上一篇介绍了Shape files文件结构，在这一篇，以面文件为例，写一下如何读取.shp文件，以面文件为例。
首先在ArcMap里面新建一个名为 三角形面 的 shp文件，用做测试数据。如下
测试数据下载地址为:http://download.csdn.net/detail/gis0911178/9650967
在Arcmap中显示如下
测试数据准备好之后，就可以在C#里面写代码来读取这个shp文件；代码如下
private void button1_Click(object sender, EventArgs e)
{
string shpfilepath = "";
OpenFileDialog openFileDialog1 = new OpenFileDialog();
openFileDialog1.Filter = "shapefile(*.shp)|*.shp|All files(*.*)|*.*"; //打开文件路径
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
shpfilepath = openFileDialog1.FileName;
BinaryReader br = new BinaryReader(openFileDialog1.OpenFile());
//读取文件过程
br.ReadBytes(24);
int FileLength = br.ReadInt32();
Console.WriteLine("文件长度:" + ChangeByteOrder(FileLength));
int FileBanben = br.ReadInt32();
ShapeType = br.ReadInt32();
xmin = br.ReadDouble();
ymin = br.ReadDouble();
xmax = br.ReadDouble();
ymax = br.ReadDouble();
Console.WriteLine("Xmin:" + xmin);
Console.WriteLine("Ymin:" + ymin);
Console.WriteLine("Xmax:" + xmax);
Console.WriteLine("Ymax:" + ymax);
double width = xmax - xmin;
double height = ymax - ymin;
n1 = (float)(this.panel1.Width * 0.9 / width);//x轴放大倍数
n2 = (float)(this.panel1.Height * 0.9 / height);//y轴放大倍数
br.ReadBytes(32);
switch (ShapeType)
{
case 1:
points.Clear();
while (br.PeekChar() != -1)
{
Point point = new Point();
uint RecordNum = br.ReadUInt32();
int DataLength = br.ReadInt32();
//读取第i个记录
br.ReadInt32();
point.X = br.ReadDouble();
point.Y = br.ReadDouble();
points.Add(point);
}
StreamWriter sw = new StreamWriter("point.txt");
foreach (Point p in points)
{
sw.WriteLine("{0},{1},{2}", p.X, -1 * p.Y, 0);
}
sw.Close();
break;
case 3:
polylines.Clear();
while (br.PeekChar() != -1)
{
Polyline polyline = new Polyline();
polyline.Box = new double[4];
polyline.Parts = new ArrayList();
polyline.Points = new ArrayList();
uint RecordNum = br.ReadUInt32();
int DataLength = br.ReadInt32();
//读取第i个记录
br.ReadInt32();
polyline.Box[0] = br.ReadDouble();
polyline.Box[1] = br.ReadDouble();
polyline.Box[2] = br.ReadDouble();
polyline.Box[3] = br.ReadDouble();
polyline.NumParts = br.ReadInt32();
polyline.NumPoints = br.ReadInt32();
for (int i = 0; i < polyline.NumParts; i++)
{
int parts = new int();
parts = br.ReadInt32();
polyline.Parts.Add(parts);
}
for (int j = 0; j < polyline.NumPoints; j++)
{
Point pointtemp = new Point();
pointtemp.X = br.ReadDouble();
pointtemp.Y = br.ReadDouble();
polyline.Points.Add(pointtemp);
}
polylines.Add(polyline);
}
StreamWriter sw2 = new StreamWriter("line.txt");
count = 1;
foreach (Polyline p in polylines)
{
for (int i = 0; i < p.NumParts; i++)
{
int startpoint;
int endpoint;
if (i == p.NumParts - 1)
{
startpoint = (int)p.Parts[i];
endpoint = p.NumPoints;
}
else
{
startpoint = (int)p.Parts[i];
endpoint = (int)p.Parts[i + 1];
}
sw2.WriteLine("线" + count.ToString() + ":");
