EXIF PropertyTagGpsLatitude 格式

Question

我正在以编程方式更新一堆扫描的 jpg 图像的 exif 数据

我更新大多数 exif 数据没有太大问题，但我很难设置 gps 坐标

例如我正在尝试按如下方式保存纬度坐标

PropertyItem PropertyTagGpsLatitude = srcImg.GetPropertyItem(2);
PropertyTagGpsLatitude.Value = System.Text.ASCIIEncoding.ASCII.GetBytes("42/1,5/1,33/1");
srcImg.SetPropertyItem(PropertyTagGpsLatitude);

根据其说明的文档

Latitude is expressed as three rational values giving the degrees, minutes, and seconds respectively. When degrees, minutes, and seconds are expressed, the format is dd/1, mm/1, ss/1. When degrees and minutes are used and, for example, fractions of minutes are given up to two decimal places, the format is dd/1, mmmm/100, 0/1.

https://msdn.microsoft.com/en-us/library/windows/desktop/ms534416(v=vs.85).aspx

我可以设置其他 gps 相关数据，例如这个转换正确

 PropertyItem PropertyTagGpsLatitudeRef = srcImg.GetPropertyItem(1);
 PropertyTagGpsLatitudeRef.Value = System.Text.ASCIIEncoding.ASCII.GetBytes("N");
 srcImg.SetPropertyItem(PropertyTagGpsLatitudeRef);

我没有遇到任何异常，我只是使用 Exif Pilot 实用程序验证 exif 数据，发现它无法正常工作

Answer 1

我终于想出了一个可行的解决方案。我加载了一张包含 GPS 信息的现有图像，以检查数据的结构。 Ultimatley 我能够在这里想出这个方法

 /// <summary>
 /// Prepares a byte array that hold EXIF latitude/longitude data
 /// </summary>
 /// <param name="degrees">There are 360° of longitude (180° E ↔ 180° W) and 180° of latitude (90° N ↔ 90° S)</param>
 /// <param name="minutes">Each degree can be broken into 60 minutes</param>
 /// <param name="seconds">Each minute can be divided into 60 seconds (”). For finer accuracy, fractions of seconds given by a decimal point are used. Seconds unit multiplied by 100. For example 33.77 seconds is passed as 3377. This gives adequate GPS precision</param>
 /// <returns></returns>
 private static byte[] FloatToExifGps(int degrees, int minutes, int seconds)
 {
      var secBytes = BitConverter.GetBytes(seconds);
      var secDivisor = BitConverter.GetBytes(100);
      byte[] rv = { (byte)degrees, 0, 0, 0, 1, 0, 0, 0, (byte)minutes, 0, 0, 0, 1, 0, 0, 0, secBytes[0], secBytes[1], 0, 0, secDivisor[0], 0, 0, 0 };
      return rv;
 }

然后像这样使用它

 PropertyItem PropertyTagGpsLongitude = srcImg.GetPropertyItem(4);
 PropertyTagGpsLongitude.Value = FloatToExifGps(79, 48, 3377);
 srcImg.SetPropertyItem(PropertyTagGpsLongitude);

我希望这对以后的人有所帮助

Answer 2

我最近遇到了同样的问题，想分享对我有用的解决方案。 LongitudeDegreeNumerator等变量都是uint类型，提前计算。

// Longitude: Build a whole property value
byte[] propertyTagGpsLongitude = new byte[24];
Buffer.BlockCopy(BitConverter.GetBytes(LongitudeDegreeNumerator), 0, propertyTagGpsLongitude, 0, 4);
Buffer.BlockCopy(BitConverter.GetBytes(LongitudeDegreeDenominator), 0, propertyTagGpsLongitude, 4, 4);
Buffer.BlockCopy(BitConverter.GetBytes(LongitudeMinuteNumerator), 0, propertyTagGpsLongitude, 8, 4);
Buffer.BlockCopy(BitConverter.GetBytes(LongitudeMinuteDenominator), 0, propertyTagGpsLongitude, 12, 4);
Buffer.BlockCopy(BitConverter.GetBytes(LongitudeSecondNumerator), 0, propertyTagGpsLongitude, 16, 4);
Buffer.BlockCopy(BitConverter.GetBytes(LongitudeSecondDenominator), 0, propertyTagGpsLongitude, 20, 4);

也许这对某人有用。

EXIF PropertyTagGpsLatitude 格式

EXIF PropertyTagGpsLatitude Format

c#

exif

image