image.cpp

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/** @file
 *  @author Bram de Greve (bramz@users.sourceforge.net)
 *  @author Tom De Muer (tomdemuer@users.sourceforge.net)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2004-2007 the Initial Developer.
 *  All Rights Reserved.
 *  
 *  Contributor(s):
 *
 *  Alternatively, the contents of this file may be used under the terms of the 
 *  GNU General Public License Version 2 or later (the GPL), in which case the 
 *  provisions of GPL are applicable instead of those above.  If you wish to allow use
 *  of your version of this file only under the terms of the GPL and not to allow 
 *  others to use your version of this file under the CPAL, indicate your decision by 
 *  deleting the provisions above and replace them with the notice and other 
 *  provisions required by the GPL License. If you do not delete the provisions above,
 *  a recipient may use your version of this file under either the CPAL or the GPL.
 *  
 *  *** END LICENSE INFORMATION ***
 */

#include "io_common.h"
#include "image.h"
#include "binary_i_file.h"
#include "binary_o_file.h"
#include "file_attribute.h"
#include "../stde/extended_string.h"
#include "../stde/extended_algorithm.h"
#include "../stde/range_algorithm.h"
#include "../stde/static_vector.h"
#include "../prim/transformation_3d.h"

#define LASS_IO_IMAGE_ENFORCE_SAME_SIZE(a, b)\
    LASS_UTIL_IMPL_MAKE_ENFORCER(\
        ::lass::util::impl::TruePredicate,\
        ::lass::util::impl::DefaultRaiser,\
        ((a).rows() == (b).rows() && (a).cols() == (b).cols()),\
        int(0),\
        "Images '" LASS_STRINGIFY(a) "' and '" LASS_STRINGIFY(b) "' have different size in '" LASS_HERE "'.")

namespace lass
{
namespace io
{
namespace impl
{
    class Bytes4
    {
    public:
        const num::Tuint8 operator[](std::size_t k) const { LASS_ASSERT(k < 4); return values_[k]; }
        num::Tuint8& operator[](std::size_t k) { LASS_ASSERT(k < 4); return values_[k]; }
        const num::Tuint8* get() const { return values_; }
        num::Tuint8* get() { return values_; }
        bool operator==(const Bytes4& other) const { return std::equal(values_, values_ + 4, other.values_); }
    private:
        num::Tuint8 values_[4];
    };
}

Image::TFileFormats Image::fileFormats_ = Image::fillFileFormats();
num::Tuint32 Image::magicLass_ = 0x7373616c; // 'lass' in little endian
std::string Image::magicRadiance_ = "#?RADIANCE\n";
num::Tint32 Image::magicIgi_ = 66613373;

// --- public --------------------------------------------------------------------------------------

/** Default constructor.  empty image.
 */
Image::Image():
    colorSpace_(defaultColorSpace()),
    rows_(0),
    cols_(0),
    raster_()
{
}



/** Construct image of given width and height.
 */
Image::Image(unsigned rows, unsigned cols):
    colorSpace_(defaultColorSpace()),
    rows_(0),
    cols_(0),
    raster_()
{
    const TPixel black;
    resize(rows, cols);
    std::fill(raster_.begin(), raster_.end(), black);
}



/** Construct image from given file.
 */
Image::Image(const std::string& filename):
    colorSpace_(defaultColorSpace()),
    rows_(0),
    cols_(0),
    raster_()
{
    open(filename);
}



/** Copy constructor
 */
Image::Image(const Image& other):
    colorSpace_(other.colorSpace_),
    rows_(other.rows_),
    cols_(other.cols_),
    raster_(other.raster_)
{
}



/** Destructor
 */
Image::~Image()
{
}



// --- PUBLIC METHODS ----------------------------------------------------------

/** Reset image to empty image.
 */
void Image::reset()
{
    Image temp;
    swap(temp);
}



/** Reset image to (black) image of given width.
 */
void Image::reset(unsigned rows, unsigned cols)
{
    Image temp(rows, cols);
    swap(temp);
}



/** Reset image to the one in the given file.
 */
void Image::reset(const std::string& filename)
{
    Image temp(filename);
    swap(temp);
}



/** Reset image to copy of given image.
 */
void Image::reset(const Image& other)
{
    Image temp(other);
    swap(temp);
}



/** Open image from file
 */
void Image::open(const std::string& filename)
{
    try
    {
        BinaryIFile file(filename);
        if (!file)
        {
            LASS_THROW("could not open file to read.");
        }

        open(file, fileExtension(filename));
    }
    catch (const BadFormat& error)
    {
        LASS_THROW_EX(BadFormat, "'" << filename << "': " << error.message());
    }
    catch (const util::Exception& error)
    {
        LASS_THROW("'" << filename << "': " << error.message());
    }
}



/** Open image from binary stream
 */
void Image::open(BinaryIStream& stream, const std::string& formatTag)
{
    Image temp;
    TFileOpener opener = findFormat(formatTag).open;
    if (!opener)
    {
        LASS_THROW_EX(BadFormat, "cannot open images in file format '" << formatTag << "'.");
    }

    (temp.*opener)(stream);

    if (stream.good())
    {
        swap(temp);
    }
    else if (stream.eof())
    {
        LASS_THROW_EX(BadFormat, "tried to read past end of file.");
    }
    else
    {
        LASS_THROW_EX(BadFormat, "unknown failure in file.");
    }
}



/** Save image to file
 */
void Image::save(const std::string& filename)
{
    try
    {
        BinaryOFile file(filename);
        if (!file)
        {
            LASS_THROW("could not open file to write.");
        }

        save(file, fileExtension(filename));
    }
    catch (const BadFormat& error)
    {
        LASS_THROW_EX(BadFormat, "'" << filename << "': " << error.message());
    }
    catch (const util::Exception& error)
    {
        LASS_THROW_EX(BadFormat, "'" << filename << "': " << error.message());
    }
}



/** Save image to file
 */
void Image::save(BinaryOStream& stream, const std::string& formatTag)
{
    TFileSaver saver = findFormat(formatTag).save;
    if (!saver)
    {
        LASS_THROW_EX(BadFormat, "cannot save images in file format '" << formatTag << "'.");
    }

    (this->*saver)(stream);

    if (stream.eof())
    {
        LASS_THROW_EX(BadFormat, "tried to write past end of file.");
    }
    if (!stream.good())
    {
        LASS_THROW_EX(BadFormat, "unknown failure in file.");
    }
}



