exiv2/src/bmpimage.cpp

// ***************************************************************** -*- C++ -*-
/*
 * Copyright (C) 2004-2021 Exiv2 authors
 * This program is part of the Exiv2 distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, 5th Floor, Boston, MA 02110-1301 USA.
 */
/*
  File:      bmpimage.cpp
  Author(s): Marco Piovanelli, Ovolab (marco)
  History:   05-Mar-2007, marco: created
 */
// *****************************************************************************
// included header files
#include "config.h"

#include "basicio.hpp"
#include "bmpimage.hpp"
#include "error.hpp"
#include "futils.hpp"
#include "image.hpp"

// + standard includes
#include <cstring>
#include <iostream>
#include <string>

// *****************************************************************************
// class member definitions
namespace Exiv2
{
    BmpImage::BmpImage(BasicIo::UniquePtr io) : Image(ImageType::bmp, mdNone, std::move(io))
    {
    }

    std::string BmpImage::mimeType() const
    {
        // "image/bmp" is a Generic Bitmap
        return "image/x-ms-bmp"; // Microsoft Bitmap
    }

    void BmpImage::setExifData(const ExifData& /*exifData*/)
    {
        throw(Error(kerInvalidSettingForImage, "Exif metadata", "BMP"));
    }

    void BmpImage::setIptcData(const IptcData& /*iptcData*/)
    {
        throw(Error(kerInvalidSettingForImage, "IPTC metadata", "BMP"));
    }

    void BmpImage::setComment(std::string_view /*comment*/)
    {
        throw(Error(kerInvalidSettingForImage, "Image comment", "BMP"));
    }

    void BmpImage::readMetadata()
    {
#ifdef EXIV2_DEBUG_MESSAGES
        std::cerr << "Exiv2::BmpImage::readMetadata: Reading Windows bitmap file " << io_->path() << "\n";
#endif
        if (io_->open() != 0) {
            throw Error(kerDataSourceOpenFailed, io_->path(), strError());
        }
        IoCloser closer(*io_);

        // Ensure that this is the correct image type
        if (!isBmpType(*io_, false)) {
            if (io_->error() || io_->eof())
                throw Error(kerFailedToReadImageData);
            throw Error(kerNotAnImage, "BMP");
        }
        clearMetadata();

        /*
          The Windows bitmap header goes as follows -- all numbers are in little-endian byte order:

          offset  length   name                   description
          ======  =======  =====================  =======
           0      2 bytes  signature              always 'BM'
           2      4 bytes  bitmap size
           6      4 bytes  reserved
          10      4 bytes  bitmap offset
          14      4 bytes  header size
          18      4 bytes  bitmap width
          22      4 bytes  bitmap height
          26      2 bytes  plane count
          28      2 bytes  depth
          30      4 bytes  compression            0 = none; 1 = RLE, 8 bits/pixel; 2 = RLE, 4 bits/pixel; 3 = bitfield; 4 = JPEG; 5 = PNG
          34      4 bytes  image size             size of the raw bitmap data, in bytes
          38      4 bytes  horizontal resolution  (in pixels per meter)
          42      4 bytes  vertical resolution    (in pixels per meter)
          46      4 bytes  color count
          50      4 bytes  important colors       number of "important" colors
        */
        byte buf[26];
        if (io_->read(buf, sizeof(buf)) == sizeof(buf)) {
            pixelWidth_ = getLong(buf + 18, littleEndian);
            pixelHeight_ = getLong(buf + 22, littleEndian);
        }
    }

    void BmpImage::writeMetadata()
    {
        /// \todo implement me!
        throw(Error(kerWritingImageFormatUnsupported, "BMP"));
    }

    // *************************************************************************
    // free functions
    Image::UniquePtr newBmpInstance(BasicIo::UniquePtr io, bool /*create*/)
    {
        auto image = std::make_unique<BmpImage>(std::move(io));
        if (!image->good()) {
            image.reset();
        }
        return image;
    }

    bool isBmpType(BasicIo& iIo, bool advance)
    {
        const int32_t len = 2;
        const unsigned char BmpImageId[2] = {'B', 'M'};
        byte buf[len];
        iIo.read(buf, len);
        if (iIo.error() || iIo.eof()) {
            return false;
        }
        bool matched = (memcmp(buf, BmpImageId, len) == 0);
        if (!advance || !matched) {
            iIo.seek(-len, BasicIo::cur);
        }
        return matched;
    }
}  // namespace Exiv2