Question

我正在试图弄清楚如何在Tensorflow中动态确定图像。下面是我想要完成的一个例子，但是我似乎无法使它工作。基本上，我想在图形中为图像提供图像和裁剪值，然后继续对这些裁剪的部分进行其他计算。我目前的尝试：

import tensorflow as tf
from matplotlib import pyplot as plt
import numpy as np

sess = tf.InteractiveSession()

img1 = np.random.random([400, 600, 3])
img2 = np.random.random([400, 600, 3])
img3 = np.random.random([400, 600, 3])

images = [img1, img2, img3]

img1_crop = [100, 100, 100, 100]
img2_crop = [200, 150, 100, 100]
img3_crop = [150, 200, 100, 100]

crop_values = [img1_crop, img2_crop, img3_crop]

def crop_image(img, crop):
    tf.image.crop_to_bounding_box(img,
                                  crop[0],
                                  crop[1],
                                  crop[2],
                                  crop[3])


image_placeholder = tf.placeholder("float", [None, 400, 600, 3])
crop_placeholder = tf.placeholder(dtype=tf.int32)
sess.run(tf.global_variables_initializer())

cropped_image = tf.map_fn(lambda img, crop: crop_image(img, crop), elems=[image_placeholder, crop_placeholder])
result = sess.run(cropped_image, feed_dict={image_placeholder: images, crop_placeholder:crop_values})

plt.imshow(result)
plt.show()

/Users/p111/anaconda/bin/python /Users/p111/PycharmProjects/analysis_code/testing.py
Traceback (most recent call last):
  File "/Users/p111/PycharmProjects/analysis_code/testing.py", line 31, in 
    cropped_image = tf.map_fn(lambda img, crop: crop_image(img, crop), elems=[image_placeholder, crop_placeholder])
  File "/Users/p111/anaconda/lib/python3.5/site-packages/tensorflow/python/ops/functional_ops.py", line 390, in map_fn
    swap_memory=swap_memory)
  File "/Users/p111/anaconda/lib/python3.5/site-packages/tensorflow/python/ops/control_flow_ops.py", line 2636, in while_loop
    result = context.BuildLoop(cond, body, loop_vars, shape_invariants)
  File "/Users/p111/anaconda/lib/python3.5/site-packages/tensorflow/python/ops/control_flow_ops.py", line 2469, in BuildLoop
    pred, body, original_loop_vars, loop_vars, shape_invariants)
  File "/Users/p111/anaconda/lib/python3.5/site-packages/tensorflow/python/ops/control_flow_ops.py", line 2419, in _BuildLoop
    body_result = body(*packed_vars_for_body)
  File "/Users/p111/anaconda/lib/python3.5/site-packages/tensorflow/python/ops/functional_ops.py", line 380, in compute
    packed_fn_values = fn(packed_values)
TypeError: () missing 1 required positional argument: 'crop'

编辑：看来elems只接受一个张量。这意味着我需要以某种方式将我的两个张量合并为一个，然后在我的函数中解压缩以获取值。我不确定如何进行那种张量操纵。我已经找到了glimpse方法，但确实有效，但我想知道是否可以使用这种特定方法完成相同的操作。大多数情况下，我想知道你将如何组合然后分割一对张量，以便它可以用于这种方法。

Answer 1

我在here看到了这段代码。

elems = (np.array([1, 2, 3]), np.array([-1, 1, -1]))
alternate = map_fn(lambda x: x[0] * x[1], elems, dtype=tf.int64)
# alternate == [-1, 2, -3]

可以使用元组或列表将多个元素打包成一个，所以我尝试了这个。

import tensorflow as tf
from matplotlib import pyplot as plt
import numpy as np

sess = tf.InteractiveSession()

img1 = np.random.random([400, 600, 3])
img2 = np.random.random([400, 600, 3])
img3 = np.random.random([400, 600, 3])
images = np.array([img1, img2, img3])
# images = tf.convert_to_tensor(images)  # it can be uncommented.

img1_crop = [100, 100, 100, 100]
img2_crop = [200, 150, 100, 100]
img3_crop = [150, 200, 100, 100]
crop_values = np.array([img1_crop, img2_crop, img3_crop])
# crop_values = tf.convert_to_tensor(crop_values)  # it can be uncommented.

def crop_image(img, crop):
    return tf.image.crop_to_bounding_box(img,
                                         crop[0],
                                         crop[1],
                                         crop[2],
                                         crop[3])

fn = lambda x: crop_image(x[0], x[1])
elems = (images, crop_values)

cropped_image = tf.map_fn(fn, elems=elems, dtype=tf.float64)
result = sess.run(cropped_image)

print result.shape

plt.imshow(result[0])
plt.show()

它适用于我的机器，版本为0.11和python2。希望这可以帮到你。

Answer 2

一些事情：

return函数中没有crop_image语句。
map_fn接受一个论点。
我强烈建议您将图表定义和会话使用分开。

-

# Graph def
def crop_image(img, crop):
    return tf.image.crop_to_bounding_box(img,
                                  crop[0],
                                  crop[1],
                                  crop[2],
                                  crop[3])

image_placeholder = tf.placeholder(tf.float32, [None, 400, 600, 3])
crop_placeholder = tf.placeholder(dtype=tf.int32)
cropped_image = tf.map_fn(lambda inputs: crop_image(*inputs), elems=[image_placeholder, crop_placeholder], dtype=tf.float32)


# Session
sess = tf.InteractiveSession()

img1 = np.random.random([400, 600, 3])
img2 = np.random.random([400, 600, 3])
img3 = np.random.random([400, 600, 3])

images = [img1, img2, img3]

img1_crop = [100, 100, 100, 100]
img2_crop = [200, 150, 100, 100]
img3_crop = [150, 200, 100, 100]

crop_values = [img1_crop, img2_crop, img3_crop]

sess.run(tf.global_variables_initializer())

result = sess.run(cropped_image, feed_dict={image_placeholder: images, crop_placeholder:crop_values})

plt.imshow(result[0])
plt.show()

Answer 3

tf.map_fn（f，l）为列表l中的每个张量运行函数f。在您的情况下，您的函数需要2个参数，但由于您提供了一个平面列表，map_fn（）会逐个发送它们。根据文档，map_fn（）支持变量arity，所以你应该做的就是这样

tf.map_fn(lambda img, crop: crop_image(img, crop), 
          elems=([image_placeholder, crop_placeholder], ))

所以传递给map_fn的列表包含参数对。

Tensorflow中的动态图像裁剪

3 个答案: