MFC 屏幕截图（libjpeg bmp转jpg）

项目中需要用到的功能。

void Screenshot()

{

    CDC *pDC;

    pDC = CDC::FromHandle(GetDC(GetDesktopWindow()));

    if(pDC == NULL)

        return;

    int BitPerPixel = pDC->GetDeviceCaps(BITSPIXEL);

    int Width = pDC->GetDeviceCaps(HORZRES);

    int Height = pDC->GetDeviceCaps(VERTRES);

    CDC memDC;

    if(memDC.CreateCompatibleDC(pDC) == )

        return;

    CBitmap memBitmap, *oldmemBitmap;

    if(memBitmap.CreateCompatibleBitmap(pDC, Width, Height) == NULL)

        return;

    oldmemBitmap = memDC.SelectObject(&memBitmap);

    if(oldmemBitmap == NULL)

        return;

    if(memDC.BitBlt(, , Width, Height, pDC, , , SRCCOPY) == )

        return;

    CPoint po;

    GetCursorPos(&po);

    HICON hinco = (HICON)GetCursor();

    memDC.DrawIcon(po.x- , po.y -  , hinco);

    BITMAP bmp;

    memBitmap.GetBitmap(&bmp);

    BITMAPINFOHEADER bih = {};

    bih.biBitCount = bmp.bmBitsPixel;

    bih.biCompression = BI_RGB;

    bih.biHeight = bmp.bmHeight;

    bih.biPlanes = ;

    bih.biSize = sizeof(BITMAPINFOHEADER);

    bih.biSizeImage = bmp.bmWidthBytes * bmp.bmHeight;

    bih.biWidth = bmp.bmWidth;

    BITMAPFILEHEADER bfh = {};

    bfh.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    bfh.bfSize = bfh.bfOffBits + bmp.bmWidthBytes * bmp.bmHeight;

    bfh.bfType = (WORD)0x4d42;

    BYTE* pImgBuff = new BYTE[bmp.bmWidthBytes * bmp.bmHeight];

    GetDIBits(memDC.m_hDC, (HBITMAP) memBitmap.m_hObject

        , , Height, pImgBuff, (LPBITMAPINFO) &bih, DIB_RGB_COLORS);

    memDC.SelectObject(oldmemBitmap);

    BYTE* pJpg = NULL;

    int nJpgSize = BmpToJpeg(pImgBuff, bmp.bmWidth, bmp.bmHeight, &pJpg);

    if (NULL != pJpg)

    {

        delete[] pJpg;

    }

    delete [] pImgBuff;

}

附上 BmpToJpeg

int BmpToJpeg(BYTE *pSrc, int nWidth, int nHeight, BYTE** ppDes)

{

    struct jpeg_compress_struct cinfo;

    struct jpeg_error_mgr jerr;

    JSAMPROW row_pointer[];

    int row_stride;

    cinfo.err = jpeg_std_error(&jerr);

    jpeg_create_compress(&cinfo);

    DWORD dwLen = nWidth * nHeight * ;

    jpeg_mem_dest(&cinfo, ppDes, &dwLen);

    cinfo.image_width = nWidth;

    cinfo.image_height = nHeight;

    cinfo.input_components = ;

    cinfo.in_color_space = JCS_RGB;

    jpeg_set_defaults(&cinfo);

    jpeg_set_quality(&cinfo, JPEG_QUALITY, TRUE);

    jpeg_start_compress(&cinfo, TRUE);

    row_stride = nWidth * ;

    for (int i=, j=; j < nWidth*nHeight*; i+=, j+=)    //BGRA => RGB

    {

        *(pSrc+i)=*(pSrc+j+);

        *(pSrc+i+)=*(pSrc+j+);

        *(pSrc+i+)=*(pSrc+j);

    }

    while (cinfo.next_scanline < cinfo.image_height)

    {

        row_pointer[] = &pSrc[(cinfo.image_height - cinfo.next_scanline - ) * row_stride];

        (void) jpeg_write_scanlines(&cinfo, row_pointer, );

    }

    jpeg_finish_compress(&cinfo);

    jpeg_destroy_compress(&cinfo);

    return dwLen;

}

需要用到的头文件

#define JPEG_QUALITY 50

extern "C"

{

#include "jpeglib.h"

#include "jmorecfg.h"

#include "jconfig.h"

}