/** Copy other into this image.
 */
Image& Image::operator=(const Image& other)
{
    Image temp(other);
    swap(temp);
    return *this;
}



/** swap two images
 */
void Image::swap(Image& other)
{
    std::swap(colorSpace_, other.colorSpace_);
    std::swap(rows_, other.rows_);
    std::swap(cols_, other.cols_);
    raster_.swap(other.raster_);
}



/** Return const pixel at position row, col.
 *  @param row row of pixel, y coordinate.
 *  @param col column of pixel, x coordinate.
 */
const Image::TPixel& Image::operator()(unsigned row, unsigned col) const
{
    LASS_ASSERT(row < rows_ && col < cols_);
    return raster_[flatIndex(row, col)];
}



/** Return reference to pixel at position row, col.
 *  @param row row of pixel, y coordinate.
 *  @param col column of pixel, x coordinate.
 */
Image::TPixel& Image::operator()(unsigned row, unsigned col)
{
    LASS_ASSERT(row < rows_ && col < cols_);
    return raster_[flatIndex(row, col)];
}



/** Return const pixel at position row, col.  position is wrapped around.
 *  @param row row of pixel, y coordinate.
 *  @param col column of pixel, x coordinate.
 */
const Image::TPixel& Image::at(signed row, signed col) const
{
    const unsigned i = num::mod(row, rows_);
    const unsigned j = num::mod(col, cols_);
    return raster_[flatIndex(i, j)];
}



/** Return reference to pixel at position row, col. position is wrapped around.
 *  @param row row of pixel, y coordinate.
 *  @param col column of pixel, x coordinate.
 */
Image::TPixel& Image::at(signed row, signed col)
{
    const unsigned i = num::mod(row, rows_);
    const unsigned j = num::mod(col, cols_);
    return raster_[flatIndex(i, j)];
}



/** Return const data block.
 */
const Image::TPixel* const Image::data() const
{
    return &raster_[0];
}



/** Return data block.
 */
Image::TPixel* const Image::data()
{
    return &raster_[0];
}



/** Return colorSpace of image data
 */
const Image::ColorSpace& Image::colorSpace() const
{
    return colorSpace_;
}



/** Return colorSpace of image data
 *
 *  You can change the parameters of the current color space without transforming
 *  the pixels.  This is most useful if you know that the pixels are in a different
 *  color space that the current one is set to.  For example, if you know the pixels
 *  have a gamma correction 2.2 applied, but the this->colorSpace().gamma == 1.
 */
Image::ColorSpace& Image::colorSpace()
{
    return colorSpace_;
}



/** Transform the colors from the current color spacer to @a destColorSpace.
 *
 *  The transformation consists of three stages:
 *  @arg linearise pixels if gamma of current color space != 1
 *  @arg transform colors to linearised destination colour space
 *  @arg apply gamma correction if @a destColorSpace.gamma != 1
 *
 *  For the color transformation, two transformations are concatenated.
 *  Both of them will also perform a chromatic adaption transform if 
 *  the white point of either color space is not the equal energy one (E):
 *  @arg from source RGB to XYZ
 *  @arg from XYZ to dest RGB
 */
void Image::transformColors(const ColorSpace& newColorSpace)
{
    typedef prim::Transformation3D<TValue> TTransformation;

    struct Impl
    {
        static const TTransformation rgb2xyz(const ColorSpace& colorSpace)
        {
            typedef TTransformation::TVector TVector;
            const ColorSpace& C = colorSpace;
            TValue primaries[16] = 
            {
                C.red.x, C.green.x, C.blue.x, 0,
                C.red.y, C.green.y, C.blue.y, 0,
                1 - C.red.x - C.red.y, 1 - C.green.x - C.green.y, 1 - C.blue.x - C.blue.y, 0,
                0, 0, 0, 1
            };
            TTransformation M(primaries, primaries + 16);
            const TVector w(C.white.x / C.white.y, 1, (1 - C.white.x - C.white.y) / C.white.y);
            const TVector S = transform(w, M.inverse());
            M = concatenate(TTransformation::scaler(S), M);

            TValue bradford[16] = 
            {
                 0.8951f,  0.2664f, -0.1614f, 0.f,
                -0.7502f,  1.7135f,  0.0367f, 0.f,
                 0.0389f, -0.0685f,  1.0296f, 0.f,
                 0.f,      0.f,      0.f,     1.f
            };
            const TTransformation B(bradford, bradford + 16);
            const TVector sw = transform(w, B);
            TTransformation M_cat = concatenate(B, TTransformation::scaler(sw.reciprocal()));
            M_cat = concatenate(M_cat, B.inverse());
            
            return concatenate(M, M_cat);
        }
    };

    const TTransformation A = Impl::rgb2xyz(colorSpace_);
    const TTransformation B = Impl::rgb2xyz(newColorSpace);
    const TTransformation C = concatenate(A, B.inverse());

    if (colorSpace_.gamma != 1)
    {
        filterGamma(1 / colorSpace_.gamma);
    }
    for (TRaster::iterator i = raster_.begin(); i != raster_.end(); ++i)
    {
        *i = transform(*i, C);
    }
    if (newColorSpace.gamma != 1)
    {
        filterGamma(newColorSpace.gamma);
    }
    colorSpace_ = newColorSpace;
    colorSpace_.isFromFile = false;
}



/** Return height of image.
 */
const unsigned Image::rows() const
{
    return rows_;
}



/** Return width of image.
 */
const unsigned Image::cols() const
{
    return cols_;
}



/** Return true if image is empty (no data)
 */
const bool Image::isEmpty() const
{
    return raster_.empty();
}



/** this = this over other
 */
void Image::over(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(raster_.begin(), raster_.end(), other.raster_.begin(), raster_.begin(), prim::over);
}



/** this = this in other
 */
void Image::in(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(raster_.begin(), raster_.end(), other.raster_.begin(), raster_.begin(), prim::in);
}



/** this = this out other
 */
void Image::out(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(raster_.begin(), raster_.end(), other.raster_.begin(), raster_.begin(), prim::out);
}



/** this = this atop other
 */
void Image::atop(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(raster_.begin(), raster_.end(), other.raster_.begin(), raster_.begin(), prim::atop);
}



