如何检测扫描文档的方向？
我会检测并在必要时纠正扫描文档图像的方向。我已经能够对文档进行歪斜校正，但仍然可能会发生文档颠倒的情况，需要将其旋转 180°。
使用 tesseract 的布局分析功能，应该可以确定文档的方向代码：
tesseract::TessBaseAPI api;
api.Init(argv[0], "eng");
api.SetImage(img);
api.SetPageSegMode(tesseract::PSM_AUTO_OSD);
tesseract::PageIterator* it = api.AnalyseLayout();
tesseract::Orientation orient;
tesseract::WritingDirection dir;
tesseract::TextlineOrder order;
float f;
it->Orientation(&orient, &dir, &order, &f);
if(orient == tesseract::Orientation::ORIENTATION_PAGE_UP)
std::cout << "Page Up\t";
else if(orient == tesseract::Orientation::ORIENTATION_PAGE_LEFT)
std::cout << "Page Left\t";
else if(orient == tesseract::Orientation::ORIENTATION_PAGE_DOWN)
std::cout << "Page Down\t";
else if(orient == tesseract::Orientation::ORIENTATION_PAGE_RIGHT)
std::cout << "Page Right\t";
但是，该代码似乎无法正常工作，因为当文档采用纵向格式时，它总是返回 ORIENTATION_PAGE_UP ，而当文档采用横向格式时，它总是返回 ORIENTATION_PAGE_LEFT 。 （可以使用ORIENTATION_PAGE_DOWN和ORIENTATION_PAGE_RIGHT，但永远不会返回）。
A.) 上面的代码有什么问题吗？
B.) 我还能如何确定文档方向？
I'd to detect and, if necessary, correct the orientation of a scanned document image. I am already able to deskew documents, however it still might occur, that a document is upside down and it needs to be rotated by 180°.
Using tesseract's layout analysis feature it should be possible to determine a document's orientation using this code:
tesseract::TessBaseAPI api;
api.Init(argv[0], "eng");
api.SetImage(img);
api.SetPageSegMode(tesseract::PSM_AUTO_OSD);
tesseract::PageIterator* it = api.AnalyseLayout();
tesseract::Orientation orient;
tesseract::WritingDirection dir;
tesseract::TextlineOrder order;
float f;
it->Orientation(&orient, &dir, &order, &f);
if(orient == tesseract::Orientation::ORIENTATION_PAGE_UP)
std::cout << "Page Up\t";
else if(orient == tesseract::Orientation::ORIENTATION_PAGE_LEFT)
std::cout << "Page Left\t";
else if(orient == tesseract::Orientation::ORIENTATION_PAGE_DOWN)
std::cout << "Page Down\t";
else if(orient == tesseract::Orientation::ORIENTATION_PAGE_RIGHT)
std::cout << "Page Right\t";
However the code doesn't seems to work correctly as it always returns ORIENTATION_PAGE_UP when a document is in portrait format and ORIENTATION_PAGE_LEFT when it is in landscape format. (ORIENTATION_PAGE_DOWN and ORIENTATION_PAGE_RIGHT can be used, but are never returned).
A.) Is there anything wrong with the code above?
B.) How else can I determine a documents orientation?
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评论（1）
只运行检测来评估检测率，然后翻转做同样的事情怎么样？更好的速率给出了正确的方向。
What about just running your detection evaluate the detection rate and then doing the same thing flipped ? The better rate gives the right direction.