小车巡线，theta角怎么获得？

[会飞的哈哈猫]

# Fast Linear Regression Example
#
# This example shows off how to use the get_regression() method on your OpenMV Cam
# to get the linear regression of a ROI. Using this method you can easily build
# a robot which can track lines which all point in the same general direction
# but are not actually connected. Use find_blobs() on lines that are nicely
# connected for better filtering options and control.
#
# This is called the fast linear regression because we use the least-squares
# method to fit the line. However, this method is NOT GOOD FOR ANY images that
# have a lot (or really any) outlier points which corrupt the line fit...

#设置阈值，（0，100）检测黑色线
THRESHOLD = (0, 100) # Grayscale threshold for dark things...

#设置是否使用img.binary()函数进行图像分割
BINARY_VISIBLE = True # Does binary first so you can see what the linear regression
                      # is being run on... might lower FPS though.

import sensor, image, time

sensor.reset()
sensor.set_pixformat(sensor.GRAYSCALE)
sensor.set_framesize(sensor.QQVGA)
sensor.skip_frames(time = 2000)
clock = time.clock()

while(True):
    clock.tick()
    img = sensor.snapshot().binary([THRESHOLD]) if BINARY_VISIBLE else sensor.snapshot()

    # Returns a line object similar to line objects returned by find_lines() and
    # find_line_segments(). You have x1(), y1(), x2(), y2(), length(),
    # theta() (rotation in degrees), rho(), and magnitude().
    #
    # magnitude() represents how well the linear regression worked. It goes from
    # (0, INF] where 0 is returned for a circle. The more linear the
    # scene is the higher the magnitude.
    #函数返回回归后的线段对象line，有x1(), y1(), x2(), y2(), length(), theta(), rho(), magnitude()参数。
    #x1 y1 x2 y2分别代表线段的两个顶点坐标，length是线段长度，theta是线段的角度。
    #magnitude表示线性回归的效果，它是（0，+∞）范围内的一个数字，其中0代表一个圆。如果场景线性回归的越好，这个值越大。
    line = img.get_regression([(255,255) if BINARY_VISIBLE else THRESHOLD])

    if (line): img.draw_line(line.line(), color = 127)
    print("FPS %f, mag = %s" % (clock.fps(), str(line.magnitude()) if (line) else "N/A"))

# About negative rho values:
#
# A [theta+0:-rho] tuple is the same as [theta+180:+rho].
这个例程里，怎么获得直线的theta角，这个算法的思想是什么啊 ？新手求教，万分感谢

[yuan]

theta角就是最后的画出来的line的角度，可以通过查阅中文文档来获取。
line-中文文档

get_regression函数就是对视野内的直线进行拟合，快速线性回归，得到一条最合适的线，控制小车（或飞控）追踪这条线，来达到巡线的目的。

具体请参考：

• 例程讲解-09-linear_regression_fast 快速线性回归（巡线）

• image.get_regression 中文文档