I've displayed a current publish content that is a picture, i have to change image size that specific image.

As @fabrik highlights @Marc B's solution works, climax not elegant.

Though, it really works. Whether it's the very first image within the publish, then remove the very first tag in the wordpress_content then apply the filter to intentionally set the width and/or height.

When the image attached may be the featured image or perhaps a custom attribute, simply do exactly the same factor except filter that data item rather than the publish content.