how to convert PDF to PNG without converting white background intro transparency

Question

I am converting a PDF (which I made with R) to a PNG with a command like this:

convert -density 200 foo.pdf bar.png

This generates a PNG allright, but the white background is transparent in the resulting PNG. This is not what I want, I want the background to be white in the PNG as well. How can I achieve this?

Notes:

• I am using Xubuntu.
• What is weird, I did the same sequence on a different linux and computer: first generate picture with R in PDF format, then convert from PDF to PNG, and on that installation it does not convert the white background into transparency, just as I want it. But, I do not know where the difference is caused (R, convert or what).

Answer 1

Try to add this setting:

-flatten

Source

Answer 2

Best way is to add -alpha remove -alpha off because -flatten merges all pages if any and would be depreciated ( -layers flatten is recommended )