Image guidelines

Prior to committing images please read this guide:

JPEG

• Only use JPEGs for photographs, do not use JPEGs for icons and logos
• Crop images so that any unnecessary content is removed
• Use ImageMagick with the following commands for all JPEG images prior to committing them to the repository:

convert -strip -sampling-factor 4:2:0 -interlace line -quality 70 input.jpg output.jpg

You can use the following if you want to convert multiple images within the current directory

while IFS= read -r file; do                                                                                                       
  convert -strip -sampling-factor 4:2:0 -interlace line -quality 70 $file $file
done < <(find . -type f -name "*.jpg")

You may alter the quality if the output is unacceptable for a given image (however you should avoid values > 90).

PNG

• Do not use PNGs for photographs, only use PNGs for icons and logos
• Crop PNGs so that only the required content remains (e.g. remove transparent borders if any).
• Use Pngcrush with the following commands for all PNGs prior to committing them to the repository:

pngcrush -rem gAMA -rem cHRM -rem iCCP -rem sRGB -rem alla -rem text -reduce input.png ./output/output.png

You can use the following if you want to convert multiple PNGs within the current directory

while IFS= read -r file; do                         
  pngcrush -rem gAMA -rem cHRM -rem iCCP -rