python控制相机自动拍照_python控制gphoto2自动拍照
gphoto2驱动可以进行自动拍照，有一个命令行可以控制时间和次数。嗯，现在我们用python来编程控制，是不是更强大？
gphoto2 1.3.3
Python interface to libgphoto2
python-gphoto2 is a comprehensive Python interface (or binding) to libgphoto2. It is built using SWIG to automatically generate the interface code. This gives direct access to nearly all the libgphoto2 functions, but sometimes in a rather un-Pythonic manner.
Other Python bindings to libgphoto2 are available:piggyphoto uses ctypes (included in standard Python installations) to interface to the library. The gphoto2 source tree includes some Python bindings which also use ctypes.gphoto2-cffi uses cffi.
Contents
Python: http://python.org/ version 2.6 or greater (including Python 3)
SWIG: http://swig.org/ (optional since python-gphoto2 v0.11)
Note that you need the “development headers” versions of libgphoto2 and Python. Most Linux distributions’ package managers have these, but the names vary. Look for libgphoto2-2-dev or libgphoto2-devel or something similar.
There are several ways to install python-gphoto2, with varying levels of control over the installation process.
The commands below will install python-gphoto2 for your default Python version. To install for both Python 2 and Python 3, run the installation process twice with specific commands, i.e. pip2 and pip3 or python2 and python3.
Install with pip
The easiest installation method is to use the pip command:
sudo pip install -v gphoto2
Note that this may take longer than you expect as the SWIG generated files are compiled during installation. The -v option increases pip’s verbosity so you can see that it’s doing something.
Visit PyPI and download one of the zip or tar.gz files, then extract it and change to the new directory. For example:
tar xzf gphoto2-0.11.0.tar.gz
cd gphoto2-0.11.0
Python’s distutils are used to build and install python-gphoto2:
python setup.py build
sudo python setup.py install
Install from GitHub (SWIG required)
To install the very latest version, use git to “clone” the GitHub repository, then change to the new directory:
git clone https://github.com/jim-easterbrook/python-gphoto2.git
cd python-gphoto2
As before, Python’s distutils are used to build and install python-gphoto2, but now you have to run SWIG first to generate the files to be compiled:
python setup.py build_swig
python setup.py build
sudo python setup.py install
See “running SWIG” below for more detail.
Note
If you installed with pip the example files should be in /usr/share/python-gphoto2/examples or /usr/local/share/python-gphoto2/examples or somewhere similar. Otherwise they are in the examples sub-directory of your working directory.
Connect a digital camera to your computer, switch it on, and try one of the example programs:
python examples/camera-summary.py
If this works then you’re ready to start using python-gphoto2.
The Python interface to libgphoto2 should allow you to do anything you could do in a C program. However, the project is quite young and there are still bits missing and functions that cannot be called from Python. Let me know if you run into any problems.
The following paragraphs show how the Python interfaces differ from C. See the example programs for typical usage of the Python gphoto2 API.
Using SWIG to generate the Python interfaces automatically means that every function in libgphoto2 should be available to Python. The pydoc command can be used to show basic information about a function:
jim@firefly ~/python-gphoto2 $ pydoc gphoto2.gp_camera_folder_list_files
Help on built-in function gp_camera_folder_list_files in gphoto2:
gphoto2.gp_camera_folder_list_files = gp_camera_folder_list_files(...)
gp_camera_folder_list_files(camera, folder, context) -> int
Parameters:
camera: Camera *
folder: char const *
context: Context *
See also: gphoto2.Camera.folder_list_files
jim@firefly ~/python-gphoto2 $
If you compare this to the C API documentation of gp_camera_folder_list_files you will see that the C function signature includes an additional parameter “list” of type “CameraList *”. This is an “output” parameter, a concept that doesn’t really exist in Python. The Python version of gp_camera_folder_list_files returns a sequence containing the integer error code and the list value.
Most of the libgphoto2 functions that use pointer parameters to return values in the C API have been adapted like this in the Python API. (Unfortunately I’ve not found a way to persuade SWIG to include this extra return value in the documentation. You should use pydoc to check the parameters expected by the Python function.)
For example, the C code:
#include "gphoto2.h"int error;Camera *camera;error = gp_camera_new(&camera);...error = gp_camera_unref(camera);
has this Python equivalent:
import gphoto2 as gperror, camera = gp.gp_camera_new()...
Note that the gp_camera_unref() call is not needed (since python-gphoto2 version 0.5.0). It is called automatically when the python camera object is deleted.
Here is a complete example program (without any error checking):
import gphoto2 as gpcontext = gp.gp_context_new()error, camera = gp.gp_camera_new()error = gp.gp_camera_init(camera, context)error, text = gp.gp_camera_get_summary(camera, context)print('Summary')print('=======')print(text.text)error = gp.gp_camera_exit(camera, context)
SWIG has the ability to attach member functions to C structs such as the GPhoto2 Camera object. The Python interface includes many such member functions, allowing GPhoto2 to be used in a more “Pythonic” style. These member functions also include error checking. If an error occurs they raise a Python GPhoto2Error exception.
The example program can be re-written as follows:
import gphoto2 as gpcontext = gp.Context()camera = gp.Camera()camera.init(context)text = camera.get_summary(context)print('Summary')print('=======')print(str(text))camera.exit(context)
The member functions are more “hand crafted” than the rest of the Python bindings, which are automatically generated from the library header files. This means that there are some functions in the “C” interface that do not have corresponding member methods. Those that do include a “see also” reference in their docstring, as shown in the pydoc example above.
Most of the libgphoto2 functions return an integer to indicate success or failure. The Python interface includes a check_result() function to check these values and raise a GPhoto2Error exception if an error occurs.
This function also removes the error code from lists such as that returned by gp_camera_new() in the example. Using this function the earlier example becomes:
import gphoto2 as gpcontext = gp.gp_context_new()camera = gp.check_result(gp.gp_camera_new())gp.check_result(gp.gp_camera_init(camera, context))text = gp.check_result(gp.gp_camera_get_summary(camera, context))print('Summary')print('=======')print(text.text)gp.check_result(gp.gp_camera_exit(camera, context))
There may be some circumstances where you don’t want an exception to be raised when some errors occur. You can “fine tune” the behaviour of the check_result() function by adjusting the error_severity variable:
import gphoto2 as gpgp.error_severity[gp.GP_ERROR] = logging.WARNING...
In this case a warning message will be logged (using Python’s standard logging module) but no exception will be raised when a GP_ERROR error occurs. However, this is a “blanket” approach that treats all GP_ERROR errors the same. It is better to test for particular error conditions after particular operations, as described below.
The GPhoto2Error exception object has two attributes that may be useful in an exception handler.GPhoto2Error.code stores the integer error generated by the library function and GPhoto2Error.string stores the corresponding error message.
For example, to wait for a user to connect a camera you could do something like this:
import gphoto2 as gp...print('Please connect and switch on your camera')while True:
try:
camera.init(context)
except gp.GPhoto2Error as ex:
if ex.code == gp.GP_ERROR_MODEL_NOT_FOUND:
# no camera, try again in 2 seconds
time.sleep(2)
continue
# some other error we can't handle here
raise
# operation completed successfully so exit loop
break# continue with rest of program...
When just calling a single function like this, it’s probably easier to test the error value directly instead of using Python exceptions:
import gphoto2 as gp...print('Please connect and switch on your camera')while True:
error = gp.gp_camera_init(camera, context)
if error >= gp.GP_OK:
# operation completed successfully so exit loop
break
if error != gp.GP_ERROR_MODEL_NOT_FOUND:
# some other error we can't handle here
raise gp.GPhoto2Error(error)
# no camera, try again in 2 seconds
time.sleep(2)# continue with rest of program...
