bug#38109: 27.0.50; xpm image scaling doesn't work

[Eli Zaretskii]

> Date: Thu, 07 Nov 2019 22:11:14 +0100
> From: Adam Sjøgren via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> I *think* scaling of xpm images used to work (maybe back when
> ImageMagick did the scaling?) - but it doesn't now, e.g. if you go:
> 
>   (insert-image (create-image 
> "/usr/src/emacs/etc/images/smilies/medium/wry.xpm" nil nil :scale 20.0))
> 
> a tiny 16x16 image is inserted. The expected result was a huge 320x320
> image.

You need to build either with XRender support (should be automatic if
you have it installed) or with ImageMagick.  Does config.h define
HAVE_XRENDER to 1?