Hello all,
FFI was *a little *complexer than I had thought. And the Tesseract api was
not helping either. But now I think I'm getting closer to make the example
Ben proposed (https://github.com/tesseract-ocr/tesseract/wiki/APIExample,
the C-program using the C-API) work in Squeak.
Just one thing I cannot find an example for. I have to create the
ExternalStructure classes for the structures PIXMAP and RGBA_QUAD.
RGBA_QUAD is easy, but the PIXMAP-structure starts with an array of
RGBA_QUADs. RGBA_QUAD[] does not seem to be working as a type
specification, and RGBA_SQUAD* will reserve place for the first element,
but not the whole array. Is there an example for such structures?
From the Header file:
00101 <https://tpgit.github.io/Leptonica/struct_pix_colormap.html>
struct PixColormap
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html>00102
{00103 <https://tpgit.github.io/Leptonica/struct_pix_colormap.html#a2a14164dbec38ebab11eee1bea569cbc>
void *array
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html#a2a14164dbec38ebab11eee1bea569cbc>;
/* colormap table (array of RGBA_QUAD) */00104
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html#ac40f93eac5fc385f43e17d0b537e40e2>
l_int32 <https://tpgit.github.io/Leptonica/environ_8h.html#a9085c7874153c280a4171244aa052e4e>
depth <https://tpgit.github.io/Leptonica/struct_pix_colormap.html#ac40f93eac5fc385f43e17d0b537e40e2>;
/* of pix (1, 2, 4 or 8 bpp) */00105
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html#ad4398c00071558f7821c82c897548fa8>
l_int32 <https://tpgit.github.io/Leptonica/environ_8h.html#a9085c7874153c280a4171244aa052e4e>
nalloc
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html#ad4398c00071558f7821c82c897548fa8>;
/* number of color entries allocated */00106
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html#a99005f6c729d84e55143a208b61f99bf>
l_int32 <https://tpgit.github.io/Leptonica/environ_8h.html#a9085c7874153c280a4171244aa052e4e>
n <https://tpgit.github.io/Leptonica/struct_pix_colormap.html#a99005f6c729d84e55143a208b61f99bf>;
/* number of color entries used */00107 };00108
<https://tpgit.github.io/Leptonica/pix_8h.html#ab2fccb09f9188d3e2cc90f8df11b7de7>
typedef struct PixColormap
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html> PIXCMAP
<https://tpgit.github.io/Leptonica/struct_pix_colormap.html>;00109
00110 00111 /* Colormap table entry (after the BMP version).00112
* Note that the BMP format stores the colormap table exactly00113
* as it appears here, with color samples being stored
sequentially,00114 * in the order (b,g,r,a). */00115
<https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html> struct
RGBA_Quad <https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html>00116
{00117 <https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a57ceb621e5e83bc2d8b9d78cc426cefd>
l_uint8 <https://tpgit.github.io/Leptonica/environ_8h.html#a7ed60554e7d6dd89aca643189b1e70ad>
blue <https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a57ceb621e5e83bc2d8b9d78cc426cefd>;00118
<https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a32f8a3f2225995fcedfb6d80bb480c05>
l_uint8 <https://tpgit.github.io/Leptonica/environ_8h.html#a7ed60554e7d6dd89aca643189b1e70ad>
green <https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a32f8a3f2225995fcedfb6d80bb480c05>;00119
<https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a9ad88fbc3a671fbe8406e608b59563fa>
l_uint8 <https://tpgit.github.io/Leptonica/environ_8h.html#a7ed60554e7d6dd89aca643189b1e70ad>
red <https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a9ad88fbc3a671fbe8406e608b59563fa>;00120
<https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a0811097c12e668433c357edcb973da76>
l_uint8 <https://tpgit.github.io/Leptonica/environ_8h.html#a7ed60554e7d6dd89aca643189b1e70ad>
reserved <https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html#a0811097c12e668433c357edcb973da76>;00121
};00122 <https://tpgit.github.io/Leptonica/pix_8h.html#ac4b7ee5b0e033dd9df33e464059cdf87>
typedef struct RGBA_Quad
<https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html>
RGBA_QUAD <https://tpgit.github.io/Leptonica/struct_r_g_b_a___quad.html>;
Post by Kjell GodoCan i just write a simple C shared library or DLL which calls the C++ ? So
you are repackaging the C++ as a C library? I canât see how this tack could
fail to work. Just repackage C++ as C.
You would have to come up with a procedural less OOP-ish API i guess. You
could have C API functions F which take an Object as Fâs first input and in
this way each C++ Method becomes a C function. You only need wrap as much
of the C++ API as you want to use and each C function just calls its C++
Method so making the wrappers is highly simple and mechanical i should
think. it could even be automated. But i know some C++ but have never made
anything in it.
I suppose that if Smalltalk cannot contain a C++ Object then you could
make a C struct which can be in Smalltalk and you have the API function
copy this struct into the C++ Object then act on it then copy the Object
data back into the struct which is in Smalltalk. But thatâs a lot of work.
Surely you can have a pointer to a C++ Object in Smalltalk.
Maybe it would be better to have a separate C++ program P that you
communicate with by sockets using Object handles H which are just Integer
Array indexes into an Array of Objects in P? i suppose there could be a
shared lib L that FFI could call which could call back program P if sockets
were too slow or something.
I guess Dolphin can input a Smalltalk BlockClosure B into an FFI call to
L which could input B into program P which could call B to get back into
Dolphin but i havenât tried it myself.
I guess there is a Smalltalk interface to Python via a socket and then
from Python to C++ is easy? Seems like a code generator that has all this
stuff figured out could be good. I think VisualWorks is probably good at
connecting to C++ via FFI. What about chicken scheme or any of the C based
Schemes? What about Smalltalk/X?
borgLisp is an idea to make multiple Lisp dialects each isomorphic to its
target language like C or C++ or Python or Ruby or Prolog or java or C# or
Scheme or Rust etc any language can have an isomorphic Lisp dialect
targeting it in order to bind all the languages into a single borgLisp
where you can mix and match all the languages together. Where each Lisp
dialect is just a simple Lisp code generator. And so once all the languages
are in Lisp then all the Lisp things can be used to mix and match all the
languages together and using Nix to set up and configure everything so
everything works together one click like. all the different languages. so
they can all work together in an easy generative format. So every language
becomes Lisp and Lisp becomes every language. Using code generation you
could even make a Debugger in Lisp and Smalltalk which could source debug
any language like the Smalltalk debugger does for Smalltalk.
but i guess this is off the topic
Post by Ben ComanPost by Edwin AncaerHello list,
As I'm looking at a way to automate the search of documents in my humble
administration, I read some articles about OCR. I came along an article
about using Python with Tesseract, to transform an scan of a document into
text, that is searchable.
My question now is if I can do something similar with Squeak. To my
inexperienced eye, it seems like I should use FFI to call the functions in
the Tesseract API, but this API is in C++, and I don't know if it is
possible to use FFI to call C++ functions?
You are right C++ is difficult because of the name mangling of function
symbols,
but good fortune I notice Tesseract has C bindings...
https://github.com/tesseract-ocr/tesseract#for-developers
https://github.com/tesseract-ocr/tesseract/blob/master/src/api/capi.h
so it looks like you are in the clear.
Or should I forget the API and use OSProcess to start the tesseract
FFI will be more flexible.
Could anyone point me in the right direction, or just tell if the whole
I think its a great idea and actually Tesseract FFI is something I've
wanted to play with before but not had the time.
I'd be interested to hear how you go with it.
cheers -ben
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