I am trying to call this cpp function from python:
TESS_API BOOL TESS_CALL TessBaseAPIProcessPages(TessBaseAPI* handle, const char* filename, const char* retry_config, int timeout_millisec, TessResultRenderer* renderer) { if (handle->ProcessPages(filename, retry_config, timeout_millisec, renderer)) return TRUE; else return FALSE; }
The last parameter of this function is TessResultRenderer. There is another cpp function for creating TessResultRenderer
TESS_API TessResultRenderer* TESS_CALL TessTextRendererCreate(const char* outputbase) { return new TessTextRenderer(outputbase); }
Now while calling this from my python, I did the following:
outputbase = "stdout" renderer = tesseract.TessTextRendererCreate(outputbase) text_out = tesseract.TessBaseAPIProcessPages(api, ctypes.create_string_buffer(path), None, 0, renderer) //Segmentation fault (core dumped) error on this line
but I keep getting Segmentation fault error.
My question is how can I called TessBaseAPIProcessPages from Python?
Some more reference links into the codebase:
referer api
Implementation of processPages(...)
Edit
After trying the commented suggestions, I did the following but I get an error: item 1 in _argtypes_ has no from_param method
PTessResultRenderer = ctypes.POINTER(TessResultRenderer) self.tesseract.TessTextRendererCreate.restype = PTessResultRenderer outputbase = "stdout" self.tesseract.TessTextRendererCreate.argtypes = [outputbase] #error here self.tesseract.TessTextRendererCreate ReturnVal = ctypes.c_bool self.tesseract.TessBaseAPIProcessPages.argtypes = [self.api, path, None, 0, PTessResultRenderer] self.tesseract.TessBaseAPIProcessPages.restype = ReturnVal self.tesseracto.TessBaseAPIProcessPages class TessResultRenderer(ctypes.Structure): pass
There is an example of using the tesseract C-API from ctypes in the contrib folder. However it seems to be a little out of date. contrib/tesseract-c_api-demo.py
You need to set the restype and argtypes for a few methods. Also, don't forget to call the init function on the handler. The following example works for me. It reads the text from a file called "test.bmp" in English into the text variable.
from ctypes import * from ctypes.util import find_library lang = b"eng" filename = b"test.bmp" TESSDATA_PREFIX = b"/usr/local/Cellar/tesseract/3.04.01_1/share/tessdata" path = find_library("libtesseract.dylib") tesseract = CDLL(path) class TessBaseAPI(Structure): pass class TessResultRenderer(Structure): pass tesseract.TessBaseAPICreate.restype = POINTER(TessBaseAPI) tesseract.TessBaseAPIInit3.argtypes = [POINTER(TessBaseAPI), c_char_p, c_char_p] tesseract.TessBaseAPIInit3.restype = c_bool tesseract.TessBaseAPIProcessPages.argtypes = [POINTER(TessBaseAPI), c_char_p, c_char_p, c_int, POINTER(TessResultRenderer)] tesseract.TessBaseAPIProcessPages.restype = c_bool tesseract.TessBaseAPIGetUTF8Text.argtypes = [POINTER(TessBaseAPI)] tesseract.TessBaseAPIGetUTF8Text.restype = c_char_p api = tesseract.TessBaseAPICreate() rc = tesseract.TessBaseAPIInit3(api, TESSDATA_PREFIX, lang); if (rc): tesseract.TessBaseAPIDelete(api) print("Could not initialize tesseract.\n") exit(3) success = tesseract.TessBaseAPIProcessPages(api, filename, None , 0, None) if success: text = tesseract.TessBaseAPIGetUTF8Text(api) print("="*78) print(text.decode("utf-8").strip()) print("="*78)
The output looks like this:
============================================================================== This is a lot of 12 point text to test the ocr code and see if it works on all types of file format. The quick brown dog jumped over the lazy fox. The quick brown dog jumped over the lazy fox. The quick brown dog jumped over the lazy fox. The quick brown dog jumped over the lazy fox. ==============================================================================
Edit: Replaced use of c_void_p with opaque types as suggested by eryksun. Thanks!
Segmentation faults occur when you run off of an array, or if you de-reference a null pointer. If you use a debugger, it will step you through all your code and show you exactly what is going on.
