Loading Bitmap Files into DirectDraw
by Kieren Johnstone
载入位图文件到 DirectDraw
译：sea_bug

Introduction
介绍

In this article I will briefly describe the process of using Windows' functions to load a bitmap (.bmp) file of any type, and place it on a newly-created DirectDraw surface. In this particular article, we will be using the DirectX 7.0 SDK. 
在这篇文章里，我将简要叙述一下使用Windows函数来载入任何类型的BMP图象文件数据，并将数据存
放到一个新建立的DirectDraw的表面中。在这以后的篇幅里，我们将使用DirectX 7.0 SDK。

DirectDraw Surface Creation
创建DirectDraw表面

Creating a new DirectDraw surface is very easy, and this function will create a surface of any size. This can also be used as a general-purpose surface creation function, and if you were writing an engine class you'd probably put it in there somewhere. 
创建一个DirectDraw表面是非常容易的，这个函数将根据大小来创建一个表面。这同样能用于多种多
样的表面创建函数，如果你要制作一个引擎类，你也许会把这个放在引擎的某处。

Listing 1
代码列表 1

void CreateSurface(LPDIRECTDRAWSURFACE7 *lpSource, int xs, int ys)
{
    DDSURFACEDESC2 ddsd;

    ZeroMemory(&ddsd, sizeof(ddsd));
    ddsd.dwSize = sizeof(ddsd);
    ddsd.dwFlags = DDSD_CAPS | DDSD_WIDTH | DDSD_HEIGHT;
    ddsd.ddsCaps.dwCaps = DDSCAPS_OFFSCREENPLAIN;
    ddsd.dwWidth = xs;
    ddsd.dwHeight = ys;
    lpdd->CreateSurface(&ddsd, lpSource, NULL);
}


All this code does is create a DDSURFACEDESC2 structure that describes the dimensions of the surface, and tells DirectDraw that it's an off-screen surface. Then, the call to DirectDraw (in this case, DirectDraw is the lpdd pointer) just creates the surface. 
所有的这些代码是为表面建立一个DDSURFACEDESC2的数据结构来记录大小尺度，并且告诉DirectDraw
那是一个离屏表面。然后，呼叫DirectDraw(在这部分，DirectDraw是lpdd的指针)真正创建这个表面
。

Bitmap Loading
位图载入

To load .bmp files we will use the standard Windows graphics library (GDI). This is best because if we're in a mode with a palette then Windows will automatically re-map the bitmap colours to the nearest in the palette. Here is the code that blits a loaded bitmap to a surface…. 
要载入.BMP图形文件，我们将使用标准的Windows图形库(GDI)。这个是最好的方法，因为如果我们是
在一个调色板的视频模式，那么Windows将自动将位图映射到最接近的调色板颜色。以下的代码是绘
制一个位图数据到表面……

Listing 2
代码列表 2

void DrawHBitmap(IDirectDrawSurface7 *lpSurface, HBITMAP hBitmap, int x, int y, int width, int height)
{
    HDC hdcImage;
    HDC hdc;
    BITMAP bm;

    if (lpSurface == NULL || hBitmap == NULL)
        return;
    lpSurface->Restore();

    hdcImage = CreateCompatibleDC(NULL);
    SelectObject(hdcImage, hBitmap);

    GetObject(hBitmap, sizeof(bm), &bm);
    width = width == 0 ? bm.bmWidth : width;
    height = height == 0 ? bm.bmHeight : height;

    lpSurface->GetDC(&hdc);
    BitBlt(hdc, x, y, width, height, hdcImage, 0, 0, SRCCOPY);
    lpSurface->ReleaseDC(hdc);
    DeleteDC(hdcImage);
}


and here is the code that loads, blits, then unloads the bitmap: 
以下的代码是把位图载入、绘制、到数据释放：

Listing 3
代码列表 3

void CreateBitmapSurface(LPDIRECTDRAWSURFACE7 lpSurface, char *fname, int xs, int ys)
{
    HBITMAP hBitmap;

    CreateSurface(&lpSurface, xs, ys);
    hBitmap = LoadImage(NULL, fname, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
    DrawHBitmap(lpSurface, hBitmap, 0, 0, xs, ys);
    DeleteObject(hBitmap);
}


Quick Example
快速例程

And to round it all up, here's some example code that loads the file "test.bmp" (width = 128, height = 128) into the lpddsTest surface, and then releases it again: 
围绕着以下部分，我们将结束此章节，这里是一些例程代码，它载入"test.bmp"文件(宽=128，高=12
8)到lpddTest表面中，并且将其释放：

Listing 4
代码列表 4

void Example(void)
{
/*
* Declare the surface object
* 声名表面对象
*/
    LPDIRECTDRAWSURFACE7 lpddsTest;

/*
* Load the bitmap file into it
* 载入位图文件
*/
    CreateBitmapSurface(lpddsTest, “test.bmp”, 128, 128);

/*
* The lpddsTest surface now contains the “test.bmp” file
* lpddsTest表面已经包含了"test.bmp"文件数据
*/

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