Linux C处理Arcmap导出的DEM栅格文件data.asc

关于栅格数据文件

读者可用自己的

作者在百度云网盘分享了一个

dataDEM.asc

http://pan.baidu.com/s/1o61C7W2

/**

 *【定义栅格数据文件头结构】

 */

struct GridFileHead{

int ncols;

int nrows;

double xllcorner;

double yllcorner;

double cellsize;

double NODATA_value;

};

struct GridFileHead GridHead;

/**

 *【读文件头】

 */

void readGridHead(char* lpFileName){

int hFile;

char szBuffer[256]={0};

int nBytesRead;

char* szTemp;

hFile = open(lpFileName,O_RDONLY);

nBytesRead = read(hFile,szBuffer,sizeof(szBuffer));

//ncols

szTemp = strstr(szBuffer,szncols);

GridHead.ncols = atoi(szTemp+strlen(szncols));

//nrows

szTemp = strstr(szBuffer,sznrows);

GridHead.nrows = atoi(szTemp+strlen(sznrows));

//xllcorner

szTemp = strstr(szBuffer,szxllcorner);

GridHead.xllcorner = atof(szTemp+strlen(szxllcorner));

//yllcorner

szTemp = strstr(szBuffer,szyllcorner);

GridHead.yllcorner = atof(szTemp+strlen(szyllcorner));

//cellsize

szTemp = strstr(szBuffer,szcellsize);

GridHead.cellsize = atof(szTemp+strlen(szcellsize));

//NODATA_value

szTemp = strstr(szBuffer,szNODATA_value);

GridHead.NODATA_value = atof(szTemp+strlen(szNODATA_value));

close(hFile);

}

/**

 *【读栅格数据】

 */

void readGridFileToDoubleArray2D(char* lpFileName){

int hFile;

char szBuffer[180]={0};

struct stat st;

char *lpFileMap,hFileMap;

char *lpOffset;

char *lpSplit;

char split=0x20;

double *gridInt=0;

hFile = open(lpFileName,O_RDONLY);

fstat(hFile,&st);

lpFileMap=mmap(NULL,st.st_size,PROT_READ,MAP_PRIVATE,hFile,0);

if(!index(lpFileMap,0x20)){

split=9;

}

lpOffset = strstr(lpFileMap,szNODATA_value);

lpOffset = index(lpOffset,0x0A);

lpOffset++;

int i,j;

for(i=0; i<GridHead.nrows; i++){

for(j=0;j<GridHead.ncols-1;j++){

arrDouble2D[i][j]=atof(lpOffset);

lpSplit=index(lpOffset,split);

lpOffset=lpSplit+1;

}

arrDouble2D[i][GridHead.ncols-1]=atof(lpOffset);

lpSplit=index(lpOffset,0x0A);

lpOffset++;

}

munmap(lpFileMap,st.st_size);

close(hFile);

}

/**

 *【写二维数组到文件】

 */

void writeDoubleArray2DtoGridFile(char* lpFileName, double **arrDouble2D){

char szFileName[255]={0};

char szBuffer[81920]={0};

char szTmp[64]={0};

memset(szFileName,0,sizeof(szFileName));

strcat(szFileName,”_out.asc”);

int hOut;

hOut = open(szFileName,O_RDWR|O_CREAT);

vsprf(szBuffer,”ncols %d\r\nnrows %d\r\nxllcorner %f\r\nyllcorner %f\r\ncellsize %f\r\nNODATA_value %f\r\n”,

GridHead.ncols,

GridHead.nrows,

GridHead.xllcorner,

GridHead.yllcorner,

GridHead.cellsize,

GridHead.NODATA_value

);

write(hOut,szBuffer,strlen(szBuffer));

memset(szBuffer,0,sizeof(szBuffer));

int i,j;

for(i=0;i<GridHead.nrows;i++){

for(j=0;j<GridHead.ncols;j++){

memset(szTmp,0,sizeof(szTmp));

vsprf(szTmp,”%f “,arrDouble2D[i][j]);

strcat(szBuffer,szTmp);

}

strcat(szBuffer,”\r\n”);

write(hOut,szBuffer,strlen(szBuffer));

memset(szBuffer,0,sizeof(szBuffer));

}

close(hOut);

}

/**

 *【格式化输出的子程序】

 *【在上面第5步中用到】

 */

int vsprf(char *str,char *format,…){

va_list ap;

int count;

va_start(ap,format);

count=vsprintf(str,format,ap);

va_end(ap);

return count;

}

【编写主程序】

#include <stdio.h>

#include <stdlib.h>

#include <stdarg.h>

#include <fcntl.h>

#include <unistd.h>

#include <string.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/mman.h>

#include <math.h>

/**

 *

 */

struct GridFileHead{

int ncols;

int nrows;

double xllcorner;

double yllcorner;

double cellsize;

double NODATA_value;

};

struct GridFileHead GridHead;

/**

 *

 */

char *szncols = “ncols”;

char *sznrows = “nrows”;

char *szxllcorner = “xllcorner”;

char *szyllcorner = “yllcorner”;

char *szcellsize = “cellsize”;

char *szNODATA_value = “NODATA_value”;

double **arrDouble2D=0;

/**

 *

 */

void main(int argc, char *argv[]) {

/**

*read grid file head

*/

char *strFileInput=argv[1];

readGridHead(strFileInput);

/**

*allocate memory for array

*/

arrDouble2D=(int **)calloc(GridHead.nrows,sizeof(double *));

int i;

for(i=0;i<GridHead.nrows;i++){

*(arrDouble2D+i)=(int *)calloc(GridHead.ncols, sizeof(double));

}

readGridFileToDoubleArray2D(strFileInput);

/**

*

*/

writeDoubleArray2DtoGridFile(“dataout.asc”,arrDouble2D);

/**

*free memory

*/

for(i=0;i<GridHead.nrows;i++){

free(*(arrDouble2D+i));

}

free(arrDouble2D);

}

【测试运行，结果如下】