ImageMagick PDF to JPGs sometimes results in black background

Question

I have the following:

ghostscript-fonts-5.50-24
ImageMagick-6.7.2-1
ghostscript-9.02-1

Which I use to create a series of JPGs for each page using:

convert -density 175 -colorspace sRGB test.pdf -resize 50% -quality 95 test.jpg

When I run this on my windows machine all appears to work ok, but on our linux server we get the black background problem.

The resulting JPGs have a black background rendering the image un-readable, what am I missing or is there something I should be doing to correct this?

I've been all over google for days but each suggestion doesnt seem to work for me.

Any help is much appreciated, thanks in advance :)

EDIT

Just noticed this output when converting one of the PDFs that produces the black background:

**** Warning: Fonts with Subtype = /TrueType should be embedded.
             The following fonts were not embedded:
                    Arial
                    Arial,Bold
                    Arial,BoldItalic
**** This file had errors that were repaired or ignored.
**** The file was produced by:
**** >>>> Microsoft« Word 2010 <<<<
**** Please notify the author of the software that produced this
**** file that it does not conform to Adobe's published PDF
**** specification.

This seems related but as we don't have control over how the PDFs are produced we need some way of fixing this server side.

Thanks again

Answer 1

Ran into this one today, found this:

https://www.imagemagick.org/discourse-server/viewtopic.php?t=20234

Based on that, these should all work:

• -flatten
• -alpha flatten
• -alpha remove

I'm currently using the below for my specific case which works great:

convert -thumbnail "1280x800>" -density 300 -background white -alpha remove in.pdf out.jpg