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  • .net c#通过Exif获取图片信息(参数)

    简介

          想要获取图片的信息,例如快门速度、ISO值等等,我们可以通过读取Exif中存储的信息。Exif(Exchangeable Image File)是存储在JPEG格式照片头部的一段信息,相机和手机拍摄的照片都会携带这些信息,但是需要注意,PS的照片的时候采用低质量保存会丢失这些信息。在PS中保存为10-12等级的时候不会丢失,在美图秀秀中保存质量为100%不会丢失。软件在处理的时候也会将自己的信息写入Exif,所以也可以通过这种方式判断是否为原图,或者图片是否经过处理。

         本文中我介绍两种方式获取Exif。一是C#自带的Image.PropertyItems 属性(了解),二是通过第三方控件metadata-extractor获取(推荐)。

    一、通过Image.PropertyItems 属性获取照片信息

    Image.PropertyItems 属性中有几个重要属性,Id:为int型,不同的Id表示不同的参数的;Value:表示参数的值,byte[]型;Len:为int型,表示Value的长度,以字节为单位;Type:short型,表示Value的取数方法。Type主要有以下几个类型:

    type=1 时 Value 为字节数组。

    type=2 时 Value 为空终止 ASCII 字符串。如果将类型数据成员设置为 ASCII 类型,则应该将 Len 属性设置为包括空终止的字符串长度。例如,字符串“Hello”的长度为 6

    type=3 时 Value 为无符号的短(16 位)整型数组。

    type=4 时 Value 为无符号的长(32 位)整型数组。

    type=5 时 Value 数据成员为无符号的长整型对数组。每一对都表示一个分数;第一个整数是分子,第二个整数是分母。

    type=6 时 Value 为可以包含任何数据类型的值的字节数组。

    type=7 时 Value 为有符号的长(32 位)整型数组。

    type=10 时 Value 为有符号的长整型对数组。每一对都表示一个分数;第一个整数是分子,第二个整数是分母。

    参考文献:http://blog.csdn.net/yang073402/article/details/5470127

    在使用Image.PropertyItems属性时需要引用:using System.Drawing

     下面是代码:

    #region 通过PropertyItems获取照片参数
    
            /// <summary>
            /// 表示参数的结构
            /// </summary>
            public struct Exif 
            {
                /// <summary>
                /// 数据的ID
                /// </summary>
                public string Id;
                /// <summary>
                /// 数据类型
                /// </summary>
                public int Type;
                /// <summary>
                /// 数据中值的字节长度
                /// </summary>
                public int Length;
    
                /// <summary>
                /// 根据ID对应的中文名
                /// </summary>
                public string Name;
    
                /// <summary>
                /// 根据原字节解析的参数值
                /// </summary>
                public string Value;
            }
    
            /// <summary>将字节通过ASCII转换为字符串
            /// </summary>
            /// <param name="bt">原字节</param>
            /// <returns></returns>
            private static string ToStrOfByte(this byte[] bt)
            {
                return Encoding.ASCII.GetString(bt);
            }
    
            /// <summary>将字节转换为int
            /// </summary>
            /// <param name="bt">原字节</param>
            /// <returns></returns>
            private static int ToUnInt16(this byte[] bt)
            {
                return Convert.ToUInt16(bt[1] << 8 | bt[0]);
            }
    
            /// <summary>将原两组字节转换为uint
            /// </summary>
            /// <param name="bt">原字节</param>
            /// <param name="isFirst">是否转第一个字节组</param>
            /// <returns></returns>
            private static uint ToUnInt32(this byte[] bt,bool isFirst=true)
            {
                return isFirst ? Convert.ToUInt32(bt[3] << 24 | bt[2] << 16 | bt[1] << 8 | bt[0]) : Convert.ToUInt32(bt[7] << 24 | bt[6] << 16 | bt[5] << 8 | bt[4]);
            }
    
