WP_Image_Editor Flip Method $horz and $vert arguments are backwards

[alconebay]

The WP_Image_Editor class shows:

/**
 * @param boolean $horz Horizontal Flip
 * @param boolean $vert Vertical Flip
 */
abstract public function flip( $horz, $vert );

But changing the first argument to true flips the image vertically and the second argument, when true, flips the image horizontally.
Both imagemagick and GD are affected.

A fix for class-wp-image-editor-imagick.php would be reversing lines 366 and 369 (flopImage for $horz and flipImage for $vert)

A fix for class-wp-image-editor-gd.php would be reversing $horz and $vert on lines 292-295 like this (fixed):

$sx = $horz ? ($w - 1) : 0;
$sy = $vert ? ($h - 1) : 0;
$sw = $horz ? -$w : $w;
$sh = $vert ? -$h : $h;

I've verified these fixes.

[dh-shredder]

Describe Flip Better

[dh-shredder]

I think the issue here is an understanding on what vertical and horizontal means.

You're right, the current comments make it confusing!

Horizontal means a flip along the horizontal axis.
Vertical means a flip along the vertical axis.

I've attached 23775.diff​​, which revises the phpdoc to better explain what flips the booleans control.

[alconebay]

Nevermind. You are correct! Thanks

[ryan]

In 23750:

Clarify phpdoc for the vertical and horizontal arguments to the flip() method in WP_Image_Editor*.

Props dh-shredder
fixes #23775