for (int k = 0, j = startpoint; j < endpoint; j++, k++)
{
Point ps = (Point)p.Points[j];
sw2.WriteLine(" {0},{1},{2}", ps.X, ps.Y, 0);
}
count++;
}
}
sw2.Close();
break;
case 5:
polygons.Clear();
while(br.PeekChar()!=-1)
{
Polygon polygon = new Polygon();
polygon.Parts = new ArrayList();
polygon.Points = new ArrayList();
uint RecordNum = br.ReadUInt32();
//Console.Write("文件记录号为:"+RecordNum);
Console.WriteLine("文件记录号为:" + ChangeByteOrder((int)RecordNum));
int DataLength = br.ReadInt32();
//Console.Write("坐标长度为:"+DataLength);
Console.WriteLine("坐标长度为:" + ChangeByteOrder(DataLength));
//读取第i个记录
int m = br.ReadInt32();
Console.WriteLine("几何类型:"+m);
for (int i = 0; i < 4;i++ )
{
polygon.Box[i] = br.ReadDouble();
Console.WriteLine("Box[" + i + "]:" + polygon.Box[i]);
}
polygon.NumParts = br.ReadInt32();
Console.WriteLine("子面个数:"+polygon.NumParts);
polygon.NumPoints = br.ReadInt32();
Console.WriteLine("坐标点个数:" + polygon.NumPoints);
Console.WriteLine("每个子环在坐标点内的起始位置:");
for (int j = 0; j < polygon.NumParts;j++ )
{
int parts = new int();
parts = br.ReadInt32();
polygon.Parts.Add(parts);
Console.WriteLine("parts[" + j + "]:" + parts);
}
Console.WriteLine("Points数组:");
for (int j = 0; j < polygon.NumPoints;j++ )
{
Point pointtemp = new Point();
pointtemp.X = br.ReadDouble();
pointtemp.Y = br.ReadDouble();
polygon.Points.Add(pointtemp);
Console.WriteLine("Points["+j+"]:"+pointtemp.X+" "+pointtemp.Y);
}
polygons.Add(polygon);
Console.WriteLine("--------------------------");
}
break;
}
}
}
读取文件可以了解.shp文件的构成，这样才知道怎么去生成.shp文件。
为了清晰的看到结果，在这里我将每次读取到的东西都打印了出来，结果如下
--------------------------------------------------------------------------------
文件长度:110
Xmin:120.062485706624
Ymin:27.752624080108
Xmax:120.102341678472
Ymax:27.7716597681547
文件记录号为:1
坐标长度为:56
几何类型:5
Box[0]:120.062485706624
Box[1]:27.752624080108
Box[2]:120.102341678472
Box[3]:27.7716597681547
子面个数:1
坐标点个数:4
每个子环在坐标点内的起始位置:
parts[0]:0
Points数组:
Points[0]:120.062485706624 27.7618444915056
Points[1]:120.102341678472 27.7716597681547
Points[2]:120.081521394671 27.752624080108
Points[3]:120.062485706624 27.7618444915056
------------------------------------------------------------------------------------------------------
要注意.shp文件里面，文件长度、文件记录号、坐标长度 均为位序为big，读取跟写入的时候都要转换为little。位序转换函数如下：
private int ChangeByteOrder(int indata)
{
byte[] src = new byte[4];
src[0] = (byte)((indata >> 24) & 0xFF);
src[1] = (byte)((indata >> 16) & 0xFF);
src[2] = (byte)((indata >> 8) & 0xFF);
src[3] = (byte)(indata & 0xFF);
int value ;
value = (int)((src[0] & 0xFF) | ((src[1] & 0xFF) << 8) | ((src[2] & 0xFF) << 16) | ((src[3] & 0xFF) << 24));
return value;
}
代码里使用到的polygon.cs如下
class Polygon
{
public double[] Box=new double[4];
public int NumParts;
public int NumPoints;
public ArrayList Parts;
public ArrayList Points;
}