How to download an image from an URL to a local dir? - c++

Question

I'm using C++ without .NET on Win32, how can I download an image over HTTP from a website without having to re-invent the wheel? Is there an API or library that provides a single function to do this?
http://mywebsite/file.imgext --> C:\path\to\dir\file.imgext

Answer 1

WinInet APIs are easier than you think
Here is a complete win32 console program. Can be built with with VS 2010 Express and down loading windows SDK to get WinInit.
// imaged.cpp : Defines the entry point for the console application.
//
// Copy file from internet onto local file
// Uses Wininet API
// program takes 1 mandatory command line argument - URL string
// it downloads ito the current directory, or whatever is passed
// as the second parameter to DownloadURLImage.
// optional parameter, the name of the file (excluding path), by default it uses the
// filename from the URL string.
#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <WinInet.h> // from SDK
#include "string.h"
//#include<TCHAR.H>
//#include "Tchar.h"
using namespace std ;
int convertURLtofname (TCHAR * szURL, TCHAR * szname )
// extract the filename from the URL
{
char aszfilename [100];
HRESULT result;
char achar[3], aszURL [100];
size_t nchars, i, j;
int fresult;
fresult = 0;
nchars= _tcslen(szURL);
i= nchars -1;
while ((i > 0) && (szURL[i] != '/') && (szURL[i] != '\\')) {i--;}
j= 0; i++;
while (i < nchars) { szname [j++]= szURL[i++]; }
szname[j]=_T('\0');
// wcstombs ( aszfilename, szname, 100 );
// cout << aszfilename << endl;
//----------------------------------------------
return fresult ;
}
int determinepathfilename (TCHAR * szURL, TCHAR * szpath, TCHAR * szname, TCHAR * szpathfilename)
{
// use path and filename when supplied. If filename (e.g. funkypic.jpg) is not supplied, then the
// filename will be extracted from the last part of the URL
int result ;
result= 0;
TCHAR szname_copy [100] ;
if ((szname == NULL) || (szname[0] == '\0'))
convertURLtofname (szURL, szname_copy);
else
_tcscpy (szname_copy, szname);
if ((szpath == NULL) || (szpath[0] == '\0'))
_tcscpy (szpathfilename, szname_copy);
else
{
_tcscpy (szpathfilename, szpath);
_tcscat (szpathfilename, szname_copy);
}
return result ;
}
bool GetFile (HINTERNET hOpen, // Handle from InternetOpen()
TCHAR *szURL, // Full URL
TCHAR * szpath,
TCHAR * szname)
{
DWORD dwSize;
TCHAR szHead[15];
BYTE * szTemp[1024];
HINTERNET hConnect;
FILE * pFile;
TCHAR szpathfilename [100] ;
szHead[0] = '\0';
if ( !(hConnect = InternetOpenUrl( hOpen, szURL, szHead, 15, INTERNET_FLAG_DONT_CACHE, 0)))
{
std::cout << "Error: InternetOpenUrl" << std::endl;
return 0;
}
determinepathfilename (szURL, szpath, szname, szpathfilename);
if ( !(pFile = _tfopen (szpathfilename, _T("wb") ) ) )
{
std::cerr << "Error _tfopen" << std::endl;
return false;
}
do
{
// Keep copying in 1024 bytes chunks, while file has any data left.
// Note: bigger buffer will greatly improve performance.
if (!InternetReadFile (hConnect, szTemp, 1024, &dwSize) )
{
fclose (pFile);
std::cerr << "Error InternetReadFile" << std::endl;
return FALSE;
}
if (!dwSize)
break; // Condition of dwSize=0 indicate EOF. Stop.
else
fwrite(szTemp, sizeof (BYTE), dwSize , pFile);
} // do
while (TRUE);
fflush (pFile);
fclose (pFile);
return TRUE;
}
int DownloadURLImage (TCHAR * szURL, TCHAR * szpath, TCHAR * szname)
{ int result ;
HINTERNET hInternet;
result= 0;
hInternet= InternetOpen (_T("imaged"),
INTERNET_OPEN_TYPE_DIRECT, //__in DWORD dwAccessType
NULL, //__in LPCTSTR lpszProxyName,
NULL, //__in LPCTSTR lpszProxyBypass,
NULL //_in DWORD dwFlags
);
GetFile (hInternet, szURL, szpath, szname) ;
InternetCloseHandle(hInternet);
return result ;
}
int _tmain(int argc, _TCHAR* argv[])
{
if (argc == 2)
{
DownloadURLImage (argv[1], NULL, NULL);
//DownloadURLImage (argv[1], _T"C:/", NULL);
}
else if (argc == 3)
{
DownloadURLImage (argv[1], NULL, argv[2]);
//DownloadURLImage (argv[1], _T"C:/", argv[2]);
}
else
{
cout << "Usage: imaged <image URL>" << endl ;
}
system("pause") ;
return 0;
}

Answer 2

You could use cURLpp
I havn't used it yet, but example20 looks like it could solve your problem.

Answer 3

If you want an EASY solution, use this amazingly simple one liner:
system("C:\\Path\\To\\Wget\\wget.exe http://pixelcaster.com/yosemite/webcams/ahwahnee2.jpg -O C:\\Users\\Me\\Desktop\\ahwahnee2.jpg");
With wget for windows
choco install wget
See chocolatey.org

Answer 4

Use Windows Http Services API.

Answer 5

You could use the WinInet or WinHTTP classes in C++. These are native Win32 APIs the abstract some of the work of getting sending and receiving files from the Internet.
I've used WinInet with great success to do just what you're trying to do.

Answer 6

If starting a new process is ok, you could have a look at WGET. (And even if not, the sources are available; you can look there to see how it's been implemented.)

Answer 7

Using POCO for this now. :-)