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 

Answer 2

Simple fix to this issue is to use an image format that supports transparency, such as png.

So:

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

Problem solved :)