Adding a ‘style=’ bit to image_send_to_editor output

Question

I can’t find the proper hook, but there is alternative solution: to add style="float:right" to all images in content, which have class="alignright":

add_filter('the_content', 'my_add_image_float_right');

function my_add_image_float_right($content) {
    $pattern = '@(<img.+)(alignright)(.*)(/>)@Ui';
    $replacement="$1$2$3 style="float:right" />";
    $content = preg_replace($pattern, $replacement, $content);
    return $content;
}