hdr.cpp

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/* This file is part of the KDE project
   Copyright (C) 2005 Christoph Hormann <chris_hormann@gmx.de>
   Copyright (C) 2005 Ignacio Castaño <castanyo@yahoo.es>

   This program is free software; you can redistribute it and/or
   modify it under the terms of the Lesser GNU General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
*/

#include "hdr.h"

#include <QtGui/QImage>
#include <QtCore/QDataStream>

#include <kdebug.h>

typedef Q_UINT8 uchar;

namespace { // Private.

#define MAXLINE     1024
#define MINELEN     8       // minimum scanline length for encoding
#define MAXELEN     0x7fff  // maximum scanline length for encoding

    static inline uchar ClipToByte(float value)
    {
        if (value > 255.0f) return 255;
        //else if (value < 0.0f) return 0;  // we know value is positive.
        return uchar(value);
    }

    // read an old style line from the hdr image file
    // if 'first' is true the first byte is already read
    static bool Read_Old_Line (uchar * image, int width, QDataStream & s)
    {
        int  rshift = 0;
        int  i;

        while (width > 0)
        {
            s >> image[0];
            s >> image[1];
            s >> image[2];
            s >> image[3];

            if (s.atEnd()) return false;

            if ((image[0] == 1) && (image[1] == 1) && (image[2] == 1))
            {
                for (i = image[3] << rshift; i > 0; i--)
                {
                    //memcpy(image, image-4, 4);
                    (uint &)image[0] = (uint &)image[0-4];
                    image += 4;
                    width--;
                }
                rshift += 8;
            }
            else
            {
                image += 4;
                width--;
                rshift = 0;
            }
        }
        return true;
    }


    static void RGBE_To_QRgbLine(uchar * image, QRgb * scanline, int width)
    {
        for (int j = 0; j < width; j++)
        {
            // v = ldexp(1.0, int(image[3]) - 128);
            float v;
            int e = int(image[3]) - 128;
            if( e > 0 ) 
            {
                v = float(1 << e);
            }
            else 
            {
                v = 1.0f / float(1 << -e);
            }
            
            scanline[j] = qRgb( ClipToByte(float(image[0]) * v),
                                ClipToByte(float(image[1]) * v),
                                ClipToByte(float(image[2]) * v) );

            image += 4;
        }
    }

    // Load the HDR image.
    static bool LoadHDR( QDataStream & s, const int width, const int height, QImage & img )
    {
        uchar val, code;

        // Create dst image.
        if( !img.create( width, height, 32 ) )
        {
            return false;
        }

        QMemArray<uchar> image( width * 4 );
    
        for (int cline = 0; cline < height; cline++)
        {
            QRgb * scanline = (QRgb *) img.scanLine( cline );

            // determine scanline type
            if ((width < MINELEN) || (MAXELEN < width))
            {
                Read_Old_Line(image.data(), width, s);
                RGBE_To_QRgbLine(image.data(), scanline, width);
                continue;
            }

            s >> val;

            if (s.atEnd()) 
            {
                return true;
            }

            if (val != 2)
            {
                s.device()->at( s.device()->at() - 1 );
                Read_Old_Line(image.data(), width, s);
                RGBE_To_QRgbLine(image.data(), scanline, width);
                continue;
            }

            s >> image[1];
            s >> image[2];
            s >> image[3];

            if (s.atEnd()) 
            {
                return true;
            }

            if ((image[1] != 2) || (image[2] & 128))
            {
                image[0] = 2;
                Read_Old_Line(image.data()+4, width-1, s);
                RGBE_To_QRgbLine(image.data(), scanline, width);
                continue;
            }

            if ((image[2] << 8 | image[3]) != width)
            {
                return false;
            }

            // read each component
            for (int i = 0; i < 4; i++)
            {
                for (int j = 0; j < width; )
                {
                    s >> code;
                    if (s.atEnd())
                    {
                        return false;
                    }
                    if (code > 128)
                    {
                        // run
                        code &= 127;
                        s >> val;
                        while( code != 0 )
                        {
                            image[i + j * 4] = val;
                            j++;
                            code--;
                        }
                    }
                    else
                    {
                        // non-run
                        while( code != 0 )
                        {
                            s >> image[i +  j * 4];
                            j++;
                            code--;
                        }
                    }
                }
            }

            RGBE_To_QRgbLine(image.data(), scanline, width);
        }

        return true;
    }
        
} // namespace


KDE_EXPORT void kimgio_hdr_read( QImageIO * io )
{
    int len;
    char line[MAXLINE];
    //bool validHeader = false;
    bool validFormat = false;
    
    // Parse header 
    do {
        len = io->ioDevice()->readLine(line, MAXLINE);
    
        /*if (strcmp(line, "#?RADIANCE\n") == 0 || strcmp(line, "#?RGBE\n") == 0)
        {
            validHeader = true;
        }*/
        if (strcmp(line, "FORMAT=32-bit_rle_rgbe\n") == 0)
        {
            validFormat = true;
        }
        
    } while((len > 0) && (line[0] != '\n'));
    
    if(  !validFormat )
    {
        kDebug(399) << "Unknown HDR format.";
        io->setImage( 0 );
        io->setStatus( -1 );
        return;
    }
    
    io->ioDevice()->readLine(line, MAXLINE);    
    
    char s1[3], s2[3];
    int width, height;
    if (sscanf(line, "%2[+-XY] %d %2[+-XY] %d\n", s1, &height, s2, &width) != 4)
    //if( sscanf(line, "-Y %d +X %d", &height, &width) < 2 )
    {
        kDebug(399) << "Invalid HDR file.";
        io->setImage( 0 );
        io->setStatus( -1 );
        return;
    }
    
    QDataStream s( io->ioDevice() );

    QImage img;
    if( !LoadHDR(s, width, height, img) ) 
    {
        kDebug(399) << "Error loading HDR file.";
        io->setImage( 0 );
        io->setStatus( -1 );
        return;
    }

    io->setImage( img );
    io->setStatus( 0 );
}


KDE_EXPORT void kimgio_hdr_write( QImageIO * )
{
    // intentionally not implemented (since writing low dynamic range data to a HDR file is nonsense.)
}