如何使用C编程创建图像数据库？

Question

我需要使用C编程创建一个简单的数据库来存储图像。然后，我如何使用数据库将图像一个接一个地传送到另一个应用程序。每张图片都有一个ID。如果任何图像与我的应用程序需要匹配。其相应的ID必须打印为输出。

我需要为大约350个图像创建数据库。我的主应用程序已经用C编写了。那么，任何人都可以帮助我如何创建数据库以及如何将它与主应用程序链接起来？

Answer 1

最简单的方法是将BLOB存储在sqlite db中，该db作为单个.c文件集成到您的项目中。请参阅示例C文件，其中演示了访问blob的两种不同方式。一个使用绑定和一个使用blob api。

#include <stdio.h> 
#include <ctype.h> 
#include <string.h> 
#include <stdlib.h> 
#include <limits.h> 
#include <sys/time.h> 
#include <unistd.h> 
#include <libgen.h> 
#include "sqlite3.h" 

sqlite3 *db; 

int error(char *msg) { 
    fprintf(stderr, "ERROR: %s\n", msg); 
    if(db) 
     sqlite3_close(db); 
    exit(1); 
} 

int gettype(char **imgtype, int columns, char **colval, char **colname) { 
    int col; 

    if(columns!=1) 
     return 1; 

    snprintf((char *)imgtype, 4, "%s", colval[0]); 

    return 0; 
} 

int getrowid(sqlite3_int64 *rowid, int columns, char **colval, char **colname) { 
    int col; 

    if(columns!=1) 
     return 1; 

    *rowid=(int)strtol(colval[0], NULL, 10); 

    return 0; 
} 

int main(int argc, char **argv) { 
    enum { PROG, FUNC, TABLE, NAME }; 

    sqlite3_blob *dblob; 
    char sqlcmd[1024]; 
    sqlite3_int64 rowid=0; 
    sqlite3_stmt *stmt; 
    char *zErrMsg=0; 

    char filename[1024]; 
    char outname[1024]; 
    char imgtype[4]; 
    FILE *fblob; 
    char *blobmem; 
    long blobsize; 


    if(argc!=4) 
     error("usage: blob <get|put> <table> <filename>"); 


    if(sqlite3_open(DATABASE, &db)) 
     error((char*)sqlite3_errmsg(db)); 

    sqlite3_busy_timeout(db, TIMEOUT); 


    // using bind api 
    if(strcmp(argv[FUNC], "put")==0) { 
     snprintf(filename, 1024, "%s", basename(argv[NAME])); 
     strtok(filename, "."); 
     snprintf(imgtype, 4, "%s", strtok(NULL, ".")); 

     if(!strlen(imgtype) || !(strcasecmp(imgtype, "gif")==0 || strcasecmp(imgtype, "jpg")==0 || strcasecmp(imgtype, "png")==0)) 
      error("wrong extension/img type"); 

     fblob=fopen(argv[NAME], "r"); 
     if(fblob==NULL) 
      error("file not found"); 

     fseek(fblob, 0L, SEEK_END); 
     blobsize=ftell(fblob); 
     if(!blobsize) 
      error("wrong file size"); 

     blobmem=malloc(blobsize); 
     if(!blobmem) 
      error("unable to allocate memory"); 

     rewind(fblob); 
     if(fread(blobmem, blobsize, 1, fblob)!=1) 
      error("unable to read file"); 
     fclose(fblob); 

     snprintf(sqlcmd, 1024, "delete from '%s' where name like '%s';", argv[TABLE], filename); 
     if(sqlite3_exec(db, sqlcmd, NULL, NULL, &zErrMsg)!=SQLITE_OK) 
      error(zErrMsg); 

     snprintf(sqlcmd, 1024, "insert into '%s'(name, type, data) values(?, ?, ?);", argv[TABLE]); 
     if(sqlite3_prepare_v2(db, sqlcmd, -1, &stmt, 0)!=SQLITE_OK) 
      error((char*)sqlite3_errmsg(db)); 

     sqlite3_bind_text(stmt, 1, filename, -1, SQLITE_STATIC); 
     sqlite3_bind_text(stmt, 2, imgtype, -1, SQLITE_STATIC); 
     sqlite3_bind_blob(stmt, 3, blobmem, blobsize, SQLITE_STATIC); 

     if(sqlite3_step(stmt)!=SQLITE_DONE) 
      error((char*)sqlite3_errmsg(db)); 

     if(sqlite3_finalize(stmt)!=SQLITE_OK) 
      error((char*)sqlite3_errmsg(db)); 

     free(blobmem); 

    } 
    // using blob api 
    else if(strcmp(argv[FUNC], "get")==0) { 
     snprintf(filename, 1024, "%s", argv[NAME]); 
     strtok(filename, "."); 

     snprintf(sqlcmd, 1024, "select rowid from '%s' where name like '%s';", argv[TABLE], filename); 
     if(sqlite3_exec(db, sqlcmd, (void *)&getrowid, &rowid, &zErrMsg)!=SQLITE_OK) 
      error(zErrMsg); 

     if(!rowid) 
      error("not found"); 

     snprintf(sqlcmd, 1024, "select type from '%s' where name like '%s';", argv[TABLE], filename); 
     if(sqlite3_exec(db, sqlcmd, (void *)&gettype, &imgtype, &zErrMsg)!=SQLITE_OK) 
      error(zErrMsg); 

     if(!strlen(imgtype) || !(strcasecmp(imgtype, "gif")==0 || strcasecmp(imgtype, "jpg")==0 || strcasecmp(imgtype, "png")==0)) 
      error("wrong extension/img type"); 

     if(sqlite3_blob_open(db, "main", argv[TABLE], "data", rowid, 0, &dblob)!=SQLITE_OK) 
      error((char*)sqlite3_errmsg(db)); 

     blobsize=sqlite3_blob_bytes(dblob); 
     if(!blobsize) 
      error("image is 0 bytes in size"); 

     blobmem=malloc(blobsize); 
     if(!blobmem) 
      error("unable to allocate memory"); 

     if(sqlite3_blob_read(dblob, blobmem, blobsize, 0)!=SQLITE_OK) 
      error("unable to read image"); 

     sqlite3_blob_close(dblob); 

     snprintf(outname, 1024, "%s.%s", filename, imgtype); 
     fblob=fopen(outname, "w"); 
     if(fblob==NULL) 
      error("unable to open target file"); 

     if(fwrite(blobmem, blobsize, 1, fblob)!=1) 
      error("unable to write to target file"); 

     fclose(fblob); 
     free(blobmem); 
    } 
    else 
     error("wrong usage"); 

    sqlite3_close(db); 
    return 0; 
} 

为了在图像中存储ID，只需在同一张表中创建另一列即可。

Answer 2

此链接可以帮助你

Reading & Saving images from a database using C#