            /// <summary>获取曝光模式
            /// </summary>
            /// <param name="value">曝光模式值</param>
            /// <returns></returns>
            private static string ExposureMode(int value)
            {
                var rt = "Undefined";
                switch (value)
                {
                    case 0:
                        rt = "自动"; break;
                    case 1:
                        rt = "手动控制"; break;
                    case 2:
                        rt = "程序控制"; break;
                    case 3:
                        rt = "光圈优先"; break;
                    case 4:
                        rt = "快门优先"; break;
                    case 5:
                        rt = "夜景模式"; break;
                    case 6:
                        rt = "运动模式"; break;
                    case 7:
                        rt = "肖像模式"; break;
                    case 8:
                        rt = "风景模式"; break;
                    case 9:
                        rt = "其他模式"; break;
                }
                return rt;
            }
    
            /// <summary>获取测光模式
            /// </summary>
            /// <param name="value">测光模式值</param>
            /// <returns></returns>
            private static string MeteringMode(int value)
            {
                var rt = "Unknown";
                switch (value)
                {
                    case 0:
                        rt = "Unknown"; break;
                    case 1:
                        rt = "平均测光"; break;
                    case 2:
                        rt = "中央重点平均测光"; break;
                    case 3:
                        rt = "点测光"; break;
                    case 4:
                        rt = "多点测光"; break;
                    case 5:
                        rt = "评价测光"; break;
                    case 6:
                        rt = "局部测光"; break;
                    case 255:
                        rt = "其他测光"; break;
                }
                return rt;
            }
    
            /// <summary>获取闪光灯模式
            /// </summary>
            /// <param name="value">闪光灯值</param>
            /// <returns></returns>
            private static string FlashMode(int value)
            {
                var rt = "Unkown";
                switch (value)
                {
                    case 0:
                        rt = "未使用"; break;
                    case 1:
                        rt = "使用闪光灯"; break;
                }
                return rt;
            }
    
            /// <summary>获取白平衡模式
            /// </summary>
            /// <param name="value">白平衡值</param>
            /// <returns></returns>
            private static string WhiteBalance(int value)
            {
                var rt = "Unkown";
                switch (value)
                {
                    case 0: rt = "自动";//Unkown
                        break;
                    case 1: rt = "日光";
                        break;
                    case 2: rt = "荧光灯";
                        break;
                    case 3: rt = "白炽灯";
                        break;
                    case 17: rt = "标准光源A";
                        break;
                    case 18: rt = "标准光源B";
                        break;
                    case 19: rt = "标准光源C";
                        break;
                    case 255: rt = "其他";
                        break;
                }
                return rt;
            }
    
            /// <summary>通过Id获取Exif中关键名称和值
            /// </summary>
            /// <param name="pId">ID</param>
            /// <param name="pType">类型</param>
            /// <param name="pBytes">字节值</param>
            /// <returns></returns>
            private static Exif InfoOfExif(int pId,int pType,byte[] pBytes)
            {
    
