Batch operation on tensors in TensorFlow

Question

I have a batches of images represented as TensorFlow tensor (say Tensor 1) of shape (2,1024,1024,1) of the form (B,H,W,C) where B is the batch size 2, H and W are image dimensions 1024 and C is the number of channels. Each element of this tensor (i.e. each pixel) stores a tuple (a,b) where both a and b are in the range 0 and 255.

I have another tensor (say Tensor 2) of shape (256,256) for which each element stores a single value between 0 and 255.

Given this setup, I have the following question.

I wish to replace each element value in Tensor 1 with the corresponding element value in Tensor 2. For example, let's assume that the element given by index (1,200,500,1) in tensor 1 contains the value (100,20). I want to look up the value stored in Tensor 2 at pixel location (100,200) and modify the entry at (1,200,500,1) with this value.

How can I do this in the most efficient way possible for the entire batch?

Please let me know if something is unclear. I am a beginner to TensorFlow, hence would appreciate any help.

Marco Cerliani · Accepted Answer · 2020-05-16 09:41:32Z

0

to replace an element value in Tensor 1 with a corresponding element value in Tensor 2 try this way

tensor1 = tf.Variable(tf.zeros((2,1024,1024,1)), trainable=False)
tensor2 = tf.constant(np.random.randint(0,255, (255,255,1)), dtype='float32')

tensor12 = tensor1[1,200,500].assign(tensor2[100,200])

in this example, you substituted the element in position (1,200,500,1) of Tensor 1 with the element in position (100,200) of Tensor 2

batch_dim = 2
tensor1 = tf.Variable(tf.zeros((batch_dim,1024,1024,1)), trainable=False)
tensor2 = tf.constant(np.random.randint(0,255, (1,255,255,1)), dtype='float32')

tensor12 = tensor1[:,:tensor2.shape[1],:tensor2.shape[2]].assign(tf.repeat(tensor2, batch_dim, axis=0))

with these lines, you assign all the value of tensor2 to the first (255,255) position in tensor1 for ALL the samples of the batch

edited May 16, 2020 at 9:41

answered May 16, 2020 at 8:43

Marco Cerliani

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