# Single Color RGB565 Blob Tracking Example
#
# This example shows off single color RGB565 tracking using the OpenMV Cam.
import sensor, image, time, math
threshold_index = 0 # 0 for red, 1 for green, 2 for blue
# Color Tracking Thresholds (L Min, L Max, A Min, A Max, B Min, B Max)
# The below thresholds track in general red/green/blue things. You may wish to tune them...
thresholds = [(67, 82, -128, 127, 28, 127)] # generic_red_thresholds 阈值设置，代表LAB的最大值和最小值
sensor.reset() #重置感光元件/重置摄像机
sensor.set_pixformat(sensor.RGB565) #设置模式为彩图
sensor.set_framesize(sensor.QVGA) #设置图像大小为QVGA
sensor.skip_frames(time = 2000) #使以上操作生效
sensor.set_auto_gain(False) # must be turned off for color tracking 关闭颜色增益
sensor.set_auto_whitebal(False) # must be turned off for color tracking 关闭白平衡
clock = time.clock()
# Only blobs that with more pixels than "pixel_threshold" and more area than "area_threshold" are
# returned by "find_blobs" below. Change "pixels_threshold" and "area_threshold" if you change the
# camera resolution. "merge=True" merges all overlapping blobs in the image.
while(True):
clock.tick() #开始追踪运行时间
img = sensor.snapshot() #在感光元件截取一张图
for blob in img.find_blobs([thresholds[threshold_index]], pixels_threshold=320, area_threshold=400, merge=True):
#img.find_blobs()函数创建一个class image.blob对象，返回一个包含多个元素的字典
# These values depend on the blob not being circular - otherwise they will be shaky.
if blob.elongation() > 0.5: #返回一个介于0和1之间的值，该值表示对象的长度（不是圆形）。一条线将是1。
img.draw_edges(blob.min_corners(), color=(255,0,0))
img.draw_line(blob.major_axis_line(), color=(0,255,0))
img.draw_line(blob.minor_axis_line(), color=(0,0,255))
# These values are stable all the time.
img.draw_rectangle(blob.rect()) #识别到颜色则画框框起
img.draw_cross(blob.cx (), blob.cy()) #识别到颜色则画十字
# Note - the blob rotation is unique to 0-180 only.
img.draw_keypoints([(blob.cx(), blob.cy(), int(math.degrees(blob.rotation())))], size=20)
print(blob)
# print(clock.fps())#停止追踪运行时间，并返回当前帧数