Loading Bitmap Files into DirectDraw
by Kieren Johnstone


Hi there.

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.

DirectDraw Surface Creation

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.

Listing 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.

Bitmap Loading

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….

Listing 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:

Listing 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

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:

Listing 4
void Example(void) { /* * Declare the surface object */ LPDIRECTDRAWSURFACE7 lpddsTest; /* * Load the bitmap file into it */ CreateBitmapSurface(lpddsTest, “test.bmp”, 128, 128); /* * The lpddsTest surface now contains the “test.bmp” file */ /* * Release the surface */ lpddsTest->Release(); }

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Date this article was posted to GameDev.net: 6/22/2000
(Note that this date does not necessarily correspond to the date the article was written)

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