Description:
------------
I've noticed that imagescale() permanently changes the interpolation
method, and does not use the interpolation method specified with
imagesetinterpolation(). The latter might be a documentation
issue; the imagesetinterpolation() manual page states:

| Changing the interpolation method affects the following
| functions when rendering:
| imagescale()

The former is a real bug, in my opinion, which appears to have
been introduced by fixing bug #66893.


Test script:
---------------
<?php

$src = imagecreatetruecolor(100, 100);
imagefilledrectangle($src, 0,0, 99,99, 0xFFFFFF);
imageellipse($src, 49,49, 40,40, 0x000000);

imagesetinterpolation($src, IMG_NEAREST_NEIGHBOUR);

$dst = array();
$dst[] = imagerotate($src, 60, 0xFFFFFF);
$dst[] = imagescale($src, 200, 200, IMG_NEAREST_NEIGHBOUR);
$dst[] = imagescale($src, 200, 200);
$dst[] = imagerotate($src, 60, 0xFFFFFF);

foreach ($dst as $i => $im) {
    imagepng($im, __DIR__ . DIRECTORY_SEPARATOR . "image-$i.png");
}


Expected result:
----------------
image-0.png and image-3.png as well as image-1.png and image-2.png
should be identical, respectively.


Actual result:
--------------
All images are different.