ValueError: Dimensions must be equal, but are 1 and 3 for 'Conv2D' (op: 'Conv2D') with input shapes: [1,400,400,1], [1,3,3,1]

Question

i am trying to create a simple one layer convolution for a 2D input the idea is just to have an input image , kernel and an output the code is :

import tensorflow as tf
import numpy as np
from PIL import Image
import matplotlib.pyplot as plt

filename_queue = tf.train.string_input_producer(['/home/ubuntu/test.png']) 

reader = tf.WholeFileReader()
key, value = reader.read(filename_queue)

my_img = tf.image.decode_png(value) 

init_op = tf.initialize_all_variables()
sess = tf.InteractiveSession()
with sess.as_default():
    sess.run(init_op)

coord = tf.train.Coordinator()
threads = tf.train.start_queue_runners(coord=coord)

for i in range(1): 
  image = my_img.eval() 
image = tf.cast(image, tf.float64)
image = tf.expand_dims(image, 0)

K=np.array([[0,1,0],[1,1,1],[0,1,0]]).astype(float)
K = tf.expand_dims(K, 2)
K = tf.expand_dims(K, 0)


conv = tf.nn.conv2d(
        image,
        K,
        strides=[3, 3, 3, 3],
        padding="SAME")

and i am getting this error:

Traceback (most recent call last):
  File "test4.py", line 35, in <module>
    padding="SAME")
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/ops/gen_nn_ops.py", line 396, in conv2d
    data_format=data_format, name=name)
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/op_def_library.py", line 759, in apply_op
    op_def=op_def)
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/ops.py", line 2242, in create_op
    set_shapes_for_outputs(ret)
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/ops.py", line 1617, in set_shapes_for_outputs
    shapes = shape_func(op)
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/ops.py", line 1568, in call_with_requiring
    return call_cpp_shape_fn(op, require_shape_fn=True)
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/common_shapes.py", line 610, in call_cpp_shape_fn
    debug_python_shape_fn, require_shape_fn)
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/common_shapes.py", line 675, in _call_cpp_shape_fn_impl
    raise ValueError(err.message)
ValueError: Dimensions must be equal, but are 1 and 3 for 'Conv2D' (op: 'Conv2D') with input shapes: [1,400,400,1], [1,3,3,1].

my input is 400x400x1 and the kernel is 3x3

Answer 1

Based on conv2d doc:

shape of input = [batch, in_height, in_width, in_channels]
shape of filter = [filter_height, filter_width, in_channels, out_channels]

Last dimension of input and third dimension of filter represents the number of input channels. In your case they are not equal.

You can change the shape of filter to [3, 3, 1, 1].