Answers.Body: <p>It seems that they are informally using the term &quot;sub-region&quot; to refer to the section of the image with which you multiply the kernel to produce a scalar value of the <strong>feature map</strong> (which they call <em>pixel</em>, but I would use the term <em>pixel</em> only to refer to the scalar values of the image). So, it seems that a sub-region is a synonym for <strong>receptive field</strong>. We have a question on the difference between receptive fields and feature maps <a href="https://ai.stackexchange.com/q/8701/2444">here</a>.</p>
  
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Answers.CreationDate: 2021-10-27T13:03:12.477Z
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Body: <p>Consider the following sentences from the research paper titled <a href="https://arxiv.org/pdf/1703.06339.pdf" rel="nofollow noreferrer">PatternNet: Visual Pattern Mining with Deep Neural Network</a> by <em>Hongzhi Li et al</em>.</p>
  <blockquote>
  <p>The value of each pixel in a feature map is the response of a filter
  with respect to a <strong>sub-region of an input image</strong>. A high value for a
  pixel means that the filter is activated by the content of the
  <strong>sub-region of the input image</strong>.</p>
  </blockquote>
  <p>The sentences mention the <strong>sub-regions of an image</strong>. Is there any formal definition for a sub-region of an image?</p>
  
Tags: <definitions><image-processing>
Title: What is meant by sub-region of an image?
UserDisplayName: hanugm
ThreadText: # What is meant by sub-region of an image?
  
  (Asked by: username_0 on 2021-10-27)
  
  Consider the following sentences from the research paper titled [PatternNet: Visual Pattern Mining with Deep Neural Network](https://arxiv.org/pdf/1703.06339.pdf) by *Hongzhi Li et al*.
  
  > The value of each pixel in a feature map is the response of a filter
  > with respect to a **sub-region of an input image**. A high value for a
  > pixel means that the filter is activated by the content of the
  > **sub-region of the input image**.
  
  The sentences mention the **sub-regions of an image**. Is there any formal definition for a sub-region of an image?
  
  **Tags:** definitions, image-processing
  
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  ## 1 answers
  
  ### Answer by username_1 on 2021-10-27. Score: 1
  
  It seems that they are informally using the term "sub-region" to refer to the section of the image with which you multiply the kernel to produce a scalar value of the **feature map** (which they call *pixel*, but I would use the term *pixel* only to refer to the scalar values of the image). So, it seems that a sub-region is a synonym for **receptive field**. We have a question on the difference between receptive fields and feature maps [here](https://ai.stackexchange.com/q/8701/2444).
  
  
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