in src/tiffDirectory.cpp [244:251]
bool TiffDirectory::isExtractablePyramidImage() const {
return ((isJpegCompressed() || isJpeg2kCompressed()) && isPyramidImage() &&
(isPhotoMetricYCBCR() || isPhotoMetricRGB()) &&
(tileCount() > 0) && (tileWidth() > 0) && (tileHeight() > 0) &&
(imageWidth() > 0) && (imageHeight() > 0) &&
((imageDepth() == 1) ||
(tilesPerRow() * tilesPerColumn() == tileCount())));
}