enomoto celtislab

You are using a tag cloud of the standard, and you do not want to display tags that belong to the category not related to the article. 
Try this widget. 
Based on the category of the display article, this widget gets the tag from the article categories of related range. 
For the article there is no category of post page, etc., or by setting <code>all category</code>, <code>internal link article</code>, it displays the tag by examining the related category. 
If you check the ‘internal link article’, get a category from the internal links to articles.
Select Category related range
<ul>
<li>All Category (unrelated article)</li>
<li>Current article Category</li>
<li>Include child category tree</li>
<li>Include parent category tree</li>
<li>Include internal linked article Category</li>
<li>Exclude Category</li>
</ul>
Other parameters : Display format, Sort by, Order, Font size, Number of tags to display, …
<a href="http://celtislab.net/wp_plugin_DCTagCloud/" title="Documentation in Japanese" rel="nofollow ugc">日本語の説明</a>

DynamicCategoryTagCloud

Displays the tag cloud dynamically from related articles belonging to the category of the display article

WPKube

The plugin renders a tag cloud using a professionally designed tag image as a background.
The plugin’s tag cloud is completely responsive and is correctly rendered in all browsers.
The primary application of this feature is through the “Cool Tag Cloud” widget, but you can also use the shortcode [cool_tag_cloud] to display the tag cloud anywhere where shortcodes are supported.
Here is the list of parameters that can be used with the shortcode, each with its own set of potential values (which are separated by the | symbol):
<ul>
<li><code>style="default|silver|green|red|blue|brown|purple|cyan|lime|black"</code></li>
<li><code>font_family="Arial, Helvetica, sans-serif"</code></li>
<li><code>smallest="10"</code></li>
<li><code>largest="10"</code></li>
<li><code>align="left|right"</code></li>
<li><code>font_weight="normal|bold"</code></li>
<li><code>text_transform="none|uppercase|lowercase|capitalize"</code></li>
<li><code>number="20"</code></li>
<li><code>order_by="name|count"</code></li>
<li><code>order="ASC|DESC|RAND"</code></li>
<li><code>taxonomy="post_tag"</code></li>
<li><code>nofollow="yes|no"</code></li>
<li><code>animation="yes|no"</code></li>
<li><code>on_single_display="global|local"</code></li>
<li><code>on_archive_display="all|children|siblings|descendants"</code></li>
<li><code>exclude="1,2,3"</code></li>
<li><code>include="1,2,3"</code></li>
</ul>
If you liked my plugin, please rate it.
Special thanks to <a href="http://www.premiumpixels.com/freebies/tagtastic-tag-cloud-psd/" rel="nofollow ugc">Orman Clark</a> for the tag image and to <a href="http://dimox.name/beautiful-tags-markup/" rel="nofollow ugc">Dimox</a> for the CSS code.
This plugin is maintained by <a href="https://www.wpkube.com" rel="nofollow ugc">WPKube</a>, a WordPress resource site where you can find helpful guides like how to <a href="https://www.wpkube.com/list-building-wordpress-plugins/" rel="nofollow ugc">choose the right list building plugin</a>, <a href="https://www.wpkube.com/install-wordpress" rel="nofollow ugc">how to install WordPress</a>, <a href="https://www.wpkube.com/best-wordpress-hosting/" rel="nofollow ugc">choose the best WordPress hosting</a>, and more. 
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Cool Tag Cloud

This came as a blessing when I had written some custom code to show a custom Taxonomy cloud on sidebar. The options to customize are so cool, and I love the option to either show the taxonomy related to a post on a Single post page or all tags, that makes it so versatile. Thanks so much to the author.

DynamicCategoryTagCloud vs Cool Tag Cloud