bmp.cpp

/*------------------------------------------------------------------
 BMP Loader - a quick and dirty substitute for GLaux
 if you only use GLaux to load BMP files will load any format of a
 windows DIB BMP format graphics file Only works on a windows box
 Caution! memory for the data is allocated using 'new'.
 In the NeHe tutorials the memory is reclaimed using 'free'.
 For the small tutorials its not a big deal but not a good practice in
 larger projects (heap trashing not good). J.M. Doyle : 12 Jan 2003
------------------------------------------------------------------*/
#include "precompiled.h"

AUX_RGBImageRec *auxDIBImageLoad( const char *FileName )
{
	return new AUX_RGBImageRec( FileName );
}


void AUX_RGBImageRec::convertBGRtoRGB()
{
	const DWORD BitmapLength = sizeX * sizeY * 3;
	byte Temp;  // not quick but it works
	for( DWORD i = 0; i < BitmapLength; i += 3 ) {
		Temp = data[i];
		data[i] = data[i+2];
		data[i+2] = Temp;
	}
}

AUX_RGBImageRec::AUX_RGBImageRec( const char *FileName ): data( NULL ), NoErrors( false )
{
	loadFile( FileName );
}

AUX_RGBImageRec::~AUX_RGBImageRec()
{
	if( data != NULL ) delete data;
	data = NULL;
}

bool AUX_RGBImageRec::loadFile( const char* Filename )
{
	BITMAPINFO BMInfo;                                                              // need the current OpenGL device contexts in order to make use of windows DIB utilities
	const HDC gldc = wglGetCurrentDC();                     // a handle for the current OpenGL Device Contexts
	// assume there are errors until file is loaded successfully into memory
	NoErrors = false;                                                               // release old data since this object could be used to load multiple Textures
	if( data != NULL ) delete data;                                 // windows needs this info to determine what header info we are looking for
	BMInfo.bmiHeader.biSize = sizeof( BITMAPINFOHEADER ); // Get windows to determine color bit depth in the file for us
	BMInfo.bmiHeader.biBitCount = 0;                                // Get windows to open and load the BMP file and handle the messy decompression if the file is compressed
	// assume perfect world and no errors in reading file, Ha Ha
	HANDLE DIBHandle = LoadImage( 0, Filename, IMAGE_BITMAP, 0, 0, LR_DEFAULTCOLOR | LR_CREATEDIBSECTION | LR_LOADFROMFILE ); // use windows to get header info of bitmap - assume no errors in header format
	
	GetDIBits( gldc, ( HBITMAP )DIBHandle, 0, 0, NULL, &BMInfo, DIB_RGB_COLORS );
	sizeX = BMInfo.bmiHeader.biWidth;
	sizeY = BMInfo.bmiHeader.biHeight;                              // change color depth to 24 bits (3 bytes (BGR) / pixel)
	BMInfo.bmiHeader.biBitCount = 24;                               // don't want the data compressed
	BMInfo.bmiHeader.biCompression = BI_RGB;
	const DWORD BitmapLength = sizeX * sizeY * 3;   // 3 bytes (BGR) per pixel (24bp)
	// allocate enough memory to hold the pixel data in client memory
	data = new byte[BitmapLength];                                  // Get windows to do the dirty work of converting the BMP into the format needed by OpenGL
	// if file is already 24 bit color then this is a waste of time but makes for short code
	// Get the actual Texel data from the BMP object
	
	if( GetDIBits( gldc, ( HBITMAP )DIBHandle, 0, sizeY, data, &BMInfo, DIB_RGB_COLORS ) ) {
		NoErrors = true;
		convertBGRtoRGB();                                                      // NOTE: BMP is in BGR format but OpenGL needs RGB unless you use GL_BGR_EXT
	}
	
	DeleteObject( DIBHandle );                                              // don't need the BMP Object anymore
	return NoErrors;
}