Gagan Deep Singh

Sometimes you may want the images on your blog/site to be pixel perfect, while sometimes you may want them to be compressed to save space on the server.
This plugin allows you to select the quality of the thumbnail images generated by WordPress, as easy as that. Just go to Media Settings page and modify the Image Quality setting.
Plugin only works for new uploads, but in case you want to modify the thumbnails generated earlier, you can either use
<a href="https://wordpress.org/plugins/regenerate-thumbnails/" rel="ugc">Regenerate Thumbnails</a>
or if you are familiar with WP-CLI, then you can use this command to regenerate
<pre><code>wp media regenerate
</code></pre>
P.S. It does not change the quality of the original image that you upload, 
but only changes the quality of the thumbnails WordPress generates from that image.

Image Quality

Lets you adjust the quality of image thumbnails that WordPress generates.

crissyfieldgmbh

Convert HEIC images to JPEG format when upload to the Media Library.
HEIC is the file format name Apple has chosen for the “High Efficiency Image Format” (HEIF) standard. HEIF offers better compression than JPEG, so it takes up less storage space, while maintaining the same visual quality. The format has been used by default since iOS 11, i.e. for images sent through the Messages app or when exporting.
This plugin adds HEIC/HEIF support to WordPress by transparently converting the uploaded image to JPEG.
Note: ImageMagick 7.0.8-46 or above is required to be installed on the server.
Check <a href="/plugins/heic-support/" rel="nofollow ugc">HEIC Support</a> for an alternative solution.
<a href="https://www.flaticon.com/free-icons/iphone" rel="nofollow ugc">Iphone icon created by Smashicons</a> and <a href="https://www.flaticon.com/free-icons/photo" rel="nofollow ugc">Photos icon created by Freepik</a>.

HEIC to JPEG

Convert HEIC images to JPEG format when upload to the Media Library.

Image Quality vs HEIC to JPEG