#include<windows.h>

//背景
#define BW	640
#define BH	480
//前景
#define FW	500
#define FH	150

//半透明にする色
#define ALPHA 0x00000000

LRESULT CALLBACK WindowProc(HWND hWnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
	HDC hdc;
	PAINTSTRUCT ps;
	//DIB　背景　前景
	static LPDWORD lpPixelB,lpPixelF;
	//DIBSection　完成画像
	static BITMAPINFO bmpInfo;
	static LPDWORD lpPixel;
	static HBITMAP hBitmap;
	static HDC hMemDC;
    //その他
	static BYTE a=50;			//不透明度(0〜100)
	static POINT pt={100,100};	//表示座標
	int x,y;
	BYTE r,g,b;
	RGBQUAD color,colorF;
	char str[64];

	switch(uMsg) {
		case WM_CREATE:
			//DIB作成
			lpPixelB=(LPDWORD)HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,(BW*BH*4)+(FW*FH*4));
			lpPixelF=lpPixelB+BW*BH;
			//DIB(Section)の情報を設定する　完成画像
			bmpInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
			bmpInfo.bmiHeader.biWidth=BW;
			bmpInfo.bmiHeader.biHeight=-BH;		//注意
			bmpInfo.bmiHeader.biPlanes=1;
			bmpInfo.bmiHeader.biBitCount=32;
			bmpInfo.bmiHeader.biCompression=BI_RGB;
			//DIBSection作成			
			hBitmap=CreateDIBSection(NULL,&bmpInfo,DIB_RGB_COLORS,(void**)&lpPixel,NULL,0);
			hMemDC=CreateCompatibleDC(NULL);
			SelectObject(hMemDC,hBitmap);
			//テキストの設定を変更する
			SetTextColor(hMemDC,RGB(255,255,255));
			SetBkMode(hMemDC,TRANSPARENT);
			//画像作成　背景
			for(y=0;y<BH;y++){
				for(x=0;x<BW;x++){
					r=x%256; g=y%256; b=255-r;
					lpPixelB[x+y*BW]=(r<<16)+(g<<8)+b;
				}
			}
			//前景
			for(y=0;y<FH;y++){
				for(x=0;x<FW;x++){
					lpPixelF[x+y*FW]=0x0000ff00;
				}
			}
			for(y=10;y<FH-10;y++){
				for(x=10;x<FW-10;x++){
					lpPixelF[x+y*FW]=ALPHA;
				}
			}
			return 0;
		case WM_DESTROY:
			HeapFree(GetProcessHeap(),0,lpPixelB);
			DeleteDC(hMemDC);
			DeleteObject(hBitmap);
			PostQuitMessage(0);
			return 0;
		case WM_KEYDOWN:
			switch(LOWORD(wParam)){
				case VK_UP: pt.y-=10; break;
				case VK_DOWN: pt.y+=10; break;
				case VK_LEFT: pt.x-=10; break;
				case VK_RIGHT: pt.x+=10; break;
				case VK_ADD: if(a<100){a++;} break;
				case VK_SUBTRACT:if(a>0){a--;} break;
				default: return 0;
			}
			InvalidateRect(hWnd,NULL,FALSE);
			return 0;
		case WM_PAINT:
			hdc=BeginPaint(hWnd,&ps);
			//背景の描画
			CopyMemory(lpPixel,lpPixelB,BW*BH*4);
			//合成　前景×不透明度＋完成画像×(100−不透明度)
			for(y=0;y<FH;y++){
				if(pt.y+y<0 || pt.y+y>=BH) continue;
				for(x=0;x<FW;x++){
					if(pt.x+x<0 || pt.x+x>=BW) continue;

					if(lpPixelF[x+y*FW]==ALPHA){	//半透明処理
						CopyMemory(&colorF,&lpPixelF[x+y*FW],sizeof(RGBQUAD));
						CopyMemory(&color,&lpPixel[(pt.x+x)+(pt.y+y)*BW],sizeof(RGBQUAD));

						r=(BYTE)(colorF.rgbRed*a/100.0 + color.rgbRed*(100-a)/100.0);
						g=(BYTE)(colorF.rgbGreen*a/100.0 + color.rgbGreen*(100-a)/100.0);
						b=(BYTE)(colorF.rgbBlue*a/100.0 + color.rgbBlue*(100-a)/100.0);

						lpPixel[(pt.x+x)+(pt.y+y)*BW]=(r<<16)+(g<<8)+b;
					}else{		//前景そのまま
						lpPixel[(pt.x+x)+(pt.y+y)*BW]=lpPixelF[x+y*FW];
					}
				}
			}
			//文字列描画
			wsprintf(str,"現在の不透明度 %d ％",a);
			TextOut(hMemDC,pt.x+20,pt.y+20,str,(int)strlen(str));
			//表画面へ転送
			BitBlt(hdc,0,0,BW,BH,hMemDC,0,0,SRCCOPY);
			EndPaint(hWnd,&ps);
			return 0;
	}
	return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

int WINAPI WinMain(
	HINSTANCE hInstance,HINSTANCE hPrevInstance,PSTR lpCmdLine,int nCmdShow)
{
	WNDCLASS wc;
	MSG msg;

	wc.style		 = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc	 = WindowProc;
	wc.cbClsExtra	 = 0;
	wc.cbWndExtra	 = 0;
	wc.hInstance	 = hInstance;
	wc.hIcon		 = LoadIcon(NULL,IDI_APPLICATION);
	wc.hCursor		 = LoadCursor(NULL,IDC_ARROW);
	wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wc.lpszMenuName	 = NULL;
	wc.lpszClassName = __FILE__;
	if(!RegisterClass(&wc)) return 0;

	HWND hWnd=CreateWindow(
		__FILE__,"半透明処理",
		WS_OVERLAPPEDWINDOW | WS_VISIBLE,
		CW_USEDEFAULT,CW_USEDEFAULT,
		CW_USEDEFAULT,CW_USEDEFAULT, 
		NULL,NULL,hInstance,NULL);
	if(hWnd==NULL) return 0;

	BOOL bRet;
	while((bRet=GetMessage(&msg,NULL,0,0))!=0){
		if(bRet==-1) break;
		DispatchMessage(&msg);
	}

	return (int)msg.wParam;
}