Schema.org ImageObject url

Question

Schema.org’s ImageObject example uses itemprop="contentUrl".

I tested this simplified code in Google: https://search.google.com/structured-data/testing-tool gives me an error:

A value for the url field is required

<div itemscope itemtype="http://schema.org/Article">    
<div itemprop="image" itemscope itemtype="http://schema.org/ImageObject">
    <img itemprop="contentUrl" src="1.png" alt="alt of the image">
    <p itemprop="caption">Caption of the image</p>
</div>
<h1 itemprop="name">Title of the post</h1>
<div itemprop="articleBody" class="text">       
    <p>This is the body of the post</p>
</div>
</div>

How to solve that error in Google?

Answer 1

You can provide the url property in addition to the contentUrl property:

<img itemprop="contentUrl url" src="1.png" alt="alt of the image">

(Ideally Google would use/require contentUrl instead of url for the image for their Article rich result.)