Win32 位图 - BitBlt，内存兼容DC，LoadBitmap

注：以下内容为学习笔记，多数是从书本、资料中得来，只为加深印象，及日后参考。然而本人表达能力较差，写的不好。因非翻译、非转载，只好选原创，但多数乃摘抄，实为惭愧。但若能帮助一二访客，幸甚！

学了一周左右的Win32 SDK编程，已经不可抑制的想要自己写点什么了，鉴于以往学Qt时自己编写小游戏的乐趣，决定再把那几个小游戏用Win32 SDK实现一遍。现在万事俱备只欠东风了，再学一下位图的显式吧~~，这几章内容真多，一切从简吧。

1. BitBlt

BitBlt(hdcDst, xDst, yDst, cx, cy, hdcSrc, xSrc, ySrc, dwROP);

该函数把像素从一个设备（叫做“源”）的矩形区域，传输到另一个设备环境（也就是“目标”）中一个同样大小的矩形区域。源和目标可以使一样的。

下面把屏幕的左上角256*256区域拷贝到客户区：

/*-----------------------------------------------------------
   BitBlt.cpp -- BitBlt Demonstration
------------------------------------------------------------*/

#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
	static TCHAR szAppName[] = TEXT("BitBlt");
	HWND         hwnd;
	MSG          msg;
	WNDCLASS     wndclass;

	wndclass.style         = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc   = WndProc;
	wndclass.cbClsExtra    = 0;
	wndclass.cbWndExtra    = 0;
	wndclass.hInstance     = hInstance;
	wndclass.hIcon         = LoadIcon(NULL, IDI_INFORMATION);
	wndclass.hCursor       = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject (WHITE_BRUSH);
	wndclass.lpszMenuName  = NULL;
	wndclass.lpszClassName = szAppName;

	if (!RegisterClass (&wndclass))
	{
	MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR);
	return 0 ;
	}

	hwnd = CreateWindow(szAppName, TEXT ("BitBlt Demo"),
					    WS_OVERLAPPEDWINDOW,
					    CW_USEDEFAULT, CW_USEDEFAULT,
					    CW_USEDEFAULT, CW_USEDEFAULT,
					    NULL, NULL, hInstance, NULL);

	ShowWindow(hwnd, iCmdShow);
	UpdateWindow(hwnd);

	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return msg.wParam;
}


LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static int			cxClient, cyClient, cxSource, cySource;
	HDC					hdcClient, hdcScreen;
	PAINTSTRUCT			ps;
	int					x, y;

	switch (message)
	{
	case WM_CREATE:
		/*cxSource = GetSystemMetrics(SM_CXSIZEFRAME) + GetSystemMetrics(SM_CXSIZE);
		cySource = GetSystemMetrics(SM_CYSIZEFRAME) + GetSystemMetrics(SM_CYCAPTION);*/

		cxSource = 256;
		cySource = 256;

		return 0;

	case WM_SIZE:
		cxClient = LOWORD(lParam);
		cyClient = HIWORD(lParam);
		
		return 0;

	case WM_PAINT:
		hdcClient = BeginPaint(hwnd, &ps);
		hdcScreen = CreateDC(TEXT("DISPLAY"), NULL, NULL, NULL);

		for (y = 0; y < cyClient; y += cySource)
			for (x = 0; x < cxClient; x += cxSource)
			{
				BitBlt(hdcClient, x, y, cxSource, cySource, hdcScreen, 0, 0, SRCCOPY);
			}

		DeleteDC(hdcScreen);
		EndPaint(hwnd, &ps);
		return 0;

	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hwnd, message, wParam, lParam);
}

2.内存设备环境

通常，设备环境对应于特定的图形输出设备和驱动程序。内存设备环境只存在于内存。它不是一个真实的图形输出设备，但和特定的真实设备“兼容”。

要创建一个内存设备环境，必须有一个对应于真实设备的设备句柄。

hdcMem = CreateCompatibleDC(hdc);

把GDI位图对象选入内存设备环境：

SelectObject(hdcMem, hBitmap);

3.加载位图资源

hBitmap = LoadBitmap(hInstance, szBitmapName);

示例：

/*-----------------------------------------------------------
   Bricks1.cpp -- LoadBitmap Demostration
------------------------------------------------------------*/

#include <windows.h>
#include "resource.h"

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
	static TCHAR szAppName[] = TEXT("Bricks1");
	HWND         hwnd;
	MSG          msg;
	WNDCLASS     wndclass;

	wndclass.style         = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc   = WndProc;
	wndclass.cbClsExtra    = 0;
	wndclass.cbWndExtra    = 0;
	wndclass.hInstance     = hInstance;
	wndclass.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor       = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject (WHITE_BRUSH);
	wndclass.lpszMenuName  = NULL;
	wndclass.lpszClassName = szAppName;

	if (!RegisterClass (&wndclass))
	{
	MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR);
	return 0 ;
	}

	hwnd = CreateWindow(szAppName, TEXT ("LoadBitmap Demo"),
					    WS_OVERLAPPEDWINDOW,
					    CW_USEDEFAULT, CW_USEDEFAULT,
					    CW_USEDEFAULT, CW_USEDEFAULT,
					    NULL, NULL, hInstance, NULL);

	ShowWindow(hwnd, iCmdShow);
	UpdateWindow(hwnd);

	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return msg.wParam;
}


LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static HBITMAP		hBitmap;
	static int			cxClient, cyClient, cxSource, cySource;
	BITMAP				bitmap;
	HDC					hdc, hdcMem;
	PAINTSTRUCT			ps;
	int					x, y;
	HINSTANCE			hInstance;

	switch (message)
	{
	case WM_CREATE:
		hInstance = ((LPCREATESTRUCT)lParam)->hInstance;

		hBitmap = LoadBitmap(hInstance,  MAKEINTRESOURCE(IDB_BITMAP1));

		GetObject(hBitmap, sizeof(BITMAP), &bitmap);

		cxSource = bitmap.bmWidth;
		cySource = bitmap.bmHeight;

		return 0;

	case WM_SIZE:
		cxClient = LOWORD(lParam);
		cyClient = HIWORD(lParam);
		
		return 0;

	case WM_PAINT:
		hdc = BeginPaint(hwnd, &ps);
		hdcMem = CreateCompatibleDC(hdc);
		SelectObject(hdcMem, hBitmap);

		for (y = 0; y < cyClient; y += cySource)
			for (x = 0; x < cxClient; x += cxSource)
			{
				BitBlt(hdc, x, y, cxSource, cySource, hdcMem, 0, 0, SRCCOPY);
			}

		DeleteDC(hdcMem);
		EndPaint(hwnd, &ps);
		return 0;

	case WM_DESTROY:
		DeleteObject(hBitmap);
		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hwnd, message, wParam, lParam);
}

上面的例子使用了位图资源。