Hello! I do not know very well the php ...
What code should be added to image.php to display the resolution and size (height and width, size in kilobytes or megabytes) of the large (original, full) image?
For example, it works in the admin panel - displays: Dimensions, Size.

I suggest you explore the admin panel code and see how it does this. You can then copy what it does. Generally programming is mostly about finding code somewhere that does mostly what you want and adapting it to your needs.

So, for instance, if you do a search of the source for "Dimensions:" {the source code is in English} you will find the line in admin-edit.php that displays the height and width. Below that line is the code for the size.

Here is the code I have for showing image dimensions.

'
<?php echo gettext("Original Size:"); ?>
<a>" title="<?php echo getBareImageTitle();?>">
<?php echo getFullWidth() . "x" . getFullHeight(); ?>px
'</a>

Good! I hope that happens.)))

Thank you very much, Sean!!!