如何在shell中为graphicsmagick编写循环？

Question

I managed (with the help of SO) to make perfect png-snippets from a pdf file with graphicsmagick . My pdf contains text and formula each "snippet" on a single page. My command trims the content of a page to the very content and finally scales this up to 2000 pixel width.

Untill now, I need to repeat that command for each single page in every pdf. I am wondering how to automate this. I think I could try a loop for the repetition of the command for every page i untill the last page.

Assume file1.pdf is in my current working directory.

gm convert -density 300x300 file1.pdf[0] -trim -resize 2000x file1_page1.png
gm convert -density 300x300 file1.pdf[1] -trim -resize 2000x file1_page2.png
gm convert -density 300x300 file1.pdf[2] -trim -resize 2000x file1_page3.png
...

How can I set a counter and run a loop for every page in my document?

Answer 1

You are in luck. GraphicsMagick knows how to do that for you:

gm convert -density 300x300 input.pdf -trim -resize 2000x +adjoin output-%d.png

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If you are ok using ImageMagick instead, you can set the starting output file number to 1 instead of 0 and don't need the -adjoin :

convert -density 300x300 input.pdf -scene 1 -trim -resize 2000x output-%d.png

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Or, if you want them all done in parallel, use GNU Parallel :

parallel gm convert -density 300x300 {} -trim -resize 2000x output-{#}.png  ::: $(identify input.pdf | awk '{print $1}')

Answer 2

for file in *.pdf
do
    pages=$(identify "$file" | wc -l)
    for (( i=0; i<$pages; i++ ))
    do
        name=$(sed "s/\.pdf$/$i.png/g" <<< "$file");
        gm convert -density 300x300 "$file[$i]" -trim -resize 2000x "$name"
    done
done

Try this one. It will convert every page in every *.pdf file to .png.