问题描述
我正在尝试使用pyueye库运行ML相机,并且遇到ctypes问题。一个函数需要一个'ctypes instance'类型的参数,尽管尝试了所有可能的变体,但我仍无法弄清楚如何使用ctypes库生成该参数。该库没有有关python的文档,但是我要使用的函数的C文档是:
Syntax
INT is_SetAutoparameter (HIDS hCam,INT param,double* pval1,double* pval2)
Example 1
//Enable auto gain control:
double dEnable = 1;
int ret = is_SetAutoparameter (hCam,IS_SET_ENABLE_AUTO_GAIN,&dEnable,0);
nRet = ueye.is_SetAutoparameter(hCam,ueye.IS_SET_ENABLE_AUTO_GAIN,ctypes.byref(ctypes.c_long(1)),ctypes.byref(ctypes.c_long(0)))
Error:
ret = _is_SetAutoparameter(_hCam,_param,ctypes.byref(pval1),ctypes.byref(pval2))
TypeError: byref() argument must be a ctypes instance,not 'CArgObject'
关于ctypes实例的任何建议吗?谢谢
编辑:最小的可复制示例
from pyueye import ueye
import ctypes
class Turfcam:
def main(self):
turfcam.take_photo()
def take_photo(self):
hCam = ueye.HIDS(0)
pval1 = ctypes.c_double(1)
pval2 = ctypes.c_double(0)
nRet = ueye.is_SetAutoparameter(hCam,ctypes.byref(pval2))
# Camera Init
nRet = ueye.is_InitCamera(hCam,None)
if __name__ == "__main__":
turfcam = Turfcam()
turfcam.main()
解决方法
pyueye
库仅提供一些基本文档:
_is_SetAutoParameter = _bind("is_SetAutoParameter",[ctypes.c_uint,ctypes.c_int,ctypes.POINTER(ctypes.c_double),ctypes.POINTER(ctypes.c_double)],ctypes.c_int)
def is_SetAutoParameter(hCam,param,pval1,pval2):
"""
:param hCam: c_uint (aka c-type: HIDS)
:param param: c_int (aka c-type: INT)
:param pval1: c_double (aka c-type: double \*)
:param pval2: c_double (aka c-type: double \*)
:returns: success,or no success,that is the answer
:raises NotImplementedError: if function could not be loaded
"""
if _is_SetAutoParameter is None:
raise NotImplementedError()
_hCam = _value_cast(hCam,ctypes.c_uint)
_param = _value_cast(param,ctypes.c_int)
ret = _is_SetAutoParameter(_hCam,_param,ctypes.byref(pval1),ctypes.byref(pval2))
return ret
包装程序正在执行byref
,因此仅需要传递ctypes
对象。 uEye docs说参数可以是输入或输出参数,因此请始终创建c_double
对象并根据传递的函数的需要对其进行初始化。请注意,对于输出参数,您必须为对象分配一个名称,以便该对象在要查询的调用之后存在。通过直接将ctypes.c_double(value)
传递给函数可以避免输入参数,但是为了保持一致,我总是为对象分配名称:
示例:
pval1 = ctypes.c_double()
pval2 = ctypes.c_double() # not used for output on IS_GET_ENABLE_AUTO_GAIN
nRet = ueye.is_SetAutoParameter(hCam,ueye.IS_GET_ENABLE_AUTO_GAIN,pval2)
print(pval1.value) # query the returned value