转一篇文章，以便在后续文章中讲解——开源gis项目Mitab在C#中的使用方法

Yush

我一直是用MapX写的写MapInfo公司Tab格式的文件，但是由于涉及到大量的图元绘制，MapX的绘制速度是受到限制的，其绘制的速度并不快，于是探索是不是有比他更好的组件。前段时间曾经用过ShapeLib来绘制shp文件，其绘制的速度还是相当可以的，有兴趣的话可以搜搜，其提供的开源包中有实例程序，怎么来用。
而我今天要介绍的这个Mitab开源包中，并没有提供可以直接运行能看到效果的实例Demo，于是我开始了解如果在dot net程序中使用他。
Mitab开源项目是采用C++编写的库，其编译了mitab.dll文件，我们用他的功能也主要从这个dll中调用功能。但不是单纯的添加引用或者添加一个这个dll为控件能解决问题的，要用好这个dll，不得不继续分析他的开源包，在MiApi.cs文件中，有很多的[DllImport("mitab.dll")]语句，于是我明白了如何应用，下面来介绍他的应用步骤。
第一步：新建一个C#桌面应用程序；
第二步：添加开源库中的MiApi.cs和MiWrapper.cs两个类到程序中。
第三步：拷贝mitab.dll到程序的.exe的目录中，因为[DllImport("mitab.dll")]就是要查找系统运行的目录中是否存在这个dll文件，所以一定要拷贝。
第四步：写生成Tab文件的函数，调用MiApi.cs中函数。具体如何应用这些函数，请参考开源包中的mitab_vb_test.vb这个文件。
第五步：运行程序，生成Tab，搞定。
附我写的一个demo实例代码。

public void testWritefile()
{
WriteFile("D://11//testtab.tab", "tab");
}

private void WriteFile(string pszDest, string pszMifOrTab)
{
long dataset;

long feature;
double[] x = new double[100];
double[] y = new double[100];
long field_index;
string sTmp;
long i1;
long i2;

dataset = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_create(pszDest, pszMifOrTab, "CoordSys Earth Projection 1, 0", 90, 0, 180, -180);

if (dataset == 0)
{
sTmp = "";
sTmp = EBop.MapObjects.MapInfo.MiApi.mitab_c_getlasterrormsg();
MessageBox.Show("Failed to create " + pszMifOrTab + " file: " + sTmp);
return;
}

/* -------------------------------------------------------------------- */
/* Add a text, float and integer field. */
/* -------------------------------------------------------------------- */
field_index = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_add_field((System.IntPtr)dataset, "TestInt", 2, 8, 0, 0, 0);
field_index = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_add_field((System.IntPtr)dataset, "TestFloat", 5, 12, 2, 0, 0);
field_index = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_add_field((System.IntPtr)dataset, "TestString", 1, 10, 0, 0, 0);

/* -------------------------------------------------------------------- */
/* Write a point. */
/* -------------------------------------------------------------------- */
feature = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_create_feature((System.IntPtr)dataset, 1);

x[0] = 98;
y[0] = 50;

EBop.MapObjects.MapInfo.MiApi.mitab_c_set_points((System.IntPtr)feature, 0, 1, ref x[0], ref y[0]);
i1 = 256;
i2 = 255;
i1 = i1 * i2;
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_symbol((System.IntPtr)feature, 41, 15, (int)i1);
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_field((System.IntPtr)feature, 0, "100");
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_field((System.IntPtr)feature, 1, "100.5");
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_field((System.IntPtr)feature, 2, "12345678901234567890");
EBop.MapObjects.MapInfo.MiApi.mitab_c_write_feature((System.IntPtr)dataset, (System.IntPtr)feature);
EBop.MapObjects.MapInfo.MiApi.mitab_c_destroy_feature((System.IntPtr)feature);

/* -------------------------------------------------------------------- */
/* Write a MultiPoint. */
/* -------------------------------------------------------------------- */
feature = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_create_feature((System.IntPtr)dataset, 10);

x[0] = 90;
y[0] = 51;
x[1] = 90.5;
y[1] = 51.5;
x[2] = 91;
y[2] = 52;

