Rgb to grayscale

The camera displays color images in real time, and saving the color images as pgm format images is convenient for face recognition
This is my codes:

Hello World Example

Welcome to the OpenMV IDE! Click on the green run arrow button below to run the script!

import sensor, image, time

sensor.reset() # Reset and initialize the sensor.
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QVGA) # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000) # Wait for settings take effect.
clock = time.clock() # Create a clock object to track the FPS.

clock.tick() # Update the FPS clock.
img = sensor.snapshot() # Take a picture and return the image.
img2=img.to_grayscale([copy=False[, rgb_channel=-1]])

print(clock.fps())              # Note: OpenMV Cam runs about half as fast when connected
break                                # to the IDE. The FPS should increase once disconnected.