/** this = this through other
 */
void Image::through(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(raster_.begin(), raster_.end(), other.raster_.begin(), raster_.begin(), prim::through);
}



/** this = other over this
 */
void Image::rover(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(other.raster_.begin(), other.raster_.end(), raster_.begin(), raster_.begin(), prim::over);
}



/** this = other in this
 */
void Image::rin(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(other.raster_.begin(), other.raster_.end(), raster_.begin(), raster_.begin(), prim::in);
}



/** this = other out this
 */
void Image::rout(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(other.raster_.begin(), other.raster_.end(), raster_.begin(), raster_.begin(), prim::out);
}



/** this = other atop this
 */
void Image::ratop(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(other.raster_.begin(), other.raster_.end(), raster_.begin(), raster_.begin(), prim::atop);
}



/** this = other through this
 */
void Image::rthrough(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(other.raster_.begin(), other.raster_.end(), raster_.begin(), raster_.begin(), prim::through);
}



/** this = this plus other = other plus this
 */
void Image::plus(const Image& other)
{
    LASS_IO_IMAGE_ENFORCE_SAME_SIZE(*this, other);
    std::transform(raster_.begin(), raster_.end(), other.raster_.begin(), raster_.begin(), prim::plus);
}



/** clamp all negative pixel components to zero.
 */
void Image::clampNegatives()
{
    const TRaster::iterator last = raster_.end();
    for (TRaster::iterator i = raster_.begin(); i != last; ++i)
    {
        i->r = std::max(i->r, 0.f);
        i->g = std::max(i->g, 0.f);
        i->b = std::max(i->b, 0.f);
        i->a = std::max(i->a, 0.f);
    }
}



/** Apply a median filter on image.
 *  @param boxSize size of box filter, must be odd.
 *
 *  - Filters only pixels with alphachannel != 0.
 *  - We use the vector median filter for colour images, as described on page
 *    in GAUCH J. M. (1998). Noise Removal and contrast enhancement. In:
 *    Sangwine S. J. & Horne R. E. N. (Eds.) The Colour Image Processing
 *    Handbook. London, Chapman & Hall, 149-162.
 */
void Image::filterMedian(unsigned boxSize)
{
    if ((boxSize & 0x1) == 0)
    {
        LASS_THROW("boxSize '" << boxSize << "' isn't odd as requested.");
        return;
    }

    const unsigned boxArea = boxSize * boxSize;
    const int boxRadius = (boxSize - 1) / 2;

    TRaster box(boxArea);
    std::vector<float> distances(boxArea);

    for (unsigned y0 = 0; y0 < rows_; ++y0)
    {
        for (unsigned x0 = 0; x0 < cols_; ++x0)
        {
            TPixel& center = raster_[y0 * cols_ + x0];
            if (center.a == TNumTraits::zero)
            {
                continue; // no filtering on pixels with alphachannel == 0
            }

            // fill filterbox

            unsigned pixelsInBox = 0;
            int candidate = -1;
            for (int dy = -boxRadius; dy <= boxRadius; ++dy)
            {
                const int y = y0 + dy;
                const int offset = y * cols_;
                if (y >= 0 && y < signed(rows_))
                {
                    for (int dx = -boxRadius; dx <= boxRadius; ++dx)
                    {
                        const int x = x0 + dx;
                        if (x >= 0 && x < signed(cols_))
                        {
                            const TPixel& pixel = raster_[offset + x];
                            if (pixel.a != TNumTraits::zero)
                            {
                                box[pixelsInBox] = pixel;
                                if (dx == 0 && dy == 0)
                                {
                                    candidate = pixelsInBox;
                                }
                                ++pixelsInBox;
                            }
                        }
                    }
                }
            }

            // get median in filterbox
            //
            LASS_ASSERT(pixelsInBox > 0);
            LASS_ASSERT(candidate >= 0 && candidate < signed(pixelsInBox));
            unsigned i;
            for (i = 0; i < pixelsInBox; ++i)
            {
                distances[i] = 0.0;
                for (unsigned j = 0; j < pixelsInBox; ++j)
                {
                    distances[i] += prim::distance(box[i], box[j]);
                }
            }

            for (i = 0; i < pixelsInBox; ++i)
            {
                if (distances[i] < distances[candidate])
                {
                    candidate = i;
                }
            }

            LASS_ASSERT(candidate >= 0 && candidate < signed(pixelsInBox));
            center = box[candidate];
        }
    }
}



/** apply gamma correction to image
 */
void Image::filterGamma(TParam gammaExponent)
{
    const TRaster::size_type size = raster_.size();
    for (TRaster::size_type i = 0; i < size; ++i)
    {
        raster_[i] = raster_[i].gammaCorrected(gammaExponent);
    }
    colorSpace_.gamma *= gammaExponent;
}



/** apply exposure to image
 */
void Image::filterExposure(TParam exposureTime)
{
    const TRaster::size_type size = raster_.size();
    for (TRaster::size_type i = 0; i < size; ++i)
    {
        raster_[i] = raster_[i].exposed(exposureTime);
    }
}



/** apply exposure to image
 */
void Image::filterInverseExposure(TParam exposureTime)
{
    const TRaster::size_type size = raster_.size();
    for (TRaster::size_type i = 0; i < size; ++i)
    {
        raster_[i] = raster_[i].invExposed(exposureTime);
    }
}



// --- protected -----------------------------------------------------------------------------------




// --- private -------------------------------------------------------------------------------------

/** (re)allocate data chunck
 */
unsigned Image::resize(unsigned rows, unsigned cols)
{
    const unsigned size = rows * cols;
    raster_.resize(size);
    rows_ = rows;
    cols_ = cols;
    return size;
}



/** Open LASS Raw file.
 */
BinaryIStream& Image::openLass(BinaryIStream& stream)
{
    HeaderLass header;
    header.readFrom(stream);
    if (!stream || header.lass != magicLass_ || header.version > 3)
    {
        LASS_THROW_EX(BadFormat, "not a LASS RAW version 1 - 3 file.");
    }

