Loading Bitmap Files into DirectDraw

Describes how to use Windows functions to load a bitmap to a DirectDraw surface.

June 22, 2000 10.1k views

[size="5"]Introduction

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.

[size="5"]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.

[size="5"]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);
 }

[size="5"]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();
 }

Loading Bitmap Files into DirectDraw

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