"This," being a test I did some time ago. I quickly
documented it and made sure it compiled, but other
than for loading a test PNG, I haven't tested it
further.

The code's pretty ugly in parts. Basically what
it does is load a PNG and make a DIB out of it with
MakeDIB(). Then, with MakeCompatibleSurface(), it
creates a DirectDraw surface and BitBlt()s that
DIB onto it.

A quick example of using it:

code:

MyPNG png;// I'll just pretend my code is// perfect and there's no need// for error processing.png.MakeDIB( "paddle.png" );// Oh no!  Global variables!png.MakeCompatibleSurface( g_lpDD, &g_lpPaddleSprite );png.DoCleanUp();png.MakeDIB( "ball.png" );png.MakeCompatibleSurface( g_lpDD,&g_lpBallSprite );PlayPong();

Using this, you don't have to worry about pixel format
conversion but, as I said, it might be better to
do that anyway. Try searching for information
on plotting 16bpp pixels in DirectDraw.

Note: this assumes you have libpng and zlib
already, so make sure you link to them.

code:

#ifndef __MY_PNG_INCLUDED__#define __MY_PNG_INCLUDED__#define WIN32_LEAN_AND_MEAN#include #include #include LIBPNG_HEADER_LOCATION// Number of bytes read by IsPNG() to// check for the file's signature.#define MYPNG_BYTES_TO_CHECK						4// The following specifies the RGB colours of the default// background.  The class doesn't preserve alpha// values.  Instead it tries to combine them with// the image's background or, if none is provided,// creates a default background from these// #defines.  If you define MYPNG_STRIP_ALPHA,// the alpha values are stripped instead of// combined.#undef MYPNG_STRIP_ALPHA/* Specifies a black background. */#define MYPNG_DEFAULT_BACKGROUND_RED			0#define MYPNG_DEFAULT_BACKGROUND_GREEN			0#define MYPNG_DEFAULT_BACKGROUND_BLUE			0enum MYPNG_STATUS{	MYPNG_OK,	MYPNGERR_FILECOULDNTBEACCESSED,	MYPNGERR_NOTAPNG,	MYPNGERR_NOTENOUGHMEMORY,	MYPNGERR_DIBNOTCREATED,	MYPNGERR_COULDNTCREATESURFACE,	MYPNGERR_COULDNTGETSRCCONTEXT,	MYPNGERR_COULDNTGETDESTCONTEXT,	MYPNGERR_COULDNTBLIT};class MyPNG{   public:      MyPNG();      ~MyPNG();		// Clears and resets all variables.		void DoCleanUp();      // Open a PNG file specified by 'filename', extract data      // from it and convert it into a device-independent      // bitmap.  Returns: MYPNG_OK on success, or a		// MYPNGERR_something.            MYPNG_STATUS MakeDIB( LPCSTR filename );            // Create an off-screen DirectDraw surface and BitBlt()      // the DIB onto it.  It takes as arguments a pointer      // to a DirectDraw object and a pointer to a DirectDraw      // surface pointer.  Returns: MYPNG_OK on success,		// else a MYPNGERR_something.            MYPNG_STATUS MakeCompatibleSurface( LPDIRECTDRAW4 lpdd, LPDIRECTDRAWSURFACE4         *surface );            private:      /*    Private function declarations.    */		BOOL IsPNG();				// Determines if the open										// file is a PNG.      void Initialize();      // Resets all variables.                  MYPNG_STATUS OpenFile( LPCSTR file ); // Opens a file and														  // extracts information														  // to the PNG structs.		BOOL ConvertToDIB();		// Sets up a DIB and writes										// image data into it.				BOOL CloseFile();       // Closes an open file and destroys                              // created PNG structs.            /*    Private variable declarations.    */            FILE       *m_pFile;    // Currently open file.      HBITMAP     m_hbm;      // Handle to a generated DIB.      png_structp m_pStruct;  // Currently open PNG file struct.      png_infop   m_pInfo;    // Currently open PNG info struct.      png_uint_32 m_Width;    // Width of image.      png_uint_32 m_Height;   // Height of image.