Python opencv resize图片并保存原有的图像比例

def resize_img_keep_ratio(img_name,target_size):
    img = cv2.imread(img_name)
    old_size= img.shape[0:2]
    #ratio = min(float(target_size)/(old_size))
    ratio = min(float(target_size[i])/(old_size[i]) for i in range(len(old_size)))
    new_size = tuple([int(i*ratio) for i in old_size])
    img = cv2.resize(img,(new_size[1], new_size[0]))
    pad_w = target_size[1] - new_size[1]
    pad_h = target_size[0] - new_size[0]
    top,bottom = pad_h//2, pad_h-(pad_h//2)
    left,right = pad_w//2, pad_w -(pad_w//2)
    img_new = cv2.copyMakeBorder(img,top,bottom,left,right,cv2.BORDER_CONSTANT,None,(0,0,0))
    return img_new
if__name__==‘main‘:
    img = ‘‘
    target_size=[448,112]
    resize_img_keep_ratio()