如何读取GeoTIFF文件从C＃ [英] How to read GeoTIFF file from C#

问题描述

我已经获得了一些地区的数字高程地图（地球的高度图）。我的目标是创建现实地形。

地形生成没有问题。我实践了使用VC＃& XNA框架。

问题是那些高度地图文件是GeoTIFF格式，我不知道如何阅读。我也没有以前的经验，阅读任何图像文件，以便我可以使用一些小秘诀，在互联网上提供的关于读取GeoTIFF文件的实验。

• geoTIFF文件是3601 x 3601个文件。


• 每个文件有两个版本，一个十进制&


• 每个文件都有每秒钟经度和数据的数据。纬度
  Geo-Coords以及高度图，即Lon，Lat，海拔高度

如何阅读这些文件：）

我有来自ASTER G-DEM版本2的文件链接到官方说明根据他们GeoTIFF是非常标准，这是因为一些GeoTIFF可视化我下载显示正确的数据。

我要使用C＃。

---

EDIT

好吧，我得到了 libtiff ，这是我做的，

  using（Tiff tiff = Tiff.Open（@Test\N41E071_dem.tif，r））
 {
 int width = tiff.GetField（TiffTag.IMAGEWIDTH）[0] .ToInt（）; 
 int height = tiff.GetField（TiffTag.IMAGELENGTH）[0] .ToInt（）; 
 double dpiX = tiff.GetField（TiffTag.XRESOLUTION）[0] .ToDouble ; 
 double dpiY = tiff.GetField（TiffTag.YRESOLUTION）[0] .ToDouble（）; 
 
 byte [] scanline = new byte [tiff.ScanlineSize（）]; 
 ushort [] scanline16Bit = new ushort [tiff.ScanlineSize（）/ 2]; 
 
 for（int i = 0; i  {
 tiff .ReadScanline（scanline，i）; //加载第i行
 MultiplyScanLineAs16BitSamples（scanline，scanline16Bit，16，i）; 
} 
} 
 
 private static void MultiplyScanLineAs16BitSamples （byte [] scanline，ushort [] temp，ushort factor，int row）
 {
 if（scanline.Length％2！= 0）
 {
 // each two字节定义一个样本，所以应该有偶数个字节
 throw new ArgumentException（）; 
} 
 
 Buffer.BlockCopy（scanline，0，temp，0，scanline.Length）; 
 
 for（int i = 0; i  {
 temp [i] * = factor; 
 MessageBox.Show（Row：+ row.ToString（）+Column：+（i / 2）.ToString（）+Value：+ temp [i] .ToString（））; 
} 
} 
  

在显示消息框时，相应的值，我做的正确，我问这个铜像这是我的第一个图像的经验& 8 \16位问题。我认为不同于官方教程libtiff我应该使用短而不是 ushort ，因为我使用的图像是GeoTIFF，有符号的16位

解决方案

有一些SDK可以从C＃读取GeoTIFF文件：

• http://www.bluemarblegeo.com/ global-mapper / developer / developer.php＃details （commercial）


• http：// bitmiracle.com/libtiff/ （免费）


• http：//

$ b

GeoTIFF的规范可以这里 - 对我来说似乎GeoTIFF可以包含不同的子类型信息，而这些信息又需要进行相应的解释...




I have acquired Digital Elevation Maps(Height Map of Earth) of some area. My aim was to create Realistic Terrains.

Terrain Generation is no problem. I have practiced that using VC# & XNA framework.

The problem is that those Height Map Files are in GeoTIFF format which i don't know how to read. Nor do i have previous experience with reading any image files so that i could experiment something using little tips-bits available on internet about reading GeoTIFF files. So far i have been unsuccessful.

• The geoTIFF files I have are 3601 x 3601 files.
• Each file has two version, a decimal & num valued files.
• Each file has data of every second of longitude & latitude of Geo-Coords along with Height Map i.e Lon, Lat, height from sea level

How to read these file :)

The files I have are from ASTER G-DEM Version-2 LINK TO OFFICIAL DESCRIPTION according to them GeoTIFF is pretty standard which is because some GeoTIFF Visualizers I dwonloaded are showing me the correct data.

I am gonna be using C#. I would appreciate if we talk in relation to this language.

---

E D I T

okay i got the libtiff and this what i have done,

using (Tiff tiff = Tiff.Open(@"Test\N41E071_dem.tif", r"))
{
  int width   = tiff.GetField(TiffTag.IMAGEWIDTH)[0].ToInt();
  int height  = tiff.GetField(TiffTag.IMAGELENGTH)[0].ToInt();
  double dpiX = tiff.GetField(TiffTag.XRESOLUTION)[0].ToDouble();
  double dpiY = tiff.GetField(TiffTag.YRESOLUTION)[0].ToDouble(); 

  byte[] scanline        = new byte[tiff.ScanlineSize()]; 
  ushort[] scanline16Bit = new ushort[tiff.ScanlineSize() / 2];

  for (int i = 0; i < height; i++)
  {
    tiff.ReadScanline(scanline, i); //Loading ith Line                        
    MultiplyScanLineAs16BitSamples(scanline, scanline16Bit, 16,i);
  }
}

private static void MultiplyScanLineAs16BitSamples(byte[] scanline, ushort[] temp, ushort factor,int row)
{
  if (scanline.Length % 2 != 0)
  {
    // each two bytes define one sample so there should be even number of bytes
    throw new ArgumentException();
  }

  Buffer.BlockCopy(scanline, 0,   temp, 0, scanline.Length);

  for (int i = 0; i < temp.Length; i++)
  {                
    temp[i] *= factor;
    MessageBox.Show("Row:"+row.ToString()+"Column:"+(i/2).ToString()+"Value:"+temp[i].ToString());
  }
}

where i am displaying the message box, i am displaying the corresponding values, Am i doing it Right, i am asking this cuz this is my maiden experience with images & 8\16 bit problem. I think unlike the official tutorials of libtiff i should be using short instead of ushort because the images i am using are "GeoTIFF, signed 16 bits"

解决方案

There are some SDKs out there usable from C# to read GeoTIFF files:

• http://www.bluemarblegeo.com/global-mapper/developer/developer.php#details (commercial)
• http://bitmiracle.com/libtiff/ (free)
• http://trac.osgeo.org/gdal/wiki/GdalOgrInCsharp (free?)

UPDATE:

The spec for GeoTIFF can befounf here - to me it seems that GeoTIFFs can contain different "subtypes" of information which in turn need to be interpreted appropriately...

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