帮我给每行代码加上注释 def letterbox(img, new_shape=(640, 640), color=(114, 114, 114), auto=True, scaleFill=False, scaleup=True): # 获取当前图片的长宽 shape = img.shape[:2] # current shape [height, width]) if isinstance(new_shape, int): new_shape = (new_shape, new_shape) r = min(new_shape[0] / shape[0], new_shape[1] / shape[1]) if not scaleup: r = min(r, 1.0) new_unpad = int(round(shape[1] * r)), int(round(shape[0] * r)) dw, dh = new_shape[1] - new_unpad[0], new_shape[0] - new_unpad[1] # wh padding if auto: dw, dh = np.mod(dw, 32), np.mod(dh, 32) # wh padding elif scaleFill: dw, dh = 0.0, 0.0 new_unpad = (new_shape[1], new_shape[0]) ratio = new_shape[1] / shape[1], new_shape[0] / shape[0] # width, height ratios dw /= 2 # divide padding into 2 sides dh /= 2 if shape[::-1] != new_unpad: img = cv2.resize(img, new_unpad, interpolation=cv2.INTER_LINEAR) top, bottom = int(round(dh - 0.1)), int(round(dh + 0.1)) left, right = int(round(dw - 0.1)), int(round(dw + 0.1)) img = cv2.copyMakeBorder(img, top, bottom, left, right, cv2.BORDER_CONSTANT, value=color) return img, ratio, (dw, dh)

# 定义一个函数，用于将图片转换为指定大小，并添加边框填充
def letterbox(img, new_shape=(640, 640), color=(114, 114, 114), auto=True, scaleFill=False, scaleup=True):
# 获取当前图片的长宽
shape = img.shape[:2] # current shape [height, width]

# 如果新的形状是一个整数，则将其转换为一个元组
if isinstance(new_shape, int):
new_shape = (new_shape, new_shape)

# 计算缩放比例
r = min(new_shape[0] / shape[0], new_shape[1] / shape[1])
if not scaleup:
r = min(r, 1.0)
new_unpad = int(round(shape[1] * r)), int(round(shape[0] * r))

# 计算填充的宽度和高度
dw, dh = new_shape[1] - new_unpad[0], new_shape[0] - new_unpad[1] # wh padding

# 如果自动填充则进行填充
if auto:
dw, dh = np.mod(dw, 32), np.mod(dh, 32) # wh padding
# 如果进行缩放填充，则进行填充
elif scaleFill:
dw, dh = 0.0, 0.0
new_unpad = (new_shape[1], new_shape[0])
ratio = new_shape[1] / shape[1], new_shape[0] / shape[0] # width, height ratios
dw /= 2 # divide padding into 2 sides
dh /= 2

# 如果当前形状不等于新的形状，则进行缩放和填充
if shape[::-1] != new_unpad:
img = cv2.resize(img, new_unpad, interpolation=cv2.INTER_LINEAR)
top, bottom = int(round(dh - 0.1)), int(round(dh + 0.1))
left, right = int(round(dw - 0.1)), int(round(dw + 0.1))
img = cv2.copyMakeBorder(img, top, bottom, left, right, cv2.BORDER_CONSTANT, value=color)

# 返回处理后的图片、缩放比例和填充宽度和高度
return img, ratio, (dw, dh)