                var rt=new Exif {
                    Id ="0X"+pId.ToString("X"), 
                    Length = pBytes.Length, 
                    Type = pType
                };
                uint fm;
                uint fz;
                switch (pId)
                {
                    case 0x010F:
                        rt.Name = "相机制造商";
                        rt.Value = pBytes.ToStrOfByte();
                        break;
                    case 0x0110:
                        rt.Name = "相机型号";
                        rt.Value = pBytes.ToStrOfByte();
                        break;
                    case 0xA433:
                        rt.Name = "镜头制造商";
                        rt.Value = pBytes.ToStrOfByte();
                        break;
                    case 0xA434:
                        rt.Name = "镜头型号";
                        rt.Value = pBytes.ToStrOfByte();
                        break;
                    case 0x9003:
                        rt.Name = "拍摄时间";
                        var temp=pBytes.ToStrOfByte().Split(' ');
                        rt.Value =temp[0].Replace(":","/")+" "+temp[1];
                        break;
                    case 0x0132:
                        rt.Name = "修改时间";
                        temp=pBytes.ToStrOfByte().Split(' ');
                        rt.Value =temp[0].Replace(":","/")+" "+temp[1];
                        break;
                    case 0x0131:
                        rt.Name = "软件";
                        rt.Value = pBytes.ToStrOfByte();
                        break;
                    case 0xA002:
                        rt.Name = "图像高度";
                        rt.Value = pBytes.ToUnInt16()+" px";
                        break;
                    case 0xA003:
                        rt.Name = "图像宽度";
                        rt.Value = pBytes.ToUnInt16()+" px";
                        break;
                    case 0x011A:
                         fm=pBytes.ToUnInt32(false); 
                         fz= pBytes.ToUnInt32();
                        rt.Value = fm == 1 ? fz.ToString() : fz + "/" + fm;
                        rt.Value+=" dpi";
                        rt.Name = "水平方向分辨率";
                        break;
                    case 0x011B:
                        fm=pBytes.ToUnInt32(false); 
                         fz= pBytes.ToUnInt32();
                        rt.Value = fm == 1 ? fz.ToString() : fz + "/" + fm;
                        rt.Value += " dpi";
                        rt.Name = "垂直方向分辨率";
                        break;
                    case 0x8822:
                        rt.Value = ExposureMode(pBytes.ToUnInt16());
                        rt.Name = "曝光程序";
                        break;
                    case 0x9207:
                        rt.Value = MeteringMode(pBytes.ToUnInt16());
                        rt.Name = "测光模式";
                        break;
                    case 0x829A:
                        fm=pBytes.ToUnInt32(false); 
                        fz= pBytes.ToUnInt32();
                        //分母大于分子写为1/XXX,分母小于分子,写为保留一位小数
                        rt.Value = fm>fz ? "1/"+fm/fz:((double)fz/fm).ToString("0.0");
                        rt.Value += "";
                        rt.Name = "曝光时间";
                        break;
                    case 0x8827:
                        rt.Value = pBytes.ToUnInt16().ToString();
                        rt.Name = "ISO";
                        break;
                    case 0x920A:
                        fm=pBytes.ToUnInt32(false); 
                         fz= pBytes.ToUnInt32();
                        rt.Value=fm==1?fz.ToString():((double)fz/fm).ToString("0.00");
                        rt.Value += " mm";
                        rt.Name = "焦距";
                        break;
                    case 0x829D:
                        rt.Value ="f/"+((double)pBytes.ToUnInt32() / pBytes.ToUnInt32(false));
                        rt.Name = "光圈";
                        break;
                    
                    case 0x9204:
                        fm = pBytes.ToUnInt32(false);
                        var fz1=Convert.ToInt32(pBytes[3] << 24 | pBytes[2] << 16 | pBytes[1] << 8 | pBytes[0]);
                        //曝光补偿要加+ -
                        rt.Value = fz1 > 0 ? "+" : "";
                        rt.Value +=fz1 == 0 ? "0" : fz1+ "/"+ fm;
                        rt.Name = "曝光补偿";
                        break;
                    case 0x9208:
                        rt.Value = WhiteBalance(pBytes.ToUnInt16());
                        rt.Name = "白平衡";
                        break;
                    case 0x9209:
                        rt.Value = FlashMode(pBytes.ToUnInt16());
                        rt.Name = "闪光灯";
                        break;
                    default: rt.Name = "其他";
                        rt.Value = "Unkown";
                        break;
                }
                return rt;
            }
    
            /// <summary>通过PropertyItems获取照片参数
            /// </summary>
            /// <param name="imgPath">照片的绝对路径</param>
            /// <returns>参数的集合</returns>
            public static IEnumerable<Exif> GetExifByPi(string imgPath)
            {
                var img = Image.FromFile(imgPath);
                var pItems = img.PropertyItems;//将"其他"信息过滤掉
                return pItems.Select(pi => InfoOfExif(pi.Id, pi.Type, pi.Value)).Where(j=>j.Name!="其他").ToList();
            }
    
            #endregion

    在调用的时候用 var piList=GetExifByPi("照片路径");这种方法需要注意以下几个方面:

    注意:

    1、Image.PropertyItems的Type中同一个类型有的时候不能用同一个方法得到,这是由于参数的表现方式不同,所以建议用Id,每一个ID用对应的方法将byte[]装换为string。

    2、不同型号的手机和相机Exif中存储方式不一样,这一点非常重要,也就是说这个方法其实无法准确获每个图片的信息。我们需要将每种相机和手机分别用不同方法获取,这个工作量太大了,幸好有第三方插件。

    二、通过metadata-extractor获取照片参数

    metadata-extractor是目前最简单易用的EXIF信息处理包,是由Drew Noakes写的。官网: https://drewnoakes.com/code/exif/  官网上面的是用的.nupkg的文件,而不是传统的.dll文件,需要通过nuget引入本地。如果不会安装和使用nuget的可以参考文献:http://www.cnblogs.com/chsword/archive/2011/09/14/NuGet_Install_OperatePackage.html  成功安装nuget后再vs中点击:工具->NuGet程序包管理器->程序包管理器控制台。

