在WinCE中, 由于WinCE的精簡,有很多win32下的標準API不支持,所以有很多在vc上能夠輕易實現(xiàn)的功能, 在evc中有點難度,必須變通一下,就拿截取屏幕來說,一個常用的函數(shù)GetDIBits在wince就Unsupported.當時為了實現(xiàn)這個功能,頗費了了一番心血，當然其主要還是因為對api不是很熟悉。
最初使用的截屏方法說來還真有些丟人，一個一個點的取得顏色值，再保存到bmp文件中去，這樣程序運行的速度超慢，保存一個800X600的bmp差不多要一兩分鐘（研華8251板），覺得有些不對頭，決定想辦法改進一下，就使勁地看了一下Charles Petzold先生的《Programming Windows》（這本書很經(jīng)典，值得好好研究一下），終于把時間縮短到幾秒鐘了，下面這個函數(shù)在evc和vc下都test pass(不用更改)，有不足之處歡迎指正，函數(shù)：
// this function create a bmp file to save the current screen;
// supported eVC++ 4.0 (wince 4.0) and vc++ 6.0 , test pass;
void CSnapDlg::OnScreenSave(const char *filename)
{
HDC hScrDC, hMemDC;
int width, height;
//the pointer will save all pixel point's color value
BYTE *lpBitmapBits = NULL;
//creates a device context for the screen device
hScrDC = CreateDC(_T("DISPLAY"), NULL, NULL, NULL);
//get the screen point size
width = GetDeviceCaps(hScrDC, HORZRES);
height = GetDeviceCaps(hScrDC, VERTRES);
//creates a memory device context (DC) compatible with the screen device(hScrDC)
hMemDC = CreateCompatibleDC(hScrDC);
//initialise the struct BITMAPINFO for the bimap infomation，
//in order to use the function CreateDIBSection
// on wince os, each pixel stored by 24 bits(biBitCount=24)
//and no compressing(biCompression=0)
BITMAPINFO RGB24BitsBITMAPINFO;
ZeroMemory(&RGB24BitsBITMAPINFO, sizeof(BITMAPINFO));
RGB24BitsBITMAPINFO.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
RGB24BitsBITMAPINFO.bmiHeader.biWidth = width;
RGB24BitsBITMAPINFO.bmiHeader.biHeight = height;
RGB24BitsBITMAPINFO.bmiHeader.biPlanes = 1;
RGB24BitsBITMAPINFO.bmiHeader.biBitCount = 24;
//use the function CreateDIBSection and SelectObject
//in order to get the bimap pointer : lpBitmapBits
HBITMAP directBmp = CreateDIBSection(hMemDC, (BITMAPINFO*)&RGB24BitsBITMAPINFO,
DIB_RGB_COLORS, (void **)&lpBitmapBits, NULL, 0);
HGDIOBJ previousObject = SelectObject(hMemDC, directBmp);
// copy the screen dc to the memory dc
BitBlt(hMemDC, 0, 0, width, height, hScrDC, 0, 0, SRCCOPY);
//if you only want to get the every pixel color value,
//you can begin here and the following part of this function will be unuseful;
//the following part is in order to write file;
//bimap file header in order to write bmp file
BITMAPFILEHEADER bmBITMAPFILEHEADER;
ZeroMemory(&bmBITMAPFILEHEADER, sizeof(BITMAPFILEHEADER));
bmBITMAPFILEHEADER.bfType = 0x4d42; //bmp
bmBITMAPFILEHEADER.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
bmBITMAPFILEHEADER.bfSize = bmBITMAPFILEHEADER.bfOffBits + ((width*height)*3); ///3=(24 / 8)
//write into file
FILE *mStream = NULL;
if((mStream = fopenfilename, "wb")))
{
//write bitmap file header
fwrite(&bmBITMAPFILEHEADER, sizeof(BITMAPFILEHEADER), 1, mStream);
//write bitmap info
fwrite(&(RGB24BitsBITMAPINFO.bmiHeader), sizeof(BITMAPINFOHEADER), 1, mStream);
//write bitmap pixels data
fwrite(lpBitmapBits, 3*width*height, 1, mStream);
//close file
fclose(mStream);
}
//delete
DeleteObject(hMemDC);
DeleteObject(hScrDC);
DeleteObject(directBmp);
DeleteObject(previousObject);
}
還是用英語作了注釋，雖然英語學的很糟糕，還是覺得這個習慣比較好~~ ..