How to make a screenshot with a C++ application?[•RESOLVED•] - c++

Question

I want to make a program that make a screenshot and save it in a bitmap (bmp file).
I Have this code:
#include <atlsafe.h>
#include <iostream>
#include <windows.h>
#include <vector>
#include <fstream>
#include <atlimage.h>
using namespace std;
void TakeScreenShot(const std::string& path)
{
//setting to the screen shot
keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY, 0);
keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP, 0);
//handler of the bitmap that save the screen shot
HBITMAP hBitmap;
//I have to give for it time to make it work
Sleep(100);
//take the screen shot
OpenClipboard(NULL);
//save the screen shot in the bitmap handler
hBitmap = (HBITMAP)GetClipboardData(CF_BITMAP);
//relese the screen shot
CloseClipboard();
std::vector<BYTE> buf;
IStream* stream = NULL;
HRESULT hr = CreateStreamOnHGlobal(0, TRUE, &stream);
CImage image;
ULARGE_INTEGER liSize;
// screenshot to jpg and save to stream
image.Attach(hBitmap);
image.Save(stream, Gdiplus::ImageFormatJPEG);
IStream_Size(stream, &liSize);
DWORD len = liSize.LowPart;
IStream_Reset(stream);
buf.resize(len);
IStream_Read(stream, &buf[0], len);
stream->Release();
// put the imapge in the file
std::fstream fi;
fi.open(path, std::fstream::binary | std::fstream::out);
fi.write(reinterpret_cast<const char*>(&buf[0]), buf.size() * sizeof(BYTE));
fi.close();
}
int main()
{
string path = "C:\\";
TakeScreenShot(path);
return 0;
}
First thing I want to say is that i'm approaching windows graphics in C++ for the first time, that's my first program that make screenshots
This program doesn't give me errors but, during the debug, i gives me an error in the "atlimage.h" file,
error:
>Expression: hBitmap != 0
How can I fix that? I think that the real problem is when it has to save the screenshot in the file.
(I think that because while writing this question on stackoverflow I accidentally pressed "Ctrl + V" and stackoverflow detected an image...The program basically do what it has to do but not completely because it doesn't save screenshot on a file, it saves the screenshot in the clipboard :/ )
EDIT:
I tried with this other code:
#include <atlsafe.h>
#include <iostream>
#include <windows.h>
#include <vector>
#include <fstream>
#include <atlimage.h>
#include <string>
using namespace std;
void TakeScreenShot(const std::string& path, POINT a, POINT b)
{
//setting to the screen shot
keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY, 0);
keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP, 0);
HDC hScreen = GetDC(NULL);
//handler of the bitmap that save the screen shot
HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, abs(b.x - a.x), abs(b.y - a.y));;
//I have to give for it time to make it work
Sleep(100);
//take the screen shot
OpenClipboard(NULL);
EmptyClipboard();
//save the screen shot in the bitmap handler
SetClipboardData(CF_BITMAP, hBitmap);
//relese the screen shot
CloseClipboard();
std::vector<BYTE> buf;
IStream* stream = NULL;
HRESULT hr = CreateStreamOnHGlobal(0, TRUE, &stream);
CImage image;
ULARGE_INTEGER liSize;
// screenshot to jpg and save to stream
image.Attach(hBitmap);
image.Save(stream, Gdiplus::ImageFormatJPEG);
IStream_Size(stream, &liSize);
DWORD len = liSize.LowPart;
IStream_Reset(stream);
buf.resize(len);
IStream_Read(stream, &buf[0], len);
stream->Release();
// put the imapge in the file
std::fstream fi;
fi.open(path, std::fstream::binary | std::fstream::out);
fi.write(reinterpret_cast<const char*>(&buf[0]), buf.size() * sizeof(BYTE));
fi.close();
}
int main()
{
string path = "out.jpg";
POINT a, b;
a.x = 0;
a.y = 0;
b.x = 800;
b.y = 800;
TakeScreenShot(path,a,b);
return 0;
}
And it seems it works, it saves the file and doesn't give any error.
The problem is that the out.jpg file is completely black :/. I think there is an error in the File save instructions. Anyone can help me?
EDIT 2:
I have resolved the problem :D
Now I have this code:
#include <atlsafe.h>
#include <iostream>
#include <windows.h>
#include <vector>
#include <fstream>
#include <atlimage.h>
using namespace std;
void TakeScreenShot(const std::string& path)
{
//setting to the screen shot
keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY, 0);
keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP, 0);
//handler of the bitmap that save the screen shot
HBITMAP hBitmap;
//I have to give for it time to make it work in pratica guarda
Sleep(1000); //Modified
//take the screen shot
OpenClipboard(NULL);
//save the screen shot in the bitmap handler
hBitmap = (HBITMAP)GetClipboardData(CF_BITMAP);
//relese the screen shot
CloseClipboard();
std::vector<BYTE> buf;
IStream* stream = NULL;
HRESULT hr = CreateStreamOnHGlobal(0, TRUE, &stream);
CImage image;
ULARGE_INTEGER liSize;
// screenshot to jpg and save to stream
image.Attach(hBitmap);
image.Save(stream, Gdiplus::ImageFormatJPEG);
IStream_Size(stream, &liSize);
DWORD len = liSize.LowPart;
IStream_Reset(stream);
buf.resize(len);
IStream_Read(stream, &buf[0], len);
stream->Release();
// put the imapge in the file
std::fstream fi;
fi.open(path, std::fstream::binary | std::fstream::out);
fi.write(reinterpret_cast<const char*>(&buf[0]), buf.size() * sizeof(BYTE));
fi.close();
}
int main()
{
string path = "sus.jpg";
TakeScreenShot(path);
cout << "Calling TakeScreenShot function..." << endl; //added
Sleep(3000); //added
return 0;
}
I just added the last part with the cout and upped the stop time on line 21 from 100ms to 1000ms.
Enjoy my experience with this program :)