};#endif#include "mypng.h"MyPNG::MyPNG(){	Initialize();} /* MyPNG() */MyPNG::~MyPNG(){	DoCleanUp();} /* MyPNG() */void MyPNG::Initialize(){	m_Width		= 0;	m_Height		= 0;	m_hbm			= NULL;	m_pFile		= NULL;	m_pInfo		= NULL;	m_pStruct	= NULL;} /* Initialize() */BOOL MyPNG::CloseFile(){			if( m_pStruct != NULL | | m_pInfo != NULL )	{		// Destroy created PNG structs.		png_destroy_read_struct( &m_pStruct, &m_pInfo, NULL );		m_pStruct = NULL;		m_pInfo = NULL;	}	if( m_pFile != NULL )	{		// Close open file.		fclose( m_pFile );		m_pFile = NULL;	}	else	{		return FALSE;	}	return TRUE;} /* CloseFile() */void MyPNG:    oCleanUp(){	CloseFile();			if( m_hbm )	{		// Does deleting an object also free the memory		// allocated to the bitmap pointer?  If not, this		// causes a serious memory leak because I'm too		// lazy to check it out and free it myself. :P		DeleteObject( m_hbm );		m_hbm = NULL;	}	Initialize();} /* DoCleanUp() */BOOL MyPNG::IsPNG(){	unsigned char buf[ MYPNG_BYTES_TO_CHECK ];	if( m_pFile == NULL )	{		// No file currently open.		return FALSE;	}	if( fread( buf, sizeof( unsigned char ), MYPNG_BYTES_TO_CHECK,		m_pFile ) != MYPNG_BYTES_TO_CHECK )	{		return FALSE;	}	if( png_sig_cmp( buf, ( png_size_t )0, MYPNG_BYTES_TO_CHECK ) == 1 )	{		// File signature match failed.  Not a PNG file.		return FALSE;	}	return TRUE;} /* IsPNG */MYPNG_STATUS MyPNG::MakeDIB( LPCSTR filename ){	MYPNG_STATUS retval;	// First open the file and extract header data.	retval = OpenFile( filename );	if( retval != MYPNG_OK )	{		DoCleanUp();		return retval;	}	if( !ConvertToDIB() )	{		DoCleanUp();		return MYPNGERR_NOTENOUGHMEMORY;	}	// The DIB can now be blitted onto a compatible	// surface.	return MYPNG_OK;} /* MakeDIB() */MYPNG_STATUS MyPNG::OpenFile( LPCSTR filename ){		/* Note that this is largely a copy of the		example file included in libpng. */#ifndef MYPNG_STRIP_ALPHA	png_color_16 my_background, *image_background;#endif	if( m_pFile != NULL | | m_hbm != NULL )	{		// File's already loaded.		DoCleanUp();		Initialize();	}	// Open the proposed file for reading.	m_pFile = fopen( filename, "rb" );	if( m_pFile == NULL )	{		// Couldn't access the file.		return MYPNGERR_FILECOULDNTBEACCESSED;	}	// Check if the file's a PNG file.	if( !this->IsPNG() )	{		return MYPNGERR_NOTAPNG;	}   // Create the PNG stuctures.	m_pStruct = png_create_read_struct( PNG_LIBPNG_VER_STRING,		NULL, NULL, NULL );	if ( m_pStruct == NULL )	{		// Oh dear.		return MYPNGERR_NOTENOUGHMEMORY;	}	m_pInfo = png_create_info_struct( m_pStruct );	if( m_pInfo == NULL )	{		// Oh dear oh dear.		return MYPNGERR_NOTENOUGHMEMORY;	}	// Used for default error handling.  Er, I think. :-/	if( setjmp( m_pStruct->jmpbuf ) )	{		return MYPNGERR_NOTENOUGHMEMORY;	}	// We've read some of the signature bytes, so let's let them	// know.	png_set_sig_bytes( m_pStruct, MYPNG_BYTES_TO_CHECK );	// Initialize default I/O routines.	png_init_io( m_pStruct, m_pFile );	// Read information into the info structure.	png_read_info( m_pStruct, m_pInfo );	// Strip 16 bit/channel files down to 8 bits/channel.	png_set_strip_16( m_pStruct );	// Expand palette and grayscale information to RGB triplets.	switch( m_pInfo->color_type )	{	case PNG_COLOR_TYPE_PALETTE:	case PNG_COLOR_TYPE_GRAY:		png_set_expand( m_pStruct );		break;	}	// Expand packed colour information to their own	// bytes.	switch( m_pInfo->bit_depth )	{	case 1:	case 2:	case 4:		png_set_packing( m_pStruct );		break;	}	// Swap the R and B bits.  This is required for Windows DIBs.	png_set_bgr( m_pStruct );	if( png_get_valid( m_pStruct, m_pInfo, PNG_INFO_tRNS ) )	{		png_set_expand( m_pStruct );	}#ifdef MYPNG_STRIP_ALPHA	// Strip alpha values (not recommended).	png_set_strip_alpha( png_ptr );#else	// Combine alpha values with the background.	if( png_get_bKGD( m_pStruct, m_pInfo, ℑ_background ) )	{		// Image had its own background.		png_set_background( m_pStruct, image_background,			PNG_BACKGROUND_GAMMA_FILE, 1, 1.0 );	}	else	{		// No background provided.  