    EndiannessSetter(stream, num::littleEndian);

    if (header.version >= 2)
    {
        for (size_t i = 0; i < numChromaticities; ++i)
        {
            num::Tfloat32 x, y;
            stream >> x >> y;
            colorSpace_[i] = TChromaticity(x, y);
        }
        colorSpace_.isFromFile = true;
    }
    else
    {
        colorSpace_ = defaultColorSpace();
    }

    if (header.version >= 3)
    {
        num::Tfloat32 g;
        stream >> g;
        colorSpace_.gamma = g;
    }

    resize(header.rows, header.cols);
    num::Tfloat32 r, g, b, a;
    for (TRaster::iterator i = raster_.begin(); i != raster_.end(); ++i)
    {
        stream >> r >> g >> b >> a;
        i->r = r;
        i->g = g;
        i->b = b;
        i->a = a;
    }

    return stream;
}



/** Open TARGA file.
 */
BinaryIStream& Image::openTarga(BinaryIStream& stream)
{
    HeaderTarga header;
    header.readFrom(stream);
    colorSpace_ = defaultColorSpace();
    colorSpace_.gamma = 2.2f;
    resize(header.imageHeight, header.imageWidth);

    switch (header.imageType)
    {
    case 2:
    case 10:
        openTargaTrueColor(stream, header);
        break;
    default:
        LASS_THROW_EX(BadFormat, "unsupported image type '" << static_cast<unsigned>(header.imageType) << "'");
        break;
    };

    return stream;
}



/** Open Type 2 and 11 TARGA file
 */
BinaryIStream& Image::openTargaTrueColor(BinaryIStream& stream, const HeaderTarga& iHeader)
{
    const TValue scale = num::inv(255.f);

    std::size_t numBytes = 0;
    switch (iHeader.imagePixelSize)
    {
    case 24: 
        numBytes = 3; 
        break;
    case 32:
        numBytes = 4;
        break;
    default:
        LASS_THROW_EX(BadFormat, "image pixel size '" << iHeader.imagePixelSize << "' not supported.");
    };

    LASS_ASSERT(cols_ == iHeader.imageWidth);
    const int xBegin = iHeader.flipHorizontalFlag() ? static_cast<int>(cols_) - 1 : 0;
    const int xEnd   = iHeader.flipHorizontalFlag() ? -1 : static_cast<int>(cols_);
    const int xDelta = iHeader.flipHorizontalFlag() ? -1 : 1;

    LASS_ASSERT(rows_ == iHeader.imageHeight);
    const int yBegin = iHeader.flipVerticalFlag() ? 0 : static_cast<int>(rows_) - 1;
    const int yEnd   = iHeader.flipVerticalFlag() ? static_cast<int>(rows_) : -1;
    const int yDelta = iHeader.flipVerticalFlag() ? 1 : -1;

    stream.seekg(iHeader.idLength + iHeader.colorMapLength * iHeader.colorMapEntrySize, 
        std::ios_base::cur);
    std::vector<impl::Bytes4> buffer(cols_);
    for (int y = yBegin; y != yEnd; y += yDelta)
    {   
        if (iHeader.imageType == 10)
        {
            // decode rle
            //
            unsigned x = 0;
            while (x < cols_)
            {
                num::Tuint8 code;
                stream >> code;
                const num::Tuint8 packetSize = (code & 0x7f) + 1;
                impl::Bytes4 bytes;
                if (code & 0x80)
                {
                    stream.read(bytes.get(), numBytes);
                    for (num::Tuint8 i = 0; i < packetSize; ++i)
                    {
                        LASS_ASSERT(x < cols_);
                        buffer[x++] = bytes;
                    }
                }
                else
                {
                    for (num::Tuint8 i = 0; i < packetSize; ++i)
                    {
                        stream.read(bytes.get(), numBytes);
                        LASS_ASSERT(x < cols_);
                        buffer[x++] = bytes;
                    }
                }
            }
        }
        else
        {
            LASS_ASSERT(iHeader.imageType == 2);
            for (unsigned x = 0; x < cols_; ++x)
            {
                stream.read(buffer[x].get(), numBytes);
            }
        }

        // decode scanline
        //
        TPixel* pixel = &raster_[y * cols_];
        for (int x = xBegin; x != xEnd; x += xDelta)
        {
            const impl::Bytes4& bytes = buffer[x];
            pixel->r = static_cast<TValue>(bytes[2]) * scale;
            pixel->g = static_cast<TValue>(bytes[1]) * scale;
            pixel->b = static_cast<TValue>(bytes[0]) * scale;
            pixel->a = numBytes == 3 ? TNumTraits::one : static_cast<TValue>(bytes[3]) * scale;
            ++pixel;
        }
    }

    return stream;
}



BinaryIStream& Image::openRadianceHdr(BinaryIStream& stream)
{
    HeaderRadianceHdr header;
    header.readFrom(stream);
    if (!stream)
    {
        LASS_THROW_EX(BadFormat, "syntax error in RADIANCE HDR header.");
    }

    if (header.isRgb)
    {
        for (size_t i = 0; i < numChromaticities; ++i)
        {
            colorSpace_[i] = TChromaticity(header.primaries[2 * i], header.primaries[2 * i + 1]);
        }
    }
    else
    {
        colorSpace_.red = TChromaticity(1, 0);
        colorSpace_.green = TChromaticity(0, 1);
        colorSpace_.blue = TChromaticity(0, 0);
        colorSpace_.white = TChromaticity(1.f / 3, 1.f / 3);
    }
    colorSpace_.gamma = 1;
    colorSpace_.isFromFile = true;

    float exponents[256];
    exponents[0] = 0.f;
    for (int i = 1; i < 256; ++i)
    {
        exponents[i] = ::ldexpf(1.f, i - 128 - 8);
    }
    float inverseCorrections[3];
    for (int i = 0; i < 3; ++i)
    {
        inverseCorrections[i] = num::inv(header.exposure * header.colorCorr[i]);
    }
    
    resize(header.height, header.width);

    const std::ptrdiff_t firstY = !header.yIncreasing ? 0 : (header.height - 1);    
    const std::ptrdiff_t lastY = !header.yIncreasing ? static_cast<std::ptrdiff_t>(header.height) : -1; 
    const std::ptrdiff_t deltaY = !header.yIncreasing ? 1 : -1;
    const std::ptrdiff_t firstX = header.xIncreasing ? 0 : (header.width - 1);
    const std::ptrdiff_t lastX = header.xIncreasing ? static_cast<std::ptrdiff_t>(header.width) : -1;
    const std::ptrdiff_t deltaX = header.xIncreasing ? 1 : -1;

    std::vector<impl::Bytes4> buffer(header.width);
    unsigned rleCount = 0;
    unsigned rleCountByte = 0;

