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C-API for OSResults (orientation and script results) is not a stable ABI #424

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jbarlow83 opened this issue Sep 8, 2016 · 7 comments
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C-API for OSResults (orientation and script results) is not a stable ABI #424

jbarlow83 opened this issue Sep 8, 2016 · 7 comments
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OSD Orientation and Script Detection

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@jbarlow83
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The existing C API for TessBaseAPIDetectOS requires a C caller to successfully allocate struct OSResults which is actually a C++ class. If the C++ compiler decides to append anything to the structure, this will fail. The definition of this struct also depends on kMaxNumberOfScripts so is subject to change if (when) Tesseract adds more scripts.

The struct members that a caller is most likely to want are actually in OSBestResult whose position may shift.

I suggest deprecating this API and providing one that returns the member elements of OSBestResult instead. I think it would be useful to have a C API call to obtain this information rather than parsing the executable's output in -psm 0. Here's one possible API.

BOOL TessBaseAPIDetectOS2(
 TessBaseAPI* handle, 
 int* best_script_id, 
 int* best_orientation_id, 
 float* script_confidence, 
 float* orientation_confidence);

Returning OSBestResults is also an option, but sometimes it's nice to avoid structs entirely.

I can contribute changes if there's agreement on them.
@zdenop
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zdenop commented Sep 9, 2016

Thank you for you investigation.
Can you please post it to tesseract-dev forum for discussion, so developers of tesseract wrappers can be aware of change?

@jbarlow83
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@amitdo
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amitdo commented Dec 5, 2016 •
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The suggestion looks good to me.

@zdenop, I suggest to give @jbarlow83 a green light for sending a PR.

@stweil
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stweil commented Dec 5, 2016

I must admit that I had to look into the code what "OS" means in the context of OCR. Maybe it is possible to find a better name with "Orientation and Script" ("OaS"?).

PS. I just noted that the title of this issue also had the information which I was looking for.

@zdenop
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zdenop commented Dec 7, 2016

@jbarlow83 will you create PR?

@jbarlow83
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Yes, working on it.

jbarlow83 pushed a commit to jbarlow83/tesseract that referenced this issue Dec 7, 2016
Implement a new orientation and script detection API for C and C++
bc95798 
See issue tesseract-ocr#424.

The existing C API for TessBaseAPIDetectOS requires a C caller to successfully allocate struct OSResults which is actually a C++ class.  Generally it won't
be possible for a regular C compiler to do this properly.

It's also assumed that most API level users of Tesseract are only interested in Tesseract's best guess as to script and orientation, not the individual values for all possible scripts.

This introduces a new API with a better name that is more closely aligned with the output of 'tesseract -psm 0'.  Both tesseract -psm 0 and this API now share the same code in baseapi.cpp.
@zdenop
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zdenop commented Dec 9, 2016

fixed with 3a47adc

@zdenop zdenop closed this as completed Dec 9, 2016
zdenop pushed a commit that referenced this issue Dec 11, 2016
@zdenop
Implement a new orientation and script detection API for C and C++
bdb690b 
See issue #424.

The existing C API for TessBaseAPIDetectOS requires a C caller to successfully allocate struct OSResults which is actually a C++ class.  Generally it won't
be possible for a regular C compiler to do this properly.

It's also assumed that most API level users of Tesseract are only interested in Tesseract's best guess as to script and orientation, not the individual values for all possible scripts.

This introduces a new API with a better name that is more closely aligned with the output of 'tesseract -psm 0'.  Both tesseract -psm 0 and this API now share the same code in baseapi.cpp.
@jflesch jflesch mentioned this issue Feb 28, 2017
Closed
@amitdo amitdo added the OSD Orientation and Script Detection label May 14, 2020
zvezdochiot pushed a commit to ImageProcessing-ElectronicPublications/tesseract that referenced this issue Mar 28, 2021
@zdenop
Implement a new orientation and script detection API for C and C++
81bc5b5 
See issue tesseract-ocr#424.

The existing C API for TessBaseAPIDetectOS requires a C caller to successfully allocate struct OSResults which is actually a C++ class.  Generally it won't
be possible for a regular C compiler to do this properly.

It's also assumed that most API level users of Tesseract are only interested in Tesseract's best guess as to script and orientation, not the individual values for all possible scripts.

This introduces a new API with a better name that is more closely aligned with the output of 'tesseract -psm 0'.  Both tesseract -psm 0 and this API now share the same code in baseapi.cpp.
zvezdochiot pushed a commit to ImageProcessing-ElectronicPublications/tesseract that referenced this issue Mar 28, 2021
@zdenop
Implement a new orientation and script detection API for C and C++
968e18f 
See issue tesseract-ocr#424.

The existing C API for TessBaseAPIDetectOS requires a C caller to successfully allocate struct OSResults which is actually a C++ class.  Generally it won't
be possible for a regular C compiler to do this properly.

It's also assumed that most API level users of Tesseract are only interested in Tesseract's best guess as to script and orientation, not the individual values for all possible scripts.

This introduces a new API with a better name that is more closely aligned with the output of 'tesseract -psm 0'.  Both tesseract -psm 0 and this API now share the same code in baseapi.cpp.
zvezdochiot pushed a commit to ImageProcessing-ElectronicPublications/tesseract that referenced this issue Mar 28, 2021
@zdenop
Implement a new orientation and script detection API for C and C++
c27c3ca 
See issue tesseract-ocr#424.

The existing C API for TessBaseAPIDetectOS requires a C caller to successfully allocate struct OSResults which is actually a C++ class.  Generally it won't
be possible for a regular C compiler to do this properly.

It's also assumed that most API level users of Tesseract are only interested in Tesseract's best guess as to script and orientation, not the individual values for all possible scripts.

This introduces a new API with a better name that is more closely aligned with the output of 'tesseract -psm 0'.  Both tesseract -psm 0 and this API now share the same code in baseapi.cpp.
zvezdochiot pushed a commit to ImageProcessing-ElectronicPublications/tesseract that referenced this issue Mar 28, 2021
@zdenop
Implement a new orientation and script detection API for C and C++
017ef47 
See issue tesseract-ocr#424.

The existing C API for TessBaseAPIDetectOS requires a C caller to successfully allocate struct OSResults which is actually a C++ class.  Generally it won't
be possible for a regular C compiler to do this properly.

It's also assumed that most API level users of Tesseract are only interested in Tesseract's best guess as to script and orientation, not the individual values for all possible scripts.

This introduces a new API with a better name that is more closely aligned with the output of 'tesseract -psm 0'.  Both tesseract -psm 0 and this API now share the same code in baseapi.cpp.
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@zdenop @jbarlow83 @stweil @amitdo