在调用opencv的imread(filename, flags=None)函数时，后面有个flags=None参数，但打开文档轻描淡写，不知该参数上哪找去，用全局搜索也搜不到，莫非要到官网查？（擦汗’’）
打开官网，有个Online documentation，点它:
然后找到自己opencv版本点进去，我的是这个（如果不知道自己opencv版本可以在控制台执行pip list查看）：
点进去后右上角搜索就ok了：
IMREAD_UNCHANGED Python: cv.IMREAD_UNCHANGEDIf set, return the loaded image as is (with alpha channel, otherwise it gets cropped).IMREAD_GRAYSCALE Python: cv.IMREAD_GRAYSCALEIf set, always convert image to the single channel grayscale image (codec internal conversion).IMREAD_COLOR Python: cv.IMREAD_COLORIf set, always convert image to the 3 channel BGR color image.IMREAD_ANYDEPTH Python: cv.IMREAD_ANYDEPTHIf set, return 16-bit/32-bit image when the input has the corresponding depth, otherwise convert it to 8-bit.IMREAD_ANYCOLOR Python: cv.IMREAD_ANYCOLORIf set, the image is read in any possible color format.IMREAD_LOAD_GDAL Python: cv.IMREAD_LOAD_GDALIf set, use the gdal driver for loading the image.IMREAD_REDUCED_GRAYSCALE_2 Python: cv.IMREAD_REDUCED_GRAYSCALE_2If set, always convert image to the single channel grayscale image and the image size reduced 1/2.IMREAD_REDUCED_COLOR_2 Python: cv.IMREAD_REDUCED_COLOR_2If set, always convert image to the 3 channel BGR color image and the image size reduced 1/2.IMREAD_REDUCED_GRAYSCALE_4 Python: cv.IMREAD_REDUCED_GRAYSCALE_4If set, always convert image to the single channel grayscale image and the image size reduced 1/4.IMREAD_REDUCED_COLOR_4 Python: cv.IMREAD_REDUCED_COLOR_4If set, always convert image to the 3 channel BGR color image and the image size reduced 1/4.IMREAD_REDUCED_GRAYSCALE_8 Python: cv.IMREAD_REDUCED_GRAYSCALE_8If set, always convert image to the single channel grayscale image and the image size reduced 1/8.IMREAD_REDUCED_COLOR_8 Python: cv.IMREAD_REDUCED_COLOR_8If set, always convert image to the 3 channel BGR color image and the image size reduced 1/8.IMREAD_IGNORE_ORIENTATION Python: cv.IMREAD_IGNORE_ORIENTATIONIf set, do not rotate the image according to EXIF's orientation flag.
参考文章：python opencv imread()函数 （从文件加载图像）