    for (std::ptrdiff_t y = firstY; y != lastY; y += deltaY)
    {
        // unpack scanline to buffer
        //
        for (std::ptrdiff_t x = firstX; x != lastX; /* increment in loop */ )
        {
            impl::Bytes4 rgbe;
            stream.read(rgbe.get(), 4);
            if (rgbe[0] == 2 && rgbe[1] == 2 && (rgbe[2] & 0x80) == 0)
            {
                // new rle
                //
                const unsigned lineLength = rgbe[2] * 256 + rgbe[3];
                const ptrdiff_t lastX2 = x + lineLength * deltaX;
                for (unsigned k = 0; k < 4; ++k)
                {
                    ptrdiff_t x2 = x;
                    while (x2 != lastX2)
                    {
                        num::Tuint8 spanSize = 0, value = 0;
                        stream >> spanSize;
                        const bool isHomogenousSpan = spanSize > 128;
                        if (isHomogenousSpan) 
                        {
                            spanSize -= 128;
                            stream >> value;
                        }
                        for (num::Tuint8 i = spanSize; i > 0; --i)
                        {
                            if (!isHomogenousSpan)
                            {
                                stream >> value;
                            }
                            LASS_ASSERT(x2 != lastX2);
                            buffer[x2][k] = value;
                            x2 += deltaX;
                        }
                    }
                }
                x = lastX2;
            }
            else
            {
                // no rle or old rle
                //
                if (rgbe[0] == 1 && rgbe[1] == 1 && rgbe[2] == 1)
                {
                    rleCount |= rgbe[4] << rleCountByte;
                    ++rleCountByte;
                }
                else
                {
                    if (rleCount > 0)
                    {
                        for (unsigned k = rleCount - 1; k > 0; --k)
                        {
                            buffer[x] = rgbe;
                            x += deltaX;
                        }
                        rleCount = 0;
                        rleCountByte = 0;
                    }
                    buffer[x] = rgbe;
                    x += deltaX;
                }
            }
        }

        // decode rgbe information
        //
        TPixel* scanline = &raster_[y * header.width];  
        for (std::ptrdiff_t x = firstX; x != lastX; x += deltaX)
        {
            const impl::Bytes4 rgbe = buffer[x];
            TPixel& pixel = scanline[x];
            const float exponent = exponents[rgbe[3]];
            for (unsigned k = 0; k < 3; ++k)
            {
                pixel[k] = rgbe[k] * inverseCorrections[k] * exponent;
            }
        }
    }   
    return stream;
}



BinaryIStream& Image::openPfm(BinaryIStream& stream)
{
    HeaderPfm header;
    header.readFrom(stream);
    if (!stream)
    {
        LASS_THROW_EX(BadFormat, "not a PFM file.");
    }

    colorSpace_ = defaultColorSpace();
    colorSpace_.gamma = 1;

    resize(header.height, header.width);
    EndiannessSetter(stream, header.endianness);

    for (unsigned k = rows_; k > 0; --k)
    {
        const TRaster::iterator first = raster_.begin() + (k - 1) * cols_;
        const TRaster::iterator last = first + cols_;
        if (header.isGrey)
        {
            num::Tfloat32 y;
            for (TRaster::iterator i = first; i != last; ++i)
            {
                stream >> y;
                i->r = y;
                i->g = y;
                i->b = y;
                i->a = 1;
            }
        }
        else
        {
            num::Tfloat32 r, g, b;
            for (TRaster::iterator i = first; i != last; ++i)
            {
                stream >> r >> g >> b;
                i->r = r;
                i->g = g;
                i->b = b;
                i->a = 1;
            }
        }
    }

    return stream;
}



BinaryIStream& Image::openIgi(BinaryIStream& stream)
{
    HeaderIgi header;
    header.readFrom(stream);

    if (!stream || header.magic != magicIgi_ || header.version < 1 || header.version > 2)
    {
        LASS_THROW_EX(BadFormat, "not an IGI version <= 2 file.");
    }
    if (header.zipped)
    {
        LASS_THROW_EX(BadFormat, "cannot read zipped IGI files.");
    }
    if (header.dataSize < 0 || static_cast<num::Tuint32>(header.dataSize) != 12 * header.width * header.height)
    {
        LASS_THROW_EX(BadFormat, "error in dataSize field.");
    }

    // The current file format does not specify chromaticies, only distinguishes
    // between RGB and XYZ.  Use default RGB space in case of the former.
    colorSpace_ = header.rgb ? defaultColorSpace() : xyzColorSpace();
    colorSpace_.gamma = 1;
    colorSpace_.isFromFile = true;

    resize(header.height, header.width);
    num::Tfloat32 r, g, b;
    EndiannessSetter(stream, num::littleEndian);
    for (TRaster::iterator i = raster_.begin(); i != raster_.end(); ++i)
    {
        stream >> r >> g >> b;
        i->r = r;
        i->g = g;
        i->b = b;
        i->a = 1;
    }

    return stream;
}


BinaryOStream& Image::saveLass(BinaryOStream& stream) const
{
    HeaderLass header;
    header.lass = magicLass_;
    header.version = 2;
    header.rows = rows_;
    header.cols = cols_;
    header.writeTo(stream);

    EndiannessSetter(stream, num::littleEndian);
    
    for (size_t i = 0; i < numChromaticities; ++i)
    {
        const num::Tfloat32 x = colorSpace_[i].x;
        const num::Tfloat32 y = colorSpace_[i].y;
        stream << x << y;
    }

    const num::Tfloat32 c = colorSpace_.gamma;
    stream << c;

    num::Tfloat32 r, g, b, a;
    for (TRaster::const_iterator i = raster_.begin(); i != raster_.end(); ++i)
    {
        r = i->r;
        g = i->g;
        b = i->b;
        a = i->a;
        stream << r << g << b << a;
    }

    return stream;
}


/** Save TARGA file (type 2, 32 bit).
 */
BinaryOStream& Image::saveTarga(BinaryOStream& stream) const
{
    const TValue scale(255);
    const TValue zero(0);
    const TValue one(1);

