Edison.X. Blog

這問題實在看了很多人問，但大多是視窗程式還沒學過，只學到 Console 下之程式設計便問要怎麼畫波形圖。在 Console 下畫不是不能畫，可以說是「不習慣」，也可以說是「不好畫」。
這問題我用四種不同方法解過 -
(1) 直接用 Console Mode 上用 printf / cout 去畫，但這個很麻煩
(2) 調用 Console Function 在 Console Window 上畫
(3) 用 Win32 API 去畫
(4) 用 MFC 去畫

這是初步，主要展示取得一個 window handle 後，將其 window 存成 bmp 圖檔。至於要存哪個 window，
可再用 FindWindow 與 FindWindowEx 繼續找下去
 
#include <windows.h>
#include <stdio.h>

void CaptureScreen( HWND hwnd, char *filename)
{
HDC hdcWindow;
HDC hdcMemory;
HBITMAP hBitmap;
BYTE *lpvBits;
BITMAPINFO bi;
BITMAPINFOHEADER bih;
BITMAPFILEHEADER bifh;
HANDLE hFile;
DWORD dwBytesWritten = 0;
DWORD dwSize;
int xSize, ySize;
RECT rect;
hdcWindow = GetDC(NULL);

GetWindowRect(hwnd, &rect);

xSize = rect.right - rect.left;
ySize = rect.bottom - rect.top;
hBitmap = CreateCompatibleBitmap(hdcWindow, xSize, ySize);
hdcMemory = CreateCompatibleDC(hdcWindow);
SelectObject(hdcMemory, hBitmap);
BitBlt(hdcMemory, 0, 0, xSize, ySize,
hdcWindow, rect.left, rect.top, SRCCOPY);

bih.biSize = sizeof(BITMAPINFOHEADER);
bih.biWidth = xSize;
bih.biHeight = ySize;
bih.biPlanes = 1;
bih.biBitCount = 32;
bih.biCompression = BI_RGB;
bih.biSizeImage = 0;
bih.biXPelsPerMeter = 0;
bih.biYPelsPerMeter = 0;
bih.biClrUsed = 0;
bih.biClrImportant = 0;

dwSize = (((xSize * 32 + 31)/32) * 4 * ySize);
lpvBits = (BYTE*)malloc(dwSize);

bifh.bfType = 0x4D42;
bifh.bfSize = sizeof(BITMAPFILEHEADER) +
sizeof(BITMAPINFOHEADER) + dwSize;
bifh.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) +
(DWORD)sizeof(BITMAPINFOHEADER);
bifh.bfReserved1 = 0;
bifh.bfReserved2 = 0;

bi.bmiHeader = bih;

GetDIBits(hdcMemory, hBitmap, 0, (UINT)ySize,
lpvBits, &bi, DIB_RGB_COLORS);
hFile = CreateFile(filename, GENERIC_WRITE, 0,
NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

WriteFile(hFile, (LPSTR)&bifh,
sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)&bih,
sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)lpvBits,
dwSize, &dwBytesWritten, NULL);

DeleteDC(hdcMemory);
DeleteObject(hBitmap);
CloseHandle(hFile);
free(lpvBits);
ReleaseDC(hwnd, hdcWindow);
}

int main()
{
HWND hwnd = GetConsoleWindow();
HWND hdesktop = GetDesktopWindow();
printf("Hello, World!!");
CaptureScreen(hwnd, "D:\\a.bmp"); /* 截取此 console 視窗圖片 */

/* 將此 console 隱藏，避免截取桌面時截到 console window */
// ShowWindow(hwnd, 0);
CaptureScreen(hdesktop, "D:\\desktop.bmp"); /* 截取目前桌面圖片 */
return 0;
}