一：改变颜色
cv2.cvtColor（），cv2.inRange（）
一般BGR转Gray，BGR转HSV
cv2.cvtColor(input_image,flag) flag: cv2.COLOR_BGR2GRAY cv2.COLOR_BGR2HSV
(1) 追踪颜色：颜色
HSV: 色调（H），饱和度（S），明度（V）.
Hue range is [0,179], Saturation range is [0,255] and Value range is [0,255].
(2) 从BGR得到HSV的值
二：图像的几何变换
cv2.getPerspectiveTransform
（1）转换：cv2.warpAffine ：2x3 transformation matrix
cv2.warpPerspective：3x3 transformation matrix
（2）缩放 cv2.resize(). 差值方法：cv2.INTER_AREA，cv2.INTER_CUBIC，cv2.INTER_LINEAR
（3）移动 ： 移动tx，ty
（4）旋转：旋转90度
三：Image Thresholding
（1）简单的阈值
cv2.THRESH_BINARY
cv2.THRESH_BINARY_INV
cv2.THRESH_TRUNC
cv2.THRESH_TOZERO
cv2.THRESH_TOZERO_INV
Result:
（2）可适应的阈值
cv2.ADAPTIVE_THRESH_MEAN_C : threshold value is the mean of neighbourhood area.
cv2.ADAPTIVE_THRESH_GAUSSIAN_C : threshold value is the weighted sum of neighbourhood values where weights are a gaussian window.
Results:
