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Detecting changes in images

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dgtlmoon edited this page Sep 26, 2023 · 9 revisions

Sometimes a watch has a filter that only contains an image.

At the moment, changedetection.io only supports detecting changes in the Text of the webpage, however, you can also use the source: keyword in the URL to tell changedetection to return the HTML source.

So this means that you could use changedetection to detect when the HTML now references a different image source.

For example - source at https://the-site-you-are-watching.com is

<HTML>
<BODY>
   <div id="wrapper">
      <img src="november-calendar.jpg">
   </div>
   <div id="other stuff">
     our new calendar!
    </div>
</BODY>
</HTML>

And then in the Visual Selector you chose the "wrapper" element

How to detect when the image changes?

Use the source: luke..

By adding "source:" to the start of your URL - source:https://the-site-you-are-watching.com and set a CSS/xPath filter (created in the Visual Selector tool), you will get a notification when the website changes "november-calendar.jpg" to "december-calendar.jpg"

Since 0.45.3 we've tried to add a message to help identify when this was happening

In addition to the message Got HTML content but no text found (With 200 reply code), (because there is only an image), if you specified a filter/selector , it will try to help you by saying "Got HTML content but no text found (With 200 reply code), it's possible that the filters you have give an empty result or contain only an image."

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