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digitalmars.D - OpenCV bindings for D

reply wobbles <grogan.colin gmail.com> writes:
Hi Folks,

I have a project in mind that I'd like to run on my new Raspberry 
Pi 3.
Essentially a security camera that will only record when it 
detects changes between frames.
Now, this is already a solved problem I believe, however in the 
interest of learning I want to do it myself.

Ideally, I'd compare two images using the OpenCV library, and 
ideally I'd do that from D code.

However, there exists no OpenCV binding for D that I can find. Is 
there a technical reason for this?

I understand the OpenCV C api is quite old and dated, and it's 
recommended to use the C++ one as a result.
On that, where is C++ / D linkage at?

I know very little about linking the two, but it's something I'd 
like to learn more about and see this as an opportunity for that 
- before I sink a load of time into it, however, it'd be good to 
know if it's even feasibly possible to do so.

Thanks!
Mar 21 2016
next sibling parent reply Guillaume Piolat <contact gam3sfrommars.fr> writes:
On Monday, 21 March 2016 at 15:45:36 UTC, wobbles wrote:
 Hi Folks,

 I have a project in mind that I'd like to run on my new 
 Raspberry Pi 3.
 Essentially a security camera that will only record when it 
 detects changes between frames.
 Now, this is already a solved problem I believe, however in the 
 interest of learning I want to do it myself.

 Ideally, I'd compare two images using the OpenCV library, and 
 ideally I'd do that from D code.

 However, there exists no OpenCV binding for D that I can find. 
 Is there a technical reason for this?

 I understand the OpenCV C api is quite old and dated, and it's 
 recommended to use the C++ one as a result.
 On that, where is C++ / D linkage at?

 I know very little about linking the two, but it's something 
 I'd like to learn more about and see this as an opportunity for 
 that - before I sink a load of time into it, however, it'd be 
 good to know if it's even feasibly possible to do so.

 Thanks!
It's quite easy to write bindings for libraries that have a C interface (ie most), if only a bit boring. - First check in code.dlang.org or https://github.com/D-Programming-Deimos it doesn't not already exist. - Choose to create a static or dynamic bindings. For multiplatform a dynamic loader will be easier dependency-wise, for *nix systems static linking may be easier. - When porting C headers, there is a few gotchas: https://p0nce.github.io/d-idioms/#Porting-from-C-gotchas - Take inspiraton at either Deimos or Derelict to create either.
Mar 21 2016
parent reply wobbles <grogan.colin gmail.com> writes:
On Monday, 21 March 2016 at 16:01:59 UTC, Guillaume Piolat wrote:
 On Monday, 21 March 2016 at 15:45:36 UTC, wobbles wrote:
 Hi Folks,

 I have a project in mind that I'd like to run on my new 
 Raspberry Pi 3.
 Essentially a security camera that will only record when it 
 detects changes between frames.
 Now, this is already a solved problem I believe, however in 
 the interest of learning I want to do it myself.

 Ideally, I'd compare two images using the OpenCV library, and 
 ideally I'd do that from D code.

 However, there exists no OpenCV binding for D that I can find. 
 Is there a technical reason for this?

 I understand the OpenCV C api is quite old and dated, and it's 
 recommended to use the C++ one as a result.
 On that, where is C++ / D linkage at?

 I know very little about linking the two, but it's something 
 I'd like to learn more about and see this as an opportunity 
 for that - before I sink a load of time into it, however, it'd 
 be good to know if it's even feasibly possible to do so.

 Thanks!
It's quite easy to write bindings for libraries that have a C interface (ie most), if only a bit boring.
That's the thing, it doesn't have a C interface (or more correctly, it's modern versions don't have a C interface as it has been deprecated since I think version 2.4. OpenCV is at 3.4 now). I was wondering if there was any difficulties interfacing D to the C++ API?
Mar 21 2016
parent poliklosio <poliklosio happypizza.com> writes:
On Monday, 21 March 2016 at 19:16:16 UTC, wobbles wrote:
 On Monday, 21 March 2016 at 16:01:59 UTC, Guillaume Piolat 
 wrote:
 On Monday, 21 March 2016 at 15:45:36 UTC, wobbles wrote:
 Hi Folks,

 I have a project in mind that I'd like to run on my new 
 Raspberry Pi 3.
 Essentially a security camera that will only record when it 
 detects changes between frames.
 Now, this is already a solved problem I believe, however in 
 the interest of learning I want to do it myself.

 Ideally, I'd compare two images using the OpenCV library, and 
 ideally I'd do that from D code.

 However, there exists no OpenCV binding for D that I can 
 find. Is there a technical reason for this?

 I understand the OpenCV C api is quite old and dated, and 
 it's recommended to use the C++ one as a result.
 On that, where is C++ / D linkage at?

 I know very little about linking the two, but it's something 
 I'd like to learn more about and see this as an opportunity 
 for that - before I sink a load of time into it, however, 
 it'd be good to know if it's even feasibly possible to do so.

 Thanks!
It's quite easy to write bindings for libraries that have a C interface (ie most), if only a bit boring.
That's the thing, it doesn't have a C interface (or more correctly, it's modern versions don't have a C interface as it has been deprecated since I think version 2.4. OpenCV is at 3.4 now). I was wondering if there was any difficulties interfacing D to the C++ API?
I don't have much experience with D, but I have with OpenCV. The key class in OpenCV is cv::Mat, which is used to represent images as arguments and return values of almost every OpenCV algorithm. It is kind of a handle class - it optionally owns image data and manages its lifetime through reference counting and RAII. The sheer number of constructors is a bit overwhelming. See http://docs.opencv.org/2.4/modules/core/doc/basic_structures.html#mat-mat I would be interested to see what D experts would say about interfacing such class. My guess would be that you may have trouble exposing this directly to the D side in a useful way. You may have to write some helpers or even a wrapper on the C++ side.
Mar 21 2016
prev sibling parent Suliman <evermind live.ru> writes:
Try to look at https://github.com/ljubobratovicrelja/dcv
Mar 21 2016