#include<windows.h>

#define WIDTH		197
#define HEIGHT		100
#define BITCOUNT	16

//8ビットを5ビットに近似する
//本質：bit8/(255.0/31.0)
#define TO85(bit8)	((BYTE)(bit8*31.0/255.0+0.5))

//5ビットを8ビットに変換する
#define TO58(bit5)	((BYTE)(bit5*255.0/31.0+0.5))

LRESULT CALLBACK WindowProc(HWND hWnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
	HDC hdc;
	PAINTSTRUCT ps;
	static LPWORD lpPixel;
	static BITMAPINFO bmpInfo;
	int x,y,r,g,b,rgb;
	static int length;

	switch(uMsg) {
		case WM_CREATE:
			//4の倍数に補正
			if(WIDTH*(BITCOUNT/8)%4) length=WIDTH*(BITCOUNT/8)+(4-WIDTH*(BITCOUNT/8)%4);
			else length=WIDTH*(BITCOUNT/8);

			lpPixel=(LPWORD)HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,length*HEIGHT);
			//DIBの情報を設定する
			bmpInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
			bmpInfo.bmiHeader.biWidth=WIDTH;
			bmpInfo.bmiHeader.biHeight=HEIGHT;
			bmpInfo.bmiHeader.biPlanes=1;
			bmpInfo.bmiHeader.biBitCount=BITCOUNT;
			bmpInfo.bmiHeader.biCompression=BI_RGB;
			//描画
			r=TO85(255); g=TO85(128); b=0; rgb=(r<<10)+(g<<5)+b;
			for(y=25;y<=50;y++){
				for(x=25;x<=50;x++){					
					CopyMemory((LPBYTE)lpPixel+x*2+y*length,&rgb,2);
				}	//(255,128,0)8 → (31,16,0)5 → (255,132,0)8
			}
			return 0;
		case WM_DESTROY:
			HeapFree(GetProcessHeap(),0,lpPixel);
			PostQuitMessage(0);
			return 0;
		case WM_PAINT:
			hdc=BeginPaint(hWnd,&ps);
			//表画面へ転送
			StretchDIBits(hdc,0,0,WIDTH,HEIGHT,
				0,0,WIDTH,HEIGHT,lpPixel,&bmpInfo,DIB_RGB_COLORS,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__,"16ビットDIBを作る",
		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;
}