The libgphoto2 library includes functions (such as gp_log()) to output messages from its various functions. These messages are mostly used for debugging purposes, and it can be helpful to see them when using libgphoto2 from Python. The Python interface includes a use_python_logging() function to connect libgphoto2 logging to the standard Python logging system. You should call use_python_logging() near the start of your program, as shown in the examples.
The libgphoto2 logging messages have four possible severity levels, each of which is mapped to a suitable Python logging severity. You can override this mapping by passing your own to use_python_logging():
import loggingimport gphoto2 as gp...gp.use_python_logging(mapping={
gp.GP_LOG_ERROR : logging.INFO,
gp.GP_LOG_VERBOSE : logging.DEBUG,
gp.GP_LOG_DEBUG : logging.DEBUG - 3,
gp.GP_LOG_DATA : logging.DEBUG - 6})...
If you prefer to use your own logging system you can define a logging callback function in Python. The function must take 3 parameters: level, domain and string. Since python-gphoto2 version 1.3 the callback function is installed with gp_log_add_func:
import gphoto2 as gp...def callback(level, domain, string):
print('Callback: level =', level, ', domain =', domain, ', string =', string)...callback_id = gp.check_result(gp.gp_log_add_func(gp.GP_LOG_VERBOSE, callback))...
Note that since python-gphoto2 version 1.3.2 gp_log_add_func takes two parameters: the logging level and your callback function.gp_log_add_func returns an AugmentedInt value that stores a reference to your callback function along with the function’s return value. It can be passed to gp_log_remove_func to uninstall your callback.
Earlier versions of python-gphoto2 used gp_log_add_func_py to install the callback:
import gphoto2 as gp...def callback(level, domain, string):
print('Callback: level =', level, ', domain =', domain, ', string =', string)...callback_id = gp.check_result(gp.gp_log_add_func_py(gp.GP_LOG_VERBOSE, callback))...
In this case a reference to your callback function is stored by the SWIG interface.
Since python-gphoto2 version 1.2.0 these functions return a FileData object that supports the buffer protocol. The data can be made accessible to Python (2.7 and 3.x) by using a memoryview object. This allows the data to be used without copying. See the copy-data.py example for typical usage.
In earlier versions of python-gphoto2 these functions returned a str (Python 2) or bytes (Python 3) object containing a copy of the data in the CameraFile object.
Although the documentation says the buf parameter is of type char * you can pass any Python object that exposes a writeable buffer interface. This allows you to read a file directly into a Python object without additional copying. See the copy-chunks.py example which uses memoryview to expose a bytearray.
These functions return both the event type and the event data. The data you get depends on the type.GP_EVENT_FILE_ADDED and GP_EVENT_FOLDER_ADDED events return a CameraFilePath, others return None.
Running SWIG
SWIG is used to convert the .i interface definition files in src/gphoto2 to .py and .c files. These are then compiled to build the Python interface to libgphoto2. The files downloaded from PyPI include the SWIG generated files, but you may wish to regenerate them by running SWIG again (e.g. to test a new version of SWIG or of libgphoto2). You will also need to run SWIG if you have downloaded the python-gphoto2 sources from GitHub instead of using PyPI.
The file setup.py defines an extra command to run SWIG. It has no user options:
python setup.py build_swig
By default this builds the interface for the version of libgphoto2 installed on your computer. The interface files are created in directories with names like src/swig-bi-gp2.5-py3. This naming scheme allows for different versions of Python and libgphoto2, and use (or not) of the SWIG -builtin flag. The appropriate version is chosen when the interface is built.
To build interfaces for additional versions of libgphoto2 (e.g. v2.4 as well as v2.5) you need to put a copy of that version’s include (.h) files in a sub-directory of your working directory called include/gphoto2-2.x and then run setup.py build_swig again.
python-gphoto2 - Python interface to libgphoto2http://github.com/jim-easterbrook/python-gphoto2Copyright (C) 2014-15 Jim Easterbrook jim@jim-easterbrook.me.uk
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.
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