Saving Image to Memory | 易学教程

问题

I have an dev-c++ Application which makes an Screenshot and writes it into an File. Now I want to write the image into an Variable/Stream. Originally I used three Writefile Functions, which write the header, the info and the hbitmap into an file. Now I want to save the data not to the file, but to an Stream, so I can use it for further processing. The Code I use is this:

/* <Include> */
#include <windows.h>
#include <iostream>
#include <sstream>
/* </Include> */

/* <Const> */
const char *AppName="Yeah";
using namespace std;
/* </Const> */

/* <Function> */
void SaveScreen(HWND pScreen, stringstream Path)
{
    int     Width  = GetSystemMetrics(SM_CXSCREEN);//1280;
    int     Height = GetSystemMetrics(SM_CYSCREEN);//1024;

    HDC hdcScreen;
    HBITMAP hbmScreen;


    //---------------Bitmap Informationen
    BITMAPINFO infobmp;
    infobmp.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    infobmp.bmiHeader.biWidth = Width;
    infobmp.bmiHeader.biHeight = Height;
    infobmp.bmiHeader.biPlanes = 1;
    infobmp.bmiHeader.biBitCount = 24;
    infobmp.bmiHeader.biCompression = 0;
    infobmp.bmiHeader.biSizeImage = 0;
    infobmp.bmiHeader.biXPelsPerMeter = 0;
    infobmp.bmiHeader.biYPelsPerMeter = 0;
    infobmp.bmiHeader.biClrUsed = 0;
    infobmp.bmiHeader.biClrImportant = 0;

    int* bitmap = new int[Width*Height*3];

    BITMAPFILEHEADER bfheader;

    bfheader.bfType = 19778;
    bfheader.bfSize = sizeof(BITMAPFILEHEADER) + Width*Height*3 + sizeof(BITMAPINFOHEADER);
    bfheader.bfReserved1 = 0;
    bfheader.bfReserved2 = 0;
    bfheader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    //Bitmap -----------------------      Informationen


    hdcScreen = GetWindowDC(pScreen);
    hbmScreen = CreateCompatibleBitmap(hdcScreen, Width, Height);

    // tempor?rer DC
    HDC hdcTemp = CreateCompatibleDC(hdcScreen);

    // Bitmap reinselektieren
    HBITMAP hbmOld = (HBITMAP)SelectObject(hdcTemp, hbmScreen);

    // Inhalt von Desktop ?bertragen
    BitBlt(hdcTemp, 0, 0, Width, Height, hdcScreen, 0, 0, SRCCOPY);

    int iResult = GetDIBits(hdcTemp, hbmScreen, 0, Height, bitmap, &infobmp, DIB_RGB_COLORS);

    // aufr?umen
    SelectObject(hdcTemp, hbmOld);
    DeleteObject(hbmScreen);
    DeleteDC(hdcTemp);

   // HANDLE hfile = CreateFile(Path, GENERIC_WRITE, 0, 0, OPEN_ALWAYS, 0, 0);

    //Datei Schreiben
    DWORD word;
    WriteFile(Path, &bfheader, 14, &word, NULL);
    WriteFile(Path, &infobmp, 40,& word, NULL);
    WriteFile(Path, bitmap, Width*Height*3, &word,NULL);
//    Path = &bfheader & &infobmp & bitmap;
    ReleaseDC(pScreen, hdcScreen);
//    CloseHandle(hfile);
    delete[] bitmap;
}
/* </Function> */

int WINAPI WinMain(      
    HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    LPSTR lpCmdLine,
    int nCmdShow)
{   
    HWND hWnd = FindWindow(NULL, AppName);


    stringstream ms;
    SaveScreen(hWnd, ms);

    return 0;
}

Can someone please show me what I am doing wrong?

回答1:

You can create a structure like this:

struct ScreenShotBuffer
{
BITMAPFILEHEADER bfheader;
BITMAPINFO infobmp;
int* bitmap;
};

Then create a global variable using that structure.

struct ScreenShotBuffer myScreenShot;

Anyway you are allocating the "memory" to hold the data using malloc. So you can just use these three lines instead of WriteBuffer() :

myScreenShot.bfheader=bfheader;
myScreenShot.infobmp=infobmp;
myScreenShot.bitmap=bitmap;

来源：https://stackoverflow.com/questions/19247396/saving-image-to-memory

标签

c++

variables

stream

dev-c++