calculate_lines_gauss_parameters (MaxLineWidth, [Contrast,0], Sigma, Low, High)
输入最大线宽以及对比度计算Sigma,Low,High
* Check control parameters
if (|MaxLineWidth| != 1)
throw ('Wrong number of values of control parameter: 1')
endif
if (not is_number(MaxLineWidth))
throw ('Wrong type of control parameter: 1')
endif
if (MaxLineWidth <= 0)
throw ('Wrong value of control parameter: 1')
endif
if (|Contrast| != 1 and |Contrast| != 2)
throw ('Wrong number of values of control parameter: 2')
endif
if (min(is_number(Contrast)) == 0)
throw ('Wrong type of control parameter: 2')
endif
* Set and check ContrastHigh
ContrastHigh := Contrast[0]
if (ContrastHigh < 0)
throw ('Wrong value of control parameter: 2')
endif
* Set or derive ContrastLow
if (|Contrast| == 2)
ContrastLow := Contrast[1]
else
ContrastLow := ContrastHigh / 3.0
endif
* Check ContrastLow
if (ContrastLow < 0)
throw ('Wrong value of control parameter: 2')
endif
if (ContrastLow > ContrastHigh)
throw ('Wrong value of control parameter: 2')
endif
*
* Calculate the parameters Sigma, Low, and High for lines_gauss
if (MaxLineWidth < sqrt(3.0))* 注意LineWidthMax < sqrt(3.0)将导致Sigma < 0.5，这没有任何意义，因为相应的平滑滤波掩码的大小为1x1。
* 为了避免这种情况，LineWidthMax被限制为大于或等于sqrt(3.0)的值，而对比度值则适用于反映这样一个事实:
* 在平滑图像中，比sqrt(3.0)像素更细的线具有更低的对比度(与宽为sqrt(3.0)像素的线相比)。
ContrastLow := ContrastLow * MaxLineWidth / sqrt(3.0)
ContrastHigh := ContrastHigh * MaxLineWidth / sqrt(3.0)
MaxLineWidth := sqrt(3.0)
endif
* 将LineWidthMax和给定的对比值转换为lines_gauss所需的输入参数Sigma, Low和High
HalfWidth := MaxLineWidth / 2.0
Sigma := HalfWidth / sqrt(3.0)
Help := -2.0 * HalfWidth / (sqrt(6.283185307178) * pow(Sigma,3.0)) * exp(-0.5 * pow(HalfWidth / Sigma,2.0))
High := fabs(ContrastHigh * Help)
Low := fabs(ContrastLow * Help)
return ()
