修改：
1.多张图片放入/data/demo/文件夹中（无需在demo.py中列出图片的名字）
2.将识别的图片结果保存到其他文件夹中（这里是在主目录下建了testfigs文件夹）

#!/usr/bin/env python

# --------------------------------------------------------
# Tensorflow Faster R-CNN
# Licensed under The MIT License [see LICENSE for details]
# Written by Xinlei Chen, based on code from Ross Girshick
# --------------------------------------------------------

"""
Demo script showing detections in sample images.

See README.md for installation instructions before running.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import matplotlib    
matplotlib.use('Agg')  

import _init_paths
from model.config import cfg
from model.test import im_detect
from model.nms_wrapper import nms

from utils.timer import Timer
import tensorflow as tf
import matplotlib.pyplot as plt
import numpy as np
import os, cv2
import argparse

from nets.vgg16 import vgg16
from nets.resnet_v1 import resnetv1

CLASSES = ('__background__',  # always index 0
            '类别1',
            '类别2',
            '类别3',
            '类别4')

NETS = {'vgg16': ('vgg16_faster_rcnn_iter_5000.ckpt',),'res50': ('res50_faster_rcnn_iter_5000.ckpt',),'res101': ('res101_faster_rcnn_iter_5000.ckpt',),'res152': ('res152_faster_rcnn_iter_5000.ckpt',)}
DATASETS= {'pascal_voc': ('voc_2007_trainval',),'pascal_voc_0712': ('voc_2007_trainval+voc_2012_trainval',)}

def vis_detections(im, class_name, dets, thresh=0.5):
    """Draw detected bounding boxes."""
    inds = np.where(dets[:, -1] >= thresh)[0]
    if len(inds) == 0:
        return

    im = im[:, :, (2, 1, 0)]
    fig, ax = plt.subplots(figsize=(12, 12))
    ax.imshow(im, aspect='equal')
    for i in inds:
        bbox = dets[i, :4]
        score = dets[i, -1]

        ax.add_patch(
            plt.Rectangle((bbox[0], bbox[1]),
                          bbox[2] - bbox[0],
                          bbox[3] - bbox[1], fill=False,
                          edgecolor='red', linewidth=3.5)
            )
        ax.text(bbox[0], bbox[1] - 2,
                '{:s} {:.3f}'.format(class_name, score),
                bbox=dict(facecolor='blue', alpha=0.5),
                fontsize=14, color='white')

    ax.set_title(('{} detections with '
                  'p({} | box) >= {:.1f}').format(class_name, class_name,
                                                  thresh),
                  fontsize=14)
    print("类别" + class_name) #控制台输出了识别出的类别
    plt.axis('off')
    plt.tight_layout()
    plt.draw()

def demo(sess, net, image_name):
    """Detect object classes in an image using pre-computed object proposals."""

    # Load the demo image
    im_file = os.path.join(cfg.DATA_DIR, 'demo', image_name)
    im = cv2.imread(im_file)

    # Detect all object classes and regress object bounds
    timer = Timer()
    timer.tic()
    scores, boxes = im_detect(sess, net, im)
    timer.toc()
    print('Detection took {:.3f}s for {:d} object proposals'.format(timer.total_time, boxes.shape[0]))

    # Visualize detections for each class
    CONF_THRESH = 0.8
    NMS_THRESH = 0.3
    for cls_ind, cls in enumerate(CLASSES[1:]):
        cls_ind += 1 # because we skipped background
        cls_boxes = boxes[:, 4*cls_ind:4*(cls_ind + 1)]
        cls_scores = scores[:, cls_ind]
        dets = np.hstack((cls_boxes,
                          cls_scores[:, np.newaxis])).astype(np.float32)
        keep = nms(dets, NMS_THRESH)
        dets = dets[keep, :]
        vis_detections(im, cls, dets, thresh=CONF_THRESH)

def parse_args():
    """Parse input arguments."""
    parser = argparse.ArgumentParser(description='Tensorflow Faster R-CNN demo')
    parser.add_argument('--net', dest='demo_net', help='Network to use [vgg16 res50 res101 res152]',
                        choices=NETS.keys(), default='vgg16')  #需要更改的地方default
    parser.add_argument('--dataset', dest='dataset', help='Trained dataset [pascal_voc pascal_voc_0712]',
                        choices=DATASETS.keys(), default='pascal_voc')
    args = parser.parse_args()

    return args

if __name__ == '__main__':
    cfg.TEST.HAS_RPN = True  # Use RPN for proposals
    args = parse_args()

    # model path
    demonet = args.demo_net
    dataset = args.dataset
    tfmodel = os.path.join('output', demonet, DATASETS[dataset][0], 'default',
                              NETS[demonet][0])


    if not os.path.isfile(tfmodel + '.meta'):
        raise IOError(('{:s} not found.\nDid you download the proper networks from '
                       'our server and place them properly?').format(tfmodel + '.meta'))

    # set config
    tfconfig = tf.ConfigProto(allow_soft_placement=True)
    tfconfig.gpu_options.allow_growth=True

    # init session
    sess = tf.Session(config=tfconfig)
    # load network
    if demonet == 'vgg16':
        net = vgg16()
    elif demonet == 'res101':
        net = resnetv1(num_layers=101)
    elif demonet == 'res50':
        net = resnetv1(num_layers=50)
    elif demonet == 'res152':
        net = resnetv1(num_layers=152)
    else:
        raise NotImplementedError
    net.create_architecture("TEST", 5,
                          tag='default', anchor_scales=[8, 16, 32])
    saver = tf.train.Saver()
    saver.restore(sess, tfmodel)

    print('Loaded network {:s}'.format(tfmodel))

    root = "/content/drive/My Drive/tf-faster-rcnn/data/demo/"
    #从路径中读取图片
    for dirpath,dirnames,im_names in os.walk(root):
        for im_name in im_names:
            print ('~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~')
            print ('Demo for data/demo/{}'.format(im_name))
            demo(sess, net, im_name)
            plt.savefig("/content/drive/My Drive/tf-faster-rcnn/testfigs/" + im_name)
            #保存路径