We'll make one.		my_background.red = MYPNG_DEFAULT_BACKGROUND_RED;		my_background.blue = MYPNG_DEFAULT_BACKGROUND_BLUE;		my_background.green = MYPNG_DEFAULT_BACKGROUND_GREEN;		png_set_background( m_pStruct, &my_background,			PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0 );	}#endif	// Finally update the info struct.	png_read_update_info( m_pStruct, m_pInfo );	return MYPNG_OK;} /* OpenFile() */BOOL MyPNG::ConvertToDIB(){	// PNG image's scanline length in bytes.	png_uint_32 rowsize;	// The future DIB's scanline length.  DIBs are	// LONG-aligned with the unused bytes set to 0.	png_uint_32 realrowsize;	// Counter.	png_uint_32 row;	BITMAPINFOHEADER bmih;	// Pointer returned by CreateDIBSection() where	// we can write our data.	png_bytep OurDIB;	if( m_pStruct == NULL | | m_pInfo == NULL | | m_pFile == NULL )	{		// No file open. :-/		return FALSE;	}	// Get the scanline length.	rowsize = png_get_rowbytes( m_pStruct, m_pInfo );	realrowsize = rowsize + ( rowsize % sizeof( LONG ) );	// Fill in the BITMAPINFOHEADER	ZeroMemory( &bmih, sizeof( bmih ) );	bmih.biSize				 = sizeof( bmih );	bmih.biWidth			 = m_pInfo->width;	// DIB only displays top->down if the height is negative.	bmih.biHeight			 = -( int )m_pInfo->height;	bmih.biPlanes			 = 1;	bmih.biBitCount		 = m_pInfo->bit_depth * m_pInfo->channels;	bmih.biCompression	 = BI_RGB;	bmih.biSizeImage		 = 0;	bmih.biXPelsPerMeter  = 0;	bmih.biYPelsPerMeter  = 0;	bmih.biClrUsed        = 0;	bmih.biClrImportant   = 0;	// Create a DIB we can write to from the info in the header.	m_hbm = CreateDIBSection( NULL, ( BITMAPINFO * )&bmih, DIB_RGB_COLORS,		( void ** )&OurDIB, NULL, 0 );	if ( m_hbm == NULL )	{		// Well we screwed up somewhere.		return FALSE;	}	// Initialize the bitmap with zeros.  Yeah, I did this	// just because unused bytes are set to zero,	// and this is a HIDEOUS way to do it.  I just don't	// feel like rewriting it for the sake of this post.     	ZeroMemory( OurDIB, m_pInfo->height * realrowsize );	m_Width = m_pInfo->width;	m_Height = m_pInfo->height;	// Read (write) one row at a time.	for( row = 0; row < m_pInfo->height; row ++ )	{		png_read_rows( m_pStruct, &OurDIB, NULL, 1 );		OurDIB += realrowsize;	}	// Finish reading.	png_read_end( m_pStruct, m_pInfo );	return TRUE;} /* MakeDIB() */MYPNG_STATUS MyPNG::MakeCompatibleSurface( LPDIRECTDRAW4 lp_dd, LPDIRECTDRAWSURFACE4 *lp_surface ){	HRESULT retval;	HDC hdc_src, hdc_dest;	DDSURFACEDESC2 ddsd;	LPDIRECTDRAWSURFACE4 surf;	if( m_hbm == NULL )	{		// Oops!  No DIB to create from.		return MYPNGERR_DIBNOTCREATED;	}	// Set up the surface parameters.	ZeroMemory( &ddsd, sizeof( ddsd ) );	ddsd.dwSize = sizeof( ddsd );	ddsd.dwFlags = DDSD_WIDTH | DDSD_HEIGHT | DDSD_CAPS;	ddsd.dwWidth = m_Width;	ddsd.dwHeight = m_Height;	ddsd.ddsCaps.dwCaps = DDSCAPS_OFFSCREENPLAIN;	retval = lp_dd->CreateSurface( &ddsd, &surf, NULL );	if( FAILED( retval ) )	{		return MYPNGERR_COULDNTCREATESURFACE;	}	// Create a device context to blit from.	hdc_src = CreateCompatibleDC( NULL );	if( !hdc_src ) 	{		surf->Release();		surf = NULL;		return MYPNGERR_COULDNTGETSRCCONTEXT;	}	SelectObject( hdc_src, m_hbm );	// Get the context to blit onto.	surf->GetDC( &hdc_dest );	if( !hdc_dest )	{		DeleteDC( hdc_src );		surf->Release();		surf = NULL;		return MYPNGERR_COULDNTGETDESTCONTEXT;	}	if( !BitBlt( hdc_dest, 0, 0, m_Width, m_Height,						  hdc_src, 0, 0, SRCCOPY ) )	{		DeleteDC( hdc_src );		surf->ReleaseDC( hdc_dest );		surf->Release();		surf = NULL;		return MYPNGERR_COULDNTBLIT;	}	DeleteDC( hdc_src );	surf->ReleaseDC( hdc_dest );	*lp_surface = surf;	return MYPNG_OK;} /* MakeCompatibleSurface() */

[This message has been edited by foo (edited August 08, 1999).]

[This message has been edited by foo (edited August 08, 1999).]

[This message has been edited by foo (edited August 08, 1999).]