Creating and Saving a Bitmap

[TheBeast32]

Hi, I am making a simple screen shot program. I need to be able to capture the entire screen, or if possible, a region of the screen (like a rectangle from point (25, 60) to (300, 456)). I also need to be able to save it to a bitmap file. I read a tutorial, but it only said how to save black and white bitmaps. I need them to be in color.

[William Hemsworth]

I found this code on the web some time ago and saved it. It seems to do exactly what you want :) Heres a quick example of how to save the top left corner of the screen.

#include<iostream>
#include<windows.h>
using namespace std;

inline int GetFilePointer(HANDLE FileHandle){
	return SetFilePointer(FileHandle, 0, 0, FILE_CURRENT);
}

bool SaveBMPFile(char *filename, HBITMAP bitmap, HDC bitmapDC, int width, int height){
	bool Success=0;
	HDC SurfDC=NULL;
	HBITMAP OffscrBmp=NULL;
	HDC OffscrDC=NULL;
	LPBITMAPINFO lpbi=NULL;
	LPVOID lpvBits=NULL;
	HANDLE BmpFile=INVALID_HANDLE_VALUE;
	BITMAPFILEHEADER bmfh;
	if ((OffscrBmp = CreateCompatibleBitmap(bitmapDC, width, height)) == NULL)
		return 0;
	if ((OffscrDC = CreateCompatibleDC(bitmapDC)) == NULL)
		return 0;
	HBITMAP OldBmp = (HBITMAP)SelectObject(OffscrDC, OffscrBmp);
	BitBlt(OffscrDC, 0, 0, width, height, bitmapDC, 0, 0, SRCCOPY);
	if ((lpbi = (LPBITMAPINFO)(new char[sizeof(BITMAPINFOHEADER) + 256 * sizeof(RGBQUAD)])) == NULL) 
		return 0;
	ZeroMemory(&lpbi->bmiHeader, sizeof(BITMAPINFOHEADER));
	lpbi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	SelectObject(OffscrDC, OldBmp);
	if (!GetDIBits(OffscrDC, OffscrBmp, 0, height, NULL, lpbi, DIB_RGB_COLORS))
		return 0;
	if ((lpvBits = new char[lpbi->bmiHeader.biSizeImage]) == NULL)
		return 0;
	if (!GetDIBits(OffscrDC, OffscrBmp, 0, height, lpvBits, lpbi, DIB_RGB_COLORS))
		return 0;
	if ((BmpFile = CreateFile(filename,
						GENERIC_WRITE,
						0, NULL,
						CREATE_ALWAYS,
						FILE_ATTRIBUTE_NORMAL,
						NULL)) == INVALID_HANDLE_VALUE)
		return 0;
	DWORD Written;
	bmfh.bfType = 19778;
	bmfh.bfReserved1 = bmfh.bfReserved2 = 0;
	if (!WriteFile(BmpFile, &bmfh, sizeof(bmfh), &Written, NULL))
		return 0;
	if (Written < sizeof(bmfh)) 
		return 0; 
	if (!WriteFile(BmpFile, &lpbi->bmiHeader, sizeof(BITMAPINFOHEADER), &Written, NULL)) 
		return 0;
	if (Written < sizeof(BITMAPINFOHEADER)) 
		return 0;
	int PalEntries;
	if (lpbi->bmiHeader.biCompression == BI_BITFIELDS) 
		PalEntries = 3;
	else PalEntries = (lpbi->bmiHeader.biBitCount <= 8) ?
					  (int)(1 << lpbi->bmiHeader.biBitCount) : 0;
	if(lpbi->bmiHeader.biClrUsed) 
	PalEntries = lpbi->bmiHeader.biClrUsed;
	if(PalEntries){
	if (!WriteFile(BmpFile, &lpbi->bmiColors, PalEntries * sizeof(RGBQUAD), &Written, NULL)) 
		return 0;
		if (Written < PalEntries * sizeof(RGBQUAD)) 
			return 0;
	}
	bmfh.bfOffBits = GetFilePointer(BmpFile);
	if (!WriteFile(BmpFile, lpvBits, lpbi->bmiHeader.biSizeImage, &Written, NULL)) 
		return 0;
	if (Written < lpbi->bmiHeader.biSizeImage) 
		return 0;
	bmfh.bfSize = GetFilePointer(BmpFile);
	SetFilePointer(BmpFile, 0, 0, FILE_BEGIN);
	if (!WriteFile(BmpFile, &bmfh, sizeof(bmfh), &Written, NULL))
		return 0;
	if (Written < sizeof(bmfh)) 
		return 0;
	return 1;
}
bool ScreenCapture(int x, int y, int width, int height, char *filename){
	HDC hDc = CreateCompatibleDC(0);    
	HBITMAP hBmp = CreateCompatibleBitmap(GetDC(0), width, height);   
	SelectObject(hDc, hBmp);   
	BitBlt(hDc, 0, 0, width, height, GetDC(0), x, y, SRCCOPY);  
	bool ret = SaveBMPFile(filename, hBmp, hDc, width, height); 
	DeleteObject(hBmp);  
	return ret;
}

int main() {
	ScreenCapture(0, 0, 100, 100, "picture.bmp");
	cin.ignore();
	return 0;
}

[William Hemsworth]

Here is the code to take a full screenshot. The only problem is the bitmap is completely uncompressed and can be 4mb+ just off one screenshot. The next part would be to figure out how to compress the bitmap.

int main() {
	int x1 = 0;
	int y1 = 0;
	int x2 = GetSystemMetrics(SM_CXSCREEN);
	int y2 = GetSystemMetrics(SM_CYSCREEN);
	ScreenCapture(x1, y1, x2 - x1, y2 - y1, "picture.bmp");
	cin.ignore();
	return 0;
}

[marco93]

The method is wrong.
Save it in jpeg, gif or png.
You can ask on specialized win32 api newsgroup :
news://194.177.96.26/comp.os.ms-windows.programmer.win32
where it's a FAQ...

[William Hemsworth]

The method is wrong.
Save it in jpeg, gif or png.
You can ask on specialized win32 api newsgroup :
news://194.177.96.26/comp.os.ms-windows.programmer.win32
where it's a FAQ...

Tell me, in what way is it wrong ??..

[TheBeast32]

Thanks for your help! Also, marco93, It's only 1 picture, i'm not going to take 5000. And, it works so i'm happy. =)