DirectDraw Surface 알파블랜딩 - DirectDraw Surface Alpha Blending

HBITMAP m_hbm;
BITMAP m_bmpInfo;
...

< 비트맵 로드 - bitmap load >


m_hbm = (HBITMAP) LoadImage(GetModuleHandle(NULL), MAKEINTRESOURCE(123), IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION);
GetObject(m_hbm, sizeof(m_bmpInfo), &m_bmpInfo);

< 알파블랜딩 - alpha blending >

void drawBitmapAlpha(RECT *rectTarget, IDirectDrawSurface7 *lpSurface)

{

HDC hdc;

if (lpSurface->GetDC(&hdc) != DD_OK || m_hbm == NULL)

return;

/* calculate bitmap size */

int targetWidth = rectTarget->right-rectTarget->left;

int targetHeight = rectTarget->bottom-rectTarget->top;

int cx = rectTarget->left+targetWidth/2;

int cy = rectTarget->top+targetHeight/2;

int bmpWidth = m_bmpInfo.bmWidth;

int bmpHeight = m_bmpInfo.bmHeight;

POINT pt;

pt.x = cx-bmpWidth/2;

pt.y = cy-bmpHeight/2;

HDC hMemDC, hAlphaDC;

BOOL ret;

hMemDC = CreateCompatibleDC(hdc);    // create bitmap dc

hAlphaDC = CreateCompatibleDC(hdc);    // create alpha dc

HBITMAP hbmAlpha = CreateCompatibleBitmap(hdc, bmpWidth, bmpHeight);

SelectObject(hMemDC, m_hbm);

SelectObject(hAlphaDC, hbmAlpha);

 

        // copy src image to alpha dc

ret = BitBlt(hAlphaDC, 0, 0, bmpWidth, bmpHeight, hdc, pt.x, pt.y, SRCCOPY);

if (!ret) {

TRACE("[%s] BitBlt failed, err:%d\n", __FUNCTION__, GetLastError());

}

        // copy bitmap image to alpha dc with transparent

ret = TransparentBlt(hAlphaDC, 0, 0, bmpWidth, bmpHeight, hMemDC, 0, 0, m_bmpInfo.bmWidth, m_bmpInfo.bmHeight, RGB(0, 0, 0));

if (!ret) {

TRACE("[%s] TransparentBlt failed, err:%d\n", __FUNCTION__, GetLastError());

}

BLENDFUNCTION bf;

bf.BlendOp = AC_SRC_OVER;

bf.BlendFlags = 0;

bf.SourceConstantAlpha = 100;

bf.AlphaFormat = 0;

        // alpha blend alpha dc to dest dc

ret = AlphaBlend(hdc, pt.x, pt.y, bmpWidth, bmpHeight, hAlphaDC, 0, 0, bmpWidth, bmpHeight, bf);

if (!ret) {

TRACE("[%s] AlphaBlend failed, err:%d\n", __FUNCTION__, GetLastError());

}

DeleteObject(hbmAlpha);

DeleteDC(hAlphaDC);

DeleteDC(hMemDC);

lpSurface->ReleaseDC(hdc);

}