    // STEP 1: Make a header of the right type
    HeaderTarga header;
    header.idLength = 0;
    header.colorMapType = 0;
    header.imageType = 10; // rle true color
    header.colorMapOrigin = 0;
    header.colorMapLength = 0;
    header.colorMapEntrySize = 0;
    header.imageXorigin = 0;
    header.imageYorigin = 0;
    header.imageWidth = cols_;
    header.imageHeight = rows_;
    header.imagePixelSize = 32;
    header.imageDescriptor = 0x08; // 8 attribute bits

    header.writeTo(stream);

    std::vector<impl::Bytes4> buffer(header.imageWidth);
    std::vector<impl::Bytes4> rleBuffer(128);
    for (unsigned y = rows_; y > 0; --y)
    {
        unsigned x;

        // encode in scanline buffer
        //
        const TPixel* scanline = &raster_[(y - 1) * cols_];
        for (x = 0; x < cols_; ++x)
        {
            const TPixel& pixel = scanline[x];
            impl::Bytes4& bytes = buffer[x];
            bytes[0] = static_cast<num::Tuint8>(num::clamp(pixel.b, zero, one) * scale);
            bytes[1] = static_cast<num::Tuint8>(num::clamp(pixel.g, zero, one) * scale);
            bytes[2] = static_cast<num::Tuint8>(num::clamp(pixel.r, zero, one) * scale);
            bytes[3] = static_cast<num::Tuint8>(num::clamp(pixel.a, zero, one) * scale);
        }

        // run-length encode buffer
        //
        unsigned totalLength = 0;
        num::Tuint8 numDiff = 0;
        x = 0;
        while (x < cols_)
        {
            const impl::Bytes4& bytes = buffer[x];
            unsigned x2 = x;
            num::Tuint8 numSame = 0;
            while (x2 < cols_ && numSame < 128 && buffer[x2] == bytes)
            {
                ++x2;
                ++numSame;
            }
            if (numSame == 1)
            {
                rleBuffer[numDiff] = bytes;
                ++numDiff;
                ++x;
            }
            if (numDiff == 128 || ((numSame > 1 || x == cols_) && numDiff > 0))
            {
                stream << static_cast<num::Tuint8>(numDiff - 1);
                for (num::Tuint8 i = 0; i < numDiff; ++i)
                {
                    stream.write(&rleBuffer[i], 4);
                }
                totalLength += numDiff;
                LASS_ASSERT(totalLength == x);
                numDiff = 0;
            }
            if (numSame > 1)
            {
                stream << static_cast<num::Tuint8>((numSame - 1) | 0x80);
                stream.write(bytes.get(), 4);
                x = x2;
                totalLength += numSame;
                LASS_ASSERT(totalLength == x);
                numSame = 0;
            }
        }
        LASS_ASSERT(totalLength == cols_);
    }

    return stream;
}


/** Save RADIANCE HDR
 */
BinaryOStream& Image::saveRadianceHdr(BinaryOStream& stream) const
{
    if (cols_ > 0x7fff)
    {
        LASS_THROW_EX(BadFormat, "cannot save this as RADIANCE HDR, because image is too wide");
    }
    HeaderRadianceHdr header;
    header.height = rows_;
    header.width = cols_;
    header.yIncreasing = false;
    header.xIncreasing = true;
    header.isRgb = colorSpace_ != xyzColorSpace();
    for (size_t i = 0; i < numChromaticities; ++i)
    {
        header.primaries[2 * i] = colorSpace_[i].x;
        header.primaries[2 * i + 1] = colorSpace_[i].y;
    }
    header.writeTo(stream);

    std::vector<impl::Bytes4> buffer(cols_);
    std::vector<num::Tuint8> rleBuffer(128);

    for (unsigned y = 0; y < rows_; ++y)
    {
        // first, transform a line of rgb pixels to rgbe reprentation
        //
        const TPixel* line = &raster_[y * cols_];
        for (unsigned x = 0; x < cols_; ++x)
        {
            const TPixel& pixel = line[x];
            impl::Bytes4& rgbe = buffer[x];
            const float maximum = std::max(std::max(pixel.r, pixel.g), pixel.b);
            if (maximum < 1e-32)
            {
                rgbe[0] = rgbe[1] = rgbe[2] = rgbe[3] = 0;
            }
            else
            {
                int exponent;
                const float mantissa = ::frexpf(maximum, &exponent);
                for (unsigned k = 0; k < 3; ++k)
                {
                    const float normalized = pixel[k] * (256.f * mantissa / maximum);
                    rgbe[k] = static_cast<num::Tuint8>(num::clamp(normalized, 0.f, 255.f));
                }
                rgbe[3] = static_cast<num::Tuint8>(num::clamp(exponent + 128, 0, 255));
            }
        }

        // rle encode each channel
        //
        num::Tuint8 bytes[4];
        bytes[0] = 2;
        bytes[1] = 2;
        bytes[2] = (cols_ & 0x7f00) >> 8;
        bytes[3] = cols_ & 0xff;
        stream.write(bytes, 4);

        for (unsigned k = 0; k < 4; ++k)
        {
            num::Tuint8 numDiff = 0;
            unsigned x = 0;
            while (x < cols_)
            {
                num::Tuint8 value = buffer[x][k];
                unsigned x2 = x;
                num::Tuint8 numSame = 0;
                while (x2 < cols_ && numSame < 127 && buffer[x2][k] == value)
                {
                    ++x2;
                    ++numSame;
                }
                if (numSame > 2)
                {
                    if (numDiff > 0)
                    {
                        stream << numDiff;
                        stream.write(&rleBuffer[0], numDiff);
                        numDiff = 0;
                    }
                    numSame += 128;
                    stream << numSame << value;
                    x = x2;
                }
                else
                {
                    if (numDiff == 128)
                    {
                        stream << numDiff;
                        stream.write(&rleBuffer[0], numDiff);
                        numDiff = 0;
                    }
                    rleBuffer[numDiff] = value;
                    ++numDiff;
                    ++x;
                }
            }
            if (numDiff > 0)
            {
                stream << numDiff;
                stream.write(&rleBuffer[0], numDiff);
            }
        }
    }
    return stream;
}



BinaryOStream& Image::savePfm(BinaryOStream& stream) const
{
    HeaderPfm header;
    header.height = rows_;
    header.width = cols_;
    header.writeTo(stream);