    然后在"pm>"处输入:Install-Package MetadataExtractor  可以参考:https://www.nuget.org/packages/MetadataExtractor/ 

    最后将dll引用到您的项目中:

    完整代码:

    #region 通过metadata-extractor获取照片参数
    
            //参考文献
            //官网: https://drewnoakes.com/code/exif/
            //nuget 官网:https://www.nuget.org/
            //nuget 使用: http://www.cnblogs.com/chsword/archive/2011/09/14/NuGet_Install_OperatePackage.html
            //nuget MetadataExtractor: https://www.nuget.org/packages/MetadataExtractor/
    
            /// <summary>通过MetadataExtractor获取照片参数
            /// </summary>
            /// <param name="imgPath">照片绝对路径</param>
            /// <returns></returns>
            public static Dictionary<string,string> GetExifByMe(string imgPath)
            { 
                var rmd = ImageMetadataReader.ReadMetadata(imgPath);
                var rt=new Dictionary<string,string>();
                foreach (var rd in rmd)
                {
                    foreach(var tag in rd.Tags)
                    {
                        var temp = EngToChs(tag.Name);
                        if (temp == "其他")
                        {
                            continue;
                        }
                        if (!rt.ContainsKey(temp))
                        {
                            rt.Add(temp, tag.Description);
                        }
                        
                    }
                }
                return rt;
            }
    
            /// <summary>筛选参数并将其名称转换为中文
            /// </summary>
            /// <param name="str">参数名称</param>
            /// <returns>参数中文名</returns>
            private static string EngToChs(string str)
            {
                var rt = "其他";
                switch (str)
                {
                    case "Exif Version": rt = "Exif版本";
                        break;
                    case "Model": rt = "相机型号";
                        break;
                    case "Lens Model": rt = "镜头类型";
                        break;
                    case "File Name": rt = "文件名";
                        break;
                    case "File Size": rt = "文件大小";
                        break;
                    case "Date/Time": rt = "拍摄时间";
                        break;
                    case "File Modified Date": rt = "修改时间";
                        break;
                    case "Image Height": rt = "照片高度";
                        break;
                    case "Image Width": rt = "照片宽度";
                        break;
                    case "X Resolution": rt = "水平分辨率";
                        break;
                    case "Y Resolution": rt = "垂直分辨率";
                        break;
                    case "Color Space": rt = "色彩空间";
                        break;
    
                    case "Shutter Speed Value": rt = "快门速度";
                        break;
                    case "F-Number": rt = "光圈";//Aperture Value也表示光圈
                        break;
                    case "ISO Speed Ratings": rt = "ISO";
                        break;
                    case "Exposure Bias Value": rt = "曝光补偿";
                        break;
                    case "Focal Length": rt = "焦距";
                        break;
    
                    case "Exposure Program": rt = "曝光程序";
                        break;
                    case "Metering Mode": rt = "测光模式";
                        break;
                    case "Flash Mode": rt = "闪光灯";
                        break;
                    case "White Balance Mode": rt = "白平衡";
                        break;
                    case "Exposure Mode": rt = "曝光模式";
                        break;
                    case "Continuous Drive Mode": rt = "驱动模式";
                        break;
                    case "Focus Mode": rt = "对焦模式";
                        break;
                }
                return rt;
            }
    
            #endregion

    使用的时候:var me=GetExifByMe(); 

    注意:

    1、var rmd = ImageMetadataReader.ReadMetadata(imgPath);方法里可以是照片路径和Stream类型。

    2、metadata-extractor会将所有信息读出来,而且还是英文的,所以要将里面的数据进行选取,需要的还要转换为中文。

    参考文献:
    官网: https://drewnoakes.com/code/exif/
    nuget MetadataExtractor: https://www.nuget.org/packages/MetadataExtractor/
    nuget 使用: http://www.cnblogs.com/chsword/archive/2011/09/14/NuGet_Install_OperatePackage.html

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  • 原文地址:https://www.cnblogs.com/fancyblogs/p/5639960.html
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