www.digitalmars.com         C & C++   DMDScript  

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 next sibling parent Suliman <evermind live.ru> writes:
Try to look at https://github.com/ljubobratovicrelja/dcv
Mar 21 2016
prev sibling parent Ferhat =?UTF-8?B?S3VydHVsbXXFnw==?= <aferust gmail.com> 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.

 [...]


this is now on: https://github.com/aferust/opencvd
Apr 04 2019