AlphaBlend 関数を使っておこなえます。
BOOL AlphaBlend(
[in] HDC hdcDest,
[in] int xoriginDest,
[in] int yoriginDest,
[in] int wDest,
[in] int hDest,
[in] HDC hdcSrc,
[in] int xoriginSrc,
[in] int yoriginSrc,
[in] int wSrc,
[in] int hSrc,
[in] BLENDFUNCTION ftn
);
パラメータftnのBLENDFUNCTION構造体は、
typedef struct _BLENDFUNCTION {
BYTE BlendOp; // AC_SRC_OVERのみサポートされています。
BYTE BlendFlags; // 0です。
BYTE SourceConstantAlpha; // ソース ビットマップ全体で使用するアルファ透明度の値を指定します。
BYTE AlphaFormat;
} BLENDFUNCTION, *PBLENDFUNCTION;
この背景に、
このカップを重ねます。
透明度は200です。
〇プログラム例
#pragma comment(lib,"msimg32.lib")
#include <windows.h>
static LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
POINT pt;
LPSTR str = TEXT("こんにちは、日本");
static HDC hMemDC;
static HBITMAP hBitmap, hBackBmp;
static HFONT hFont[2];
LPSTR BitMapFile = TEXT("カップ.bmp");
LPSTR Back_BitMapFile = TEXT("背景.bmp");
static BITMAP bitmap, bitmapBack;
static BLENDFUNCTION blendFunc = { AC_SRC_OVER,0,200,0 };
switch (uMsg)
{
case WM_DESTROY:
DeleteDC(hMemDC);
DeleteObject(hBitmap);
DeleteObject(hBackBmp);
DeleteObject(hFont[0]);
PostQuitMessage(0);
return 0;
case WM_CREATE:
hFont[0] = CreateFont(
40, 0, 0, 0,
FW_NORMAL, FALSE, FALSE, FALSE,
SHIFTJIS_CHARSET, OUT_DEFAULT_PRECIS,
CLIP_DEFAULT_PRECIS, DEFAULT_QUALITY,
VARIABLE_PITCH | FF_DONTCARE, L"メイリオ"
);
ShowWindow(hWnd, SW_SHOW);
hMemDC = CreateCompatibleDC(NULL);
hBitmap = LoadImage(NULL, BitMapFile, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
hBackBmp = LoadImage(NULL, Back_BitMapFile, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
GetObject(hBitmap, sizeof(BITMAP), &bitmap);
GetObject(hBackBmp, sizeof(BITMAP), &bitmapBack);
return 0;
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
//背景の描画
SelectObject(hMemDC, hBackBmp);
BitBlt(hdc, 0, 0, bitmapBack.bmWidth, bitmapBack.bmHeight, hMemDC, 0, 0, SRCCOPY);
pt.x = bitmapBack.bmWidth / 2 - bitmap.bmWidth / 2;
pt.y = bitmapBack.bmHeight - bitmap.bmHeight;
//カップの描画
SelectObject(hMemDC, hBitmap);
AlphaBlend(hdc, pt.x, pt.y, bitmap.bmWidth, bitmap.bmHeight,
hMemDC, 0, 0, bitmap.bmWidth, bitmap.bmHeight,blendFunc);
SelectObject(hdc, hFont[0]);
SetTextColor(hdc, RGB(0, 0xFF, 0));
TextOut(hdc, 0, 0, str, lstrlen(str));
EndPaint(hWnd, &ps);
return 0;
}
return DefWindowProc(hWnd, uMsg, wParam, lParam);
}
int APIENTRY wWinMain(
_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPWSTR ipCmdLine,
_In_ int nCmdShow
) {
WNDCLASSEXW wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = NULL;
wcex.hCursor = NULL;
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wcex.lpszMenuName = NULL;
wcex.lpszClassName = TEXT("TestWindow");
wcex.hIconSm = NULL;
RegisterClassExW(&wcex);
HWND hWnd = CreateWindowEx(0UL, TEXT("TestWindow"), TEXT("日本"), WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, 400, 400, NULL, NULL, hInstance, NULL);
if (!hWnd)
{
return FALSE;
}
MSG msg;
while (GetMessage(&msg, NULL, 0, 0))
{
DispatchMessage(&msg);
}
return (int)msg.wParam;
}