    EndiannessSetter(stream, header.endianness);

    for (unsigned k = rows_; k > 0; --k)
    {
        const TRaster::const_iterator first = raster_.begin() + (k - 1) * cols_;
        const TRaster::const_iterator last = first + cols_;
        for (TRaster::const_iterator i = first; i != last; ++i)
        {
            const num::Tfloat32 r = i->r;
            const num::Tfloat32 g = i->g;
            const num::Tfloat32 b = i->b;
            stream << r << g << b;
        }
    }

    return stream;
}



BinaryOStream& Image::saveIgi(BinaryOStream& stream) const
{
    HeaderIgi header;
    header.magic = magicIgi_;
    header.version = 1;
    header.numSamples = rows_ * cols_;
    header.width = cols_;
    header.height = rows_;
    header.superSampling = 1;
    header.zipped = 0;
    header.dataSize = 12 * rows_ * cols_;
    header.rgb = colorSpace_ == xyzColorSpace() ? 0 : 1;
    header.writeTo(stream);

    EndiannessSetter(stream, num::littleEndian);

    for (TRaster::const_iterator i = raster_.begin(); i != raster_.end(); ++i)
    {
        const num::Tfloat32 r = i->r;
        const num::Tfloat32 g = i->g;
        const num::Tfloat32 b = i->b;
        stream << r << g << b;
    }

    return stream;
}



Image::FileFormat Image::findFormat(const std::string& formatTag)
{
    const std::string key = stde::tolower(formatTag);
    TFileFormats::const_iterator i = fileFormats_.find(key);
    if (i == fileFormats_.end())
    {
        LASS_THROW_EX(BadFormat, "unknown fileformat '" << key << "'.");
    }
    return i->second;
}



BinaryIStream& Image::readLine(BinaryIStream& stream, std::string& line)
{
    std::string result;
    while (stream.good())
    {
        char character;
        stream >> character;
        if (stream.good())
        {
            if (character == '\n')
            {
                line.swap(result);
            }
            else
            {
                result += character;
            }
        }
    }
    return stream;
}



BinaryOStream& Image::writeLine(BinaryOStream& stream, const std::string& iString)
{
    stream.write(iString.data(), iString.size());
    stream << '\n';
    return stream;
}



Image::TFileFormats Image::fillFileFormats()
{
    TFileFormats formats;
    formats["lass"] = FileFormat(&Image::openLass, &Image::saveLass);
    formats["targa"] = FileFormat(&Image::openTarga, &Image::saveTarga);
    formats["tga"] = formats["targa"];
    formats["hdr"] = FileFormat(&Image::openRadianceHdr, &Image::saveRadianceHdr);
    formats["pic"] = formats["hdr"];
    formats["rgbe"] = formats["hdr"];
    formats["pfm"] = FileFormat(&Image::openPfm, &Image::savePfm);
    formats["igi"] = FileFormat(&Image::openIgi, &Image::saveIgi);
    return formats;
}



/** return sRGB as colorSpace
 */
const Image::ColorSpace Image::defaultColorSpace()
{
    ColorSpace result;
    result.red = TChromaticity(0.6400f, 0.3300f);
    result.green = TChromaticity(0.3000f, 0.6000f);
    result.blue = TChromaticity(0.1500f, 0.0600f);
    result.white = TChromaticity(0.3127f, 0.3290f);
    result.gamma = 1;
    result.isFromFile = false;
    return result;
}



const Image::ColorSpace Image::xyzColorSpace()
{
    ColorSpace result;
    result.red = TChromaticity(1.f, 0.f);
    result.green = TChromaticity(0.f, 1.f);
    result.blue = TChromaticity(0.f, 0.f);
    result.white = TChromaticity(1.f / 3, 1.f / 3);
    result.gamma = 1;
    result.isFromFile = false;
    return result;
}



// --- HeaderLass -----------------------------------------------------------------------------------

void Image::HeaderLass::readFrom(BinaryIStream& stream)
{
    EndiannessSetter(stream, num::littleEndian);
    stream >> lass >> version >> rows >> cols;
}



void Image::HeaderLass::writeTo(BinaryOStream& stream)
{
    EndiannessSetter(stream, num::littleEndian);
    stream << lass << version << rows << cols;
}



// --- HeaderTarga ---------------------------------------------------------------------------------

void Image::HeaderTarga::readFrom(BinaryIStream& stream)
{
    EndiannessSetter(stream, num::littleEndian);
    stream >> idLength >> colorMapType >> imageType >> colorMapOrigin >> colorMapLength >>
        colorMapEntrySize >> imageXorigin >> imageYorigin >> imageWidth >> imageHeight >>
        imagePixelSize >> imageDescriptor;
}



void Image::HeaderTarga::writeTo(BinaryOStream& stream)
{
    EndiannessSetter(stream, num::littleEndian);
    stream << idLength << colorMapType << imageType << colorMapOrigin << colorMapLength <<
        colorMapEntrySize << imageXorigin << imageYorigin << imageWidth << imageHeight <<
        imagePixelSize << imageDescriptor;
}



// --- HeaderRadianceHdr ---------------------------------------------------------------------------

Image::HeaderRadianceHdr::HeaderRadianceHdr():
    exposure(1.f),
    height(0),
    width(0),
    yIncreasing(false),
    xIncreasing(true),
    isRgb(true),
    isDefaultPrimaries(true)
{
    std::fill_n(colorCorr, static_cast<int>(sizeColorCorr), 1.f);
    const float defaultPrimaries[sizePrimaries] = 
        { 0.640f, 0.330f, 0.290f, 0.600f, 0.150f, 0.060f, 0.333f, 0.333f };
    stde::copy_n(defaultPrimaries, static_cast<int>(sizePrimaries), primaries);
}

void Image::HeaderRadianceHdr::readFrom(BinaryIStream& stream)
{
    std::size_t magicSize = magicRadiance_.size();
    std::vector<char> magic(magicSize);
    stream.read(&magic[0], magicSize);
    if (!stream.good() || !stde::equal_r(magicRadiance_, magic))
    {
        LASS_THROW_EX(BadFormat, "file is not of RADIANCE file format");
    }

