Converting all .pdf files in folder tree to .png - bash

Question

I'm on Ubuntu, and I have a tree of folders containing .pdf files. I need to convert each one to a .png format. The bash script I am currently using is:
for f in $(find ./polkadots -name 'image.pdf'); do
convert -transparent white -fuzz 10% $f image.png;
done
I have tested the for loop by itself, and it works (it produces a list of all the .pdf files under the ./polkadots folder that I need to convert):
for f in $(find ./polkadots -name 'image.pdf'); do
echo "$f";
done
I have tested the imagemagic convert command by itself, and it works (it converts a single file in my current directory from .pdf to .png):
convert -transparent white -fuzz 10% image.pdf image.png
However, when I combine them... the console sits and thinks for a while, and then concludes.. but no files have been created or changed, and no error messages are produced. What am I doing wrong?
EDIT: The new .png files are being created, but they are being created in my current directory, instead of in the sub-directory where the .pdf was found. How do I fix this?

Answer 1

Try using find alone. No need to use a loop.
I haven't tested this command but it should work.
find ./polkadots -name 'image.pdf' -exec convert -transparent white -fuzz 10% {} image.png \; -print
The -print at the end is optional. I prefer to see which files have been modified.

Answer 2

Maybe you can find output option in convert command directly, which can export the png file to your expect folder. Anyway follow your idea, here is the updated code:
find ./polkadots -type f -name "image.pdf" |while read line
do
dir=${line%/*}
convert -transparent white -fuzz 10% $line image.png
mv image.png ${dir}/image.png
done
If you need convert all pdf files under polkadots folder, try this:
find ./polkadots -type f -name "*.pdf" |while read line
do
dir=${line%/*}
file=${line##*/}
file=${file%.*}
convert -transparent white -fuzz 10% $line ${file}.png
echo mv ${file}.png ${dir}/${file}.png
done

Answer 3

If you are using bash 4+, you should use globstar instead of find
#!/bin/bash
shopt -s globstar
for f in ./polkadots/**/image.pdf; do
convert -transparent white -fuzz 10% "$f" "${f%/*}/image.png"
done
If you're using an older bash, your original answer is close to fine, but has a few bugs/potential bugs,
If you directories have spaces in them, your original script will case errors, so use the | while read -r -d '' f syntax.
Don't put a ; at the end of command lines
Quote all variables to prevent expansion problems
As you pointed out, main issue in your case was not specifying destination dir, so you can use ${f%/*} parameter expansion to get the dir (this will delete everything including and after the last / in $f, then put the / back and append the filename like below.
Edited
#!/bin/bash
find ./polkadots -name "image.pdf" -print0 | while read -r -d '' f; do
convert -transparent white -fuzz 10% "$f" "${f%/*}/image.png"
done