Method readMetadata

src/psdimage.cpp:115–211

}

void PsdImage::readMetadata() {
#ifdef EXIV2_DEBUG_MESSAGES
  std::cerr << "Exiv2::PsdImage::readMetadata: Reading Photoshop file " << io_->path() << "\n";
#endif
  if (io_->open() != 0) {
    throw Error(ErrorCode::kerDataSourceOpenFailed, io_->path(), strError());
  }
  IoCloser closer(*io_);
  // Ensure that this is the correct image type
  if (!isPsdType(*io_, false)) {
    if (io_->error() || io_->eof())
      throw Error(ErrorCode::kerFailedToReadImageData);
    throw Error(ErrorCode::kerNotAnImage, "Photoshop");
  }
  clearMetadata();

  /*
    The Photoshop header goes as follows -- all numbers are in big-endian byte order:

    offset  length   name       description
    ======  =======  =========  =========
     0      4 bytes  signature  always '8BPS'
     4      2 bytes  version    always equal to 1
     6      6 bytes  reserved   must be zero
    12      2 bytes  channels   number of channels in the image, including alpha channels (1 to 24)
    14      4 bytes  rows       the height of the image in pixels
    18      4 bytes  columns    the width of the image in pixels
    22      2 bytes  depth      the number of bits per channel
    24      2 bytes  mode       the color mode of the file; Supported values are: Bitmap=0; Grayscale=1;
    Indexed=2; RGB=3; CMYK=4; Multichannel=7; Duotone=8; Lab=9
  */
  byte buf[26];
  if (io_->read(buf, 26) != 26) {
    throw Error(ErrorCode::kerNotAnImage, "Photoshop");
  }
  pixelWidth_ = getLong(buf + 18, bigEndian);
  pixelHeight_ = getLong(buf + 14, bigEndian);

  // immediately following the image header is the color mode data section,
  // the first four bytes of which specify the byte size of the whole section
  if (io_->read(buf, 4) != 4) {
    throw Error(ErrorCode::kerNotAnImage, "Photoshop");
  }

  // skip it
  if (io_->seek(getULong(buf, bigEndian), BasicIo::cur)) {
    throw Error(ErrorCode::kerNotAnImage, "Photoshop");
  }

  // after the color data section, comes a list of resource blocks, preceded by the total byte size
  if (io_->read(buf, 4) != 4) {
    throw Error(ErrorCode::kerNotAnImage, "Photoshop");
  }
  uint32_t resourcesLength = getULong(buf, bigEndian);
  Internal::enforce(resourcesLength < io_->size(), Exiv2::ErrorCode::kerCorruptedMetadata);

  while (resourcesLength > 0) {
    Internal::enforce(resourcesLength >= 8, Exiv2::ErrorCode::kerCorruptedMetadata);