    // first, read the real header
    //
    while (true)
    {
        std::string line;
        readLine(stream, line);
        if (!stream.good())
        {
            LASS_THROW_EX(BadFormat, "syntax error in header of RADIANCE HDR file");
        }
        if (line.empty())
        {
            break;
        }
        if (stde::begins_with(line, std::string("#")))
        {
            continue;
        }
        std::vector<std::string> splitted = stde::split(line, std::string("="), 1);
        if (splitted.size() != 2)
        {
            LASS_THROW_EX(BadFormat, "syntax error in header of RADIANCE HDR file");
        }
        std::string command = stde::toupper(splitted[0]);
        std::string value = stde::strip(splitted[1]);
        if (command == "FORMAT")
        {
            if (value == "32-bit_rle_rgbe")
            {
                isRgb = true;
            }
            else if (value == "32-bit_rle_xyze")
            {
                isRgb = false;
            }
            else
            {
                LASS_THROW_EX(BadFormat, "unknown value for FORMAT field of header of RADIANCE HDR file");
            }
        }
        else if (command == "EXPOSURE")
        {
            exposure *= util::stringCast<float>(value);
        }
        else if (command == "COLORCORR")
        {
            std::vector<std::string> values = stde::split(value);
            if (values.size() != sizeColorCorr)
            {
                LASS_THROW_EX(BadFormat, "syntax error in COLORCORR field of header of RADIANCE HDR file");
            }
            stde::transform_r(values, colorCorr, util::stringCast<float, std::string>);
        }
        else if (command == "PRIMARIES")
        {
            std::vector<std::string> values = stde::split(value);
            if (values.size() != sizePrimaries)
            {
                LASS_THROW_EX(BadFormat, "syntax error in PRIMARIES field of header of RADIANCE HDR file");
            }
            stde::transform_r(values, primaries, util::stringCast<float, std::string>);
            isDefaultPrimaries = false;
        }
    }

    // second, interpret the resolution line
    std::string line;
    readLine(stream, line);
    if (!stream.good())
    {
        LASS_THROW_EX(BadFormat, "syntax error in resolution line of RADIANCE HDR file");
    }
    std::vector<std::string> splitted = stde::split(line);
    if (splitted.size() != 4)
    {
        LASS_THROW_EX(BadFormat, "resolution line of RADIANCE HDR file not of 4 elements");
    }
    std::string y = stde::toupper(splitted[0]);
    std::string x = stde::toupper(splitted[2]);
    if (!(y == "+Y" || y == "-Y") || !(x == "+X" || x == "-X"))
    {
        LASS_THROW_EX(BadFormat, "syntax error in resolution line of RADIANCE HDR file");
    }
    yIncreasing = y == "+Y";
    xIncreasing = x == "+X";
    height = util::stringCast<unsigned>(splitted[1]);
    width = util::stringCast<unsigned>(splitted[3]);
}



void Image::HeaderRadianceHdr::writeTo(BinaryOStream& stream)
{
    stream.write(magicRadiance_.data(), magicRadiance_.length());
    writeLine(stream, "SOFTWARE=LASS, http://lass.sourceforge.net");
    writeLine(stream, std::string("FORMAT=32-bit_rle_") + (isRgb ? "rgbe" : "xyze"));
    writeLine(stream, "EXPOSURE=" + util::stringCast<std::string>(exposure));
    writeLine(stream, std::string("COLORCORR=") + 
        stde::join(std::string(" "), colorCorr, colorCorr + sizeColorCorr));
    writeLine(stream, std::string("PRIMARIES=") + 
        stde::join(std::string(" "), primaries, primaries + sizePrimaries));
    writeLine(stream, "");
    std::ostringstream resolution;
    resolution << (yIncreasing ? "+Y" : "-Y") << " " << height;
    resolution << " " << (xIncreasing ? "+X" : "-X") << " " << width;
    writeLine(stream, resolution.str());
}



// --- HeaderPfm -----------------------------------------------------------------------------------

Image::HeaderPfm::HeaderPfm():
    width(0),
    height(0),
    aspect(1),
    endianness(num::littleEndian),
    isGrey(false)   
{
}



void Image::HeaderPfm::readFrom(BinaryIStream& stream)
{
    const std::string magicPF = "PF";
    const std::string magicPf = "Pf";
    LASS_ASSERT(magicPF.length() == magicPf.length());
    const size_t magicSize = magicPF.length();
    std::vector<char> magic(magicSize);
    stream.read(&magic[0], magicSize);
    if (!stream.good() || !(stde::equal_r(magicPF, magic) || stde::equal_r(magicPf, magic)))
    {
        LASS_THROW_EX(BadFormat, "file is not a PFM file");
    }

    isGrey = stde::equal_r(magicPf, magic);

    // we need to read a number of attributes that may be spread across one or more lines
    //
    const size_t numAttributes = 3;
    std::string attributes[numAttributes];
    size_t k = 0;
    std::string line;
    std::string attr;
    while (k < numAttributes)
    {
        Image::readLine(stream, line);
        if (!stream.good())
        {
            LASS_THROW_EX(BadFormat, "syntax error in header of PFM file");
        }
        const size_t startComments = line.find("#");
        std::istringstream buffer(line.substr(0, startComments));
        while (k < numAttributes && buffer.good())
        {
            buffer >> attr;
            if (buffer.good())
            {
                attributes[k++] = attr;
            }
        }
    }

    try
    {
        width = util::stringCast<unsigned>(attributes[0]);
        height = util::stringCast<unsigned>(attributes[1]);
        aspect = util::stringCast<float>(attributes[2]);
    }
    catch (const util::BadStringCast&)
    {
        LASS_THROW_EX(BadFormat, "syntax error in header of PFM file");
    }

    endianness = aspect < 0 ? num::littleEndian : num::bigEndian;
    aspect = num::abs(aspect);
}



void Image::HeaderPfm::writeTo(BinaryOStream& stream)
{
    std::ostringstream buffer;
    buffer << "PF\n" << width << " " << height << "\n" << (endianness == num::littleEndian ? -aspect : aspect);
    writeLine(stream, buffer.str());
}



// --- HeaderIgi -----------------------------------------------------------------------------------

void Image::HeaderIgi::readFrom(BinaryIStream& stream)
{
    EndiannessSetter(stream, num::littleEndian);
    stream >> magic >> version >> numSamples >> width >> height >> superSampling >> zipped
        >> dataSize >> rgb;
    stream.seekg(padding, std::ios_base::cur);
}



void Image::HeaderIgi::writeTo(BinaryOStream& stream)
{
    EndiannessSetter(stream, num::littleEndian);
    stream << magic << version << numSamples << width << height << superSampling << zipped
        << dataSize << rgb;
    stream.seekp(padding, std::ios_base::cur);
}

// --- free ----------------------------------------------------------------------------------------



}

}

// EOF