EBop.MapObjects.MapInfo.MiApi.mitab_c_set_points((System.IntPtr)feature, 0, 3, ref x[0], ref y[0]);
i1 = 256;
i2 = 255;
i1 = i1 * i2;
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_symbol((System.IntPtr)feature, 41, 15, (int)i1);
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_field((System.IntPtr)feature, 0, "100");
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_field((System.IntPtr)feature, 1, "100.5");
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_field((System.IntPtr)feature, 2, "12345678901234567890");
EBop.MapObjects.MapInfo.MiApi.mitab_c_write_feature((System.IntPtr)dataset, (System.IntPtr)feature);
EBop.MapObjects.MapInfo.MiApi.mitab_c_destroy_feature((System.IntPtr)feature);

/* -------------------------------------------------------------------- */
/* Write a line. */
/* -------------------------------------------------------------------- */
feature = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_create_feature((System.IntPtr)dataset, 5);

x[0] = 100;
y[0] = 49;
x[1] = 101;
y[1] = 48;

EBop.MapObjects.MapInfo.MiApi.mitab_c_set_points((System.IntPtr)feature, 0, 2, ref x[0], ref y[0]);
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_pen((System.IntPtr)feature, 1, 2, 255);
EBop.MapObjects.MapInfo.MiApi.mitab_c_write_feature((System.IntPtr)dataset, (System.IntPtr)feature);
EBop.MapObjects.MapInfo.MiApi.mitab_c_destroy_feature((System.IntPtr)feature);

/* -------------------------------------------------------------------- */
/* Write text. */
/* -------------------------------------------------------------------- */
feature = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_create_feature((System.IntPtr)dataset, 4);

x[0] = 101;
y[0] = 51;

EBop.MapObjects.MapInfo.MiApi.mitab_c_set_points((System.IntPtr)feature, 0, 1, ref x[0], ref y[0]);
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_text((System.IntPtr)feature, "My text");
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_font((System.IntPtr)feature, "Arial");
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_text_display((System.IntPtr)feature, 45, 1, 7, 255 * 65536, 0, -1, -1, -1);
EBop.MapObjects.MapInfo.MiApi.mitab_c_write_feature((System.IntPtr)dataset, (System.IntPtr)feature);
EBop.MapObjects.MapInfo.MiApi.mitab_c_destroy_feature((System.IntPtr)feature);

/* -------------------------------------------------------------------- */
/* Write region (polygon). */
/* -------------------------------------------------------------------- */
feature = (long)EBop.MapObjects.MapInfo.MiApi.mitab_c_create_feature((System.IntPtr)dataset, 7);

x[0] = 101;
y[0] = 51;
x[1] = 100;
y[1] = 51;
x[2] = 100;
y[2] = 50;
x[3] = 101;
y[3] = 50;
x[4] = 101;
y[4] = 51;

EBop.MapObjects.MapInfo.MiApi.mitab_c_set_points((System.IntPtr)feature, 0, 5, ref x[0], ref y[0]);

x[0] = 100.5;
y[0] = 50.5;
x[1] = 100.5;
y[1] = 50.7;
x[2] = 100.7;
y[2] = 50.7;
x[3] = 100.7;
y[3] = 50.5;
x[4] = 100.5;
y[4] = 50.5;

EBop.MapObjects.MapInfo.MiApi.mitab_c_set_points((System.IntPtr)feature, 1, 5, ref x[0], ref y[0]);

EBop.MapObjects.MapInfo.MiApi.mitab_c_set_brush((System.IntPtr)feature, 255, 0, 2, 0);
EBop.MapObjects.MapInfo.MiApi.mitab_c_set_pen((System.IntPtr)feature, 1, 2, 65535);
EBop.MapObjects.MapInfo.MiApi.mitab_c_write_feature((System.IntPtr)dataset, (System.IntPtr)feature);
EBop.MapObjects.MapInfo.MiApi.mitab_c_destroy_feature((System.IntPtr)feature);
/* -------------------------------------------------------------------- */
/* Cleanup */
/* -------------------------------------------------------------------- */
EBop.MapObjects.MapInfo.MiApi.mitab_c_close((System.IntPtr)dataset);

if (EBop.MapObjects.MapInfo.MiApi.mitab_c_getlasterrorno() != 0)
{
sTmp = EBop.MapObjects.MapInfo.MiApi.mitab_c_getlasterrormsg();
//i1 = mitab_c_getlasterrormsg_vb(sTmp, 255);
MessageBox.Show("Last Error: " + sTmp);
}
}