grfmt_bmp.cpp

OPENCV系列的

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#include "stdwin.h"

#include "grfmt_bmp.h"
#include <assert.h>
#include <string.h>

static const char fmtDescrBmp[] = "Windows bitmap (*.bmp;*.dib)";
static const char fmtSignBmp[] = "BM";

/************************ BMP reader *****************************/

GrFmtBmpReader::GrFmtBmpReader()
{
    m_sign_len = 2;
    m_signature =fmtSignBmp;
    m_description = fmtDescrBmp;
    m_offset = -1;
}


GrFmtBmpReader::~GrFmtBmpReader()
{
    Close();
}

void  GrFmtBmpReader::Close()
{
    m_strm.Close();
}


bool  GrFmtBmpReader::ReadHeader()
{
    bool result = false;
    
    assert( strlen(m_filename) != 0 );
    if( !m_strm.Open( m_filename )) return false;

    try
    {
        m_strm.Skip( 10 );
        m_offset = m_strm.GetDWord();

        int  size = m_strm.GetDWord();

        if( size >= 36 )
        {
            m_width  = m_strm.GetDWord();
            m_height = m_strm.GetDWord();
            m_bpp    = m_strm.GetDWord() >> 16;
            m_rle_code = (BmpCompression)m_strm.GetDWord();
            m_strm.Skip(12);
            int clrused = m_strm.GetDWord();
            m_strm.Skip( size - 36 );

            if( m_width > 0 && m_height > 0 &&
             (((m_bpp == 1 || m_bpp == 4 || m_bpp == 8 || 
                m_bpp == 24 || m_bpp == 32 ) && m_rle_code == BMP_RGB) || 
               (m_bpp == 4 && m_rle_code == BMP_RLE4) ||
               (m_bpp == 8 && m_rle_code == BMP_RLE8))) 
            {
                m_iscolor = true;
                
                if( m_bpp <= 8 )
                {
                    memset( m_palette, 0, sizeof(m_palette));
                    m_strm.GetBytes( m_palette, (clrused == 0? 1<<m_bpp : clrused)*4 );
                    m_iscolor = IsColorPalette( m_palette, m_bpp );
                }
                result = true;
            }
        }
        else if( size == 12 )
        {
            m_width  = m_strm.GetWord();
            m_height = m_strm.GetWord();
            m_bpp    = m_strm.GetDWord() >> 16;
            m_rle_code = BMP_RGB;

            if( m_width > 0 && m_height > 0 &&
               (m_bpp == 1 || m_bpp == 4 || m_bpp == 8 ||
                m_bpp == 24 || m_bpp == 32 )) 
            {
                if( m_bpp <= 8 )
                {
                    uchar buffer[256*3];
                    int j, clrused = 1 << m_bpp;
                    m_strm.GetBytes( buffer, clrused*3 );
                    for( j = 0; j < clrused; j++ )
                    {
                        m_palette[j].b = buffer[3*j+0];
                        m_palette[j].g = buffer[3*j+1];
                        m_palette[j].r = buffer[3*j+2];
                    }
                }
                result = true;
            }
        }
    }
    catch( int )
    {
    }

    if( !result )
    {
        m_offset = -1;
        m_width = m_height = -1;
        m_strm.Close();
    }
    return result;
}


bool  GrFmtBmpReader::ReadData( uchar* data, int step, int color )
{
    const  int buffer_size = 1 << 12;
    uchar  buffer[buffer_size];
    uchar  bgr_buffer[buffer_size];
    uchar  gray_palette[256];
    bool   result = false;
    uchar* src = buffer;
    uchar* bgr = bgr_buffer;
    int  src_pitch = ((m_width*m_bpp + 7)/8 + 3) & -4;
    int  nch = color ? 3 : 1;
    int  width3 = m_width*nch;
    int  y;

    if( m_offset < 0 || !m_strm.IsOpened())
        return false;
    
    data += (m_height - 1)*step;
    step = -step;

    if( (m_bpp != 24 || !color) && src_pitch+32 > buffer_size )
        src = new uchar[src_pitch+32];

    if( !color )
    {
        if( m_bpp <= 8 )
        {
            CvtPaletteToGray( m_palette, gray_palette, 1 << m_bpp );
        }
        if( m_width*3 + 32 > buffer_size ) bgr = new uchar[m_width*3 + 32];
    }
    
    try
    {
        m_strm.SetPos( m_offset );
        
        switch( m_bpp )
        {
        /************************* 1 BPP ************************/
        case 1:
            for( y = 0; y < m_height; y++, data += step )
            {
                m_strm.GetBytes( src, src_pitch );
                FillColorRow1( color ? data : bgr, src, m_width, m_palette );
                if( !color ) CvtBGRToGray( bgr, data, m_width );
            }
            result = true;
            break;
        
        /************************* 4 BPP ************************/
        case 4:
            if( m_rle_code == BMP_RGB )
            {
                for( y = 0; y < m_height; y++, data += step )
                {
                    m_strm.GetBytes( src, src_pitch );
                    if( color )
                        FillColorRow4( data, src, m_width, m_palette );
                    else
                        FillGrayRow4( data, src, m_width, gray_palette );
                }
                result = true;
            }
            else if( m_rle_code == BMP_RLE4 ) // rle4 compression
            {
                uchar* line_end = data + width3;
                y = 0;

                for(;;)
                {
                    int code = m_strm.GetWord();
                    int len = code & 255;
                    code >>= 8;
                    if( len != 0 ) // encoded mode
                    {
                        PaletteEntry clr[2];
                        uchar gray_clr[2];
                        int t = 0;
                        
                        clr[0] = m_palette[code >> 4];
                        clr[1] = m_palette[code & 15];
                        gray_clr[0] = gray_palette[code >> 4];
                        gray_clr[1] = gray_palette[code & 15];

                        uchar* end = data + len*nch;
                        if( end > line_end ) goto decode_rle4_bad;
                        do
                        {
                            if( color )
                                WRITE_PIX( data, clr[t] );
                            else
                                *data = gray_clr[t];
                            t ^= 1;
                        }
                        while( (data += nch) < end );
                    }