropertyTIFFImageDescription;
//相机设备名
const CFStringRef kCGImagePropertyTIFFMake;
//相机设备模式
const CFStringRef kCGImagePropertyTIFFModel;
//图片方向
const CFStringRef kCGImagePropertyTIFFOrientation;
//横向每个分辨位的像素数
const CFStringRef kCGImagePropertyTIFFXResolution;
//纵向每个分辨位的像素数
const CFStringRef kCGImagePropertyTIFFYResolution;
//分辨率单位
const CFStringRef kCGImagePropertyTIFFResolutionUnit;
//创建图像的软件名称和版本
const CFStringRef kCGImagePropertyTIFFSoftware;
//transform函数
const CFStringRef kCGImagePropertyTIFFTransferFunction;
//日期时间
const CFStringRef kCGImagePropertyTIFFDateTime;
//作者
const CFStringRef kCGImagePropertyTIFFArtist;
//创建图片的电脑系统
const CFStringRef kCGImagePropertyTIFFHostComputer;
//公司信息
const CFStringRef kCGImagePropertyTIFFCopyright;
//图片的白点
const CFStringRef kCGImagePropertyTIFFWhitePoint;
//图像的原色色度
const CFStringRef kCGImagePropertyTIFFPrimaryChromaticities;
//图片的瓦片宽度
const CFStringRef kCGImagePropertyTIFFTileWidth;
//图片的瓦片高度
const CFStringRef kCGImagePropertyTIFFTileLength;
kCGImagePropertyJFIFDictionary对应的字典中可能包含如下意义的键：
//JFIF版本
const CFStringRef kCGImagePropertyJFIFVersion;
//横向像素密度
const CFStringRef kCGImagePropertyJFIFXDensity;
//纵向像素密度
const CFStringRef kCGImagePropertyJFIFYDensity;
//像素密度单元
const CFStringRef kCGImagePropertyJFIFDensityUnit;
//是否是高质量图像版本
const CFStringRef kCGImagePropertyJFIFIsProgressive;
kCGImagePropertyExifDictionary对应的字典中可能包含如下意义的键 ：
//曝光时间
const CFStringRef kCGImagePropertyExifExposureTime;
//ExifNumber
const CFStringRef kCGImagePropertyExifFNumber;
//曝光程序
const CFStringRef kCGImagePropertyExifExposureProgram;
//每个通道的光谱灵敏度
const CFStringRef kCGImagePropertyExifSpectralSensitivity;
//ISO速度等级
const CFStringRef kCGImagePropertyExifISOSpeedRatings;
//ExifOECF
const CFStringRef kCGImagePropertyExifOECF;
//灵敏类型
const CFStringRef kCGImagePropertyExifSensitivityType;
//输出灵敏标准
const CFStringRef kCGImagePropertyExifStandardOutputSensitivity;
//推荐曝光指数
const CFStringRef kCGImagePropertyExifRecommendedExposureIndex;
//ISO速率
const CFStringRef kCGImagePropertyExifISOSpeed;
const CFStringRef kCGImagePropertyExifISOSpeedLatitudeyyy;
const CFStringRef kCGImagePropertyExifISOSpeedLatitudezzz;
//Exif版本
const CFStringRef kCGImagePropertyExifVersion;
//原始日期时间
const CFStringRef kCGImagePropertyExifDateTimeOriginal;
//数字化日期时间
const CFStringRef kCGImagePropertyExifDateTimeDigitized;
//压缩配置
const CFStringRef kCGImagePropertyExifComponentsConfiguration;
//压缩模式像素位
const CFStringRef kCGImagePropertyExifCompressedBitsPerPixel;
//快门速度值
const CFStringRef kCGImagePropertyExifShutterSpeedValue;
//孔径值
const CFStringRef kCGImagePropertyExifApertureValue;
//亮度值
const CFStringRef kCGImagePropertyExifBrightnessValue;
//曝光偏差值
const CFStringRef kCGImagePropertyExifExposureBiasValue;
//最大光圈值
const CFStringRef kCGImagePropertyExifMaxApertureValue;
//距离
const CFStringRef kCGImagePropertyExifSubjectDistance;
//测光模式
const CFStringRef kCGImagePropertyExifMeteringMode;
//光源
const CFStringRef kCGImagePropertyExifLightSource;
//拍摄时的闪光状态
const CFStringRef kCGImagePropertyExifFlash;
//焦距
const CFStringRef kCGImagePropertyExifFocalLength;
//主体区域
const CFStringRef kCGImagePropertyExifSubjectArea;
//相机制造商指定的信息
const CFStringRef kCGImagePropertyExifMakerNote;
//用户信息
const CFStringRef kCGImagePropertyExifUserComment;
//日期和时间标记的秒分数
const CFStringRef kCGImagePropertyExifSubsecTime;
//原始时间
const CFStringRef kCGImagePropertyExifSubsecTimeOriginal;
//数字时间
const CFStringRef kCGImagePropertyExifSubsecTimeDigitized;
//FlashPix版本信息
const CFStringRef kCGImagePropertyExifFlashPixVersion;
//色彩空间
const CFStringRef kCGImagePropertyExifColorSpace;
//X方向像素
const CFStringRef kCGImagePropertyExifPixelXDimension;
//Y方向像素
const CFStringRef kCGImagePropertyExifPixelYDimension;
//与图像相关的声音文件
const CFStringRef kCGImagePropertyExifRelatedSoundFile;
//FlashEnergy
const CFStringRef kCGImagePropertyExifFlashEnergy;
//FrequencyResponse
const CFStringRef kCGImagePropertyExifSpatialFrequencyResponse;
//像素数目
const CFStringRef kCGImagePropertyExifFocalPlaneXResolution;
const CFStringRef kCGImagePropertyExifFocalPlaneYResolution;
const CFStringRef kCGImagePropertyExifFocalPlaneResolutionUnit;
//图像主体的位置
const CFStringRef kCGImagePropertyExifSubjectLocation;
//选择的曝光指数
const CFStringRef kCGImagePropertyExifExposureIndex;
//传感器类型
const CFStringRef kCGImagePropertyExifSensingMethod;
//图像文件源
const CFStringRef kCGImagePropertyExifFileSource;
//场景类型
const CFStringRef kCGImagePropertyExifSceneType;
//CFA模块
const CFStringRef kCGImagePropertyExifCFAPattern;
//对图像数据进行特殊渲染
const CFStringRef kCGImagePropertyExifCustomRendered;
//曝光模式设置
const CFStringRef kCGImagePropertyExifExposureMode;
//白平衡模式
const CFStringRef kCGImagePropertyExifWhiteBalance;
//数字变焦比
const CFStringRef kCGImagePropertyExifDigitalZoomRatio;
//35毫米胶片的等效焦距
const CFStringRef kCGImagePropertyExifFocalLenIn35mmFilm;
//场景捕捉类型（标准，景观，肖像，夜晚）
const CFStringRef kCGImagePropertyExifSceneCaptureType;
//图像增益
const CFStringRef kCGImagePropertyExifGainControl;
//图像对比度
const CFStringRef kCGImagePropertyExifContrast;
//图像饱和度
const CFStringRef kCGImagePropertyExifSaturation;
//图像锐度
const CFStringRef kCGImagePropertyExifSharpness;
//拍摄条件
const CFStringRef kCGImagePropertyExifDeviceSettingDescription;
//主体距离
const CFStringRef kCGImagePropertyExifSubjectDistRange;
//图像的唯一标识
const CFStringRef kCGImagePropertyExifImageUniqueID;
//相机所有者
const CFStringRef kCGImagePropertyExifCameraOwnerName;
//相机序列号
const CFStringRef kCGImagePropertyExifBodySerialNumber;
//透镜规格信息
const CFStringRef kCGImagePropertyExifLensSpecification;
//透镜制造商名称
const CFStringRef kCGImagePropertyExifLensMake;
//透镜模式
const CFStringRef kCGImagePropertyExifLensModel;
//透镜序列号
const CFStringRef kCGImagePropertyExifLensSerialNumber;
//伽马设置
const CFStringRef kCGImagePropertyExifGamma;
