HOWTO: How To Use LoadImage() to Read a BMP File

Summary

The LoadImage API can be used to load a bitmap from a BMP file. However, it does not return palette information. This article provides sample code and describes how to retrieve the palette information for the bitmap with LoadImage.

More Information

The following code uses the LoadImage API to load the bitmap as a DIBSection, and then creates a palette from the DIBSection's color table. If no color table is present, a halftone palette is used:

   BOOL LoadBitmapFromBMPFile( LPTSTR szFileName, HBITMAP *phBitmap,
HPALETTE *phPalette )
{

BITMAP bm;

*phBitmap = NULL;
*phPalette = NULL;

// Use LoadImage() to get the image loaded into a DIBSection
*phBitmap = (HBITMAP)LoadImage( NULL, szFileName, IMAGE_BITMAP, 0, 0,
LR_CREATEDIBSECTION | LR_DEFAULTSIZE | LR_LOADFROMFILE );
if( *phBitmap == NULL )
return FALSE;

// Get the color depth of the DIBSection
GetObject(*phBitmap, sizeof(BITMAP), &bm );
// If the DIBSection is 256 color or less, it has a color table
if( ( bm.bmBitsPixel * bm.bmPlanes ) <= 8 )
{
HDC hMemDC;
HBITMAP hOldBitmap;
RGBQUAD rgb[256];
LPLOGPALETTE pLogPal;
WORD i;

// Create a memory DC and select the DIBSection into it
hMemDC = CreateCompatibleDC( NULL );
hOldBitmap = (HBITMAP)SelectObject( hMemDC, *phBitmap );
// Get the DIBSection's color table
GetDIBColorTable( hMemDC, 0, 256, rgb );
// Create a palette from the color tabl
pLogPal = (LOGPALETTE *)malloc( sizeof(LOGPALETTE) + (256*sizeof(PALETTEENTRY)) );
pLogPal->palVersion = 0x300;
pLogPal->palNumEntries = 256;
for(i=0;i<256;i++)
{
pLogPal->palPalEntry[i].peRed = rgb[i].rgbRed;
pLogPal->palPalEntry[i].peGreen = rgb[i].rgbGreen;
pLogPal->palPalEntry[i].peBlue = rgb[i].rgbBlue;
pLogPal->palPalEntry[i].peFlags = 0;
}
*phPalette = CreatePalette( pLogPal );
// Clean up
free( pLogPal );
SelectObject( hMemDC, hOldBitmap );
DeleteDC( hMemDC );
}
else // It has no color table, so use a halftone palette
{
HDC hRefDC;

hRefDC = GetDC( NULL );
*phPalette = CreateHalftonePalette( hRefDC );
ReleaseDC( NULL, hRefDC );
}
return TRUE;

}
The following code demonstrates how to use the LoadBitmapFromBMPFilefunction:

   case WM_PAINT:
{
PAINTSTRUCT ps;
HBITMAP hBitmap, hOldBitmap;
HPALETTE hPalette, hOldPalette;
HDC hDC, hMemDC;
BITMAP bm;

hDC = BeginPaint( hWnd, &ps );

if( LoadBitmapFromBMPFile( szFileName, &hBitmap, &hPalette ) )
{
GetObject( hBitmap, sizeof(BITMAP), &bm );
hMemDC = CreateCompatibleDC( hDC );
hOldBitmap = (HBITMAP)SelectObject( hMemDC, hBitmap );
hOldPalette = SelectPalette( hDC, hPalette, FALSE );
RealizePalette( hDC );

BitBlt( hDC, 0, 0, bm.bmWidth, bm.bmHeight,
hMemDC, 0, 0, SRCCOPY );

SelectObject( hMemDC, hOldBitmap );
DeleteObject( hBitmap );
SelectPalette( hDC, hOldPalette, FALSE );
DeleteObject( hPalette );
}
EndPaint( hWnd, &amp;ps );

}
break;
คุณสมบัติ

รหัสบทความ: 158898 - การตรวจสอบครั้งสุดท้าย: 21 พ.ย. 2006 - ฉบับแก้ไข: 1

คำติชม