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<< Go back

https://hub.docker.com/r/rboonzaijer/imagemagick/tags

Docker image: imagemagick

Contents

  • imagemagick + ghostscript (with enabled policies to convert images to PDF etc)
  • usage: just mount the current directory and use the commands

Show versions

docker run --rm rboonzaijer/imagemagick sh -c 'gs --version && convert -version'

Convert to other format

# to webp
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/logo.png example-logo.webp

# to png
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/square.jpg example-square.png

# to jpg (note differences when converting transparent backgrounds!)
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/logo.png example-jpg-ugly.jpg
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/logo.png -background black -flatten -alpha off example-jpg-bg-black.jpg
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/logo.png -background white -flatten -alpha off example-jpg-bg-white.jpg
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/logo.png -background "#41bf6b" -flatten -alpha off example-jpg-bg-hex-green.jpg

# to PDF (simple method, uses the image sizes, each page has a different size)
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/logo.png examples/landscape.jpg examples/square.jpg examples/portrait.jpg example-document.pdf

Create custom PDF

Page Dimensions
A5 1748x2480
A4 2480x3508
A3 3508x4961

Step 1: Create a list of all images

docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick find ./examples/ -type f \( -name *.png -or -name *.jpg \) | sort > ./imagemagick/example-pdf-step1.txt

Step 2: Make sure each image is not larger then the given dimensions

# Note: change 2480x3508 to your dimensions
# Note: for a padding of 200, subtract it from the resolution: 2280x3308

# Example: with upscaling (the images can grow beyond their original sizes)
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert @./example-pdf-step1.txt -resize 2280x3308 example-pdf-step2-%d.png

# Or: without upscaling (the images will not be bigger then their original resolution) -> add '\>' after resize
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert @./example-pdf-step1.txt -resize 2280x3308\> example-pdf-step2-%d.png

Step 3: Scale the background of the image to match the wanted dimensions

# Note: change 2480x3508 to your dimensions
# Note: change '-background white' to your prefered color (black, '#41bf6b', ...)
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert example-pdf-step2-*.png -background 'white' -gravity center -extent 2480x3508 example-pdf-step3-%d.png

Step 4: Combine all pngs into 1 PDF

docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert example-pdf-step3-*.png example-pdf-step4.pdf

One-liner

Well almost... create the txt file with a list of images first (step 1)

# A4, no upscale
docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick sh -c 'WIDTH=2480;HEIGHT=3508;PADDING=200;BACKGROUND="white";INPUT=./example-pdf-step1.txt;OUTPUT=./example-a4-no-upscale.pdf; INNERWIDTH=$((${WIDTH}-${PADDING})) && INNERHEIGHT=$((${HEIGHT}-${PADDING})) && OUTER="${WIDTH}x${HEIGHT}" && INNER="${INNERWIDTH}x${INNERHEIGHT}" && echo -e "\nPADDING=${PADDING}\nOUTER=${OUTER}\nINNER=${INNER}\nINPUT=${INPUT}\n" && cat $INPUT && echo -e "\n[1/3] resizing to max fit" && convert @$INPUT -resize ${INNER}\> /tmp/page-%d.png && echo "[2/3] resizing background to exact resolution" && convert /tmp/page-*.png -background ${BACKGROUND} -gravity center -extent ${OUTER} /tmp/page-%d.png && echo "[3/3] generating pdf" && convert /tmp/page-*.png "${OUTPUT}"'

# A4, upscale

Adjust image quality (1-100)

docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/portrait.jpg -quality 80 example-quality-80.webp

docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/portrait.jpg -quality 80 example-quality-80.jpg

docker run --rm -u $(id -u):$(id -g) -v ./imagemagick:/app rboonzaijer/imagemagick convert examples/portrait.jpg -quality 80 example-quality-80.png

Note: at 100% quality the filesize has largely increased, depending on the usecase you might settle for a smaller resolution (the 80% quality of webp and jpg seems good enough for a website)

Quality Filesize (webp) Filesize (jpg) Filesize (png)
original (jpg) - 414 kB -
100 457 kB 416 kB 696 kB
90 53 kB 100 kB 669 kB
80 22 kB 55 kB 648 kB
70 18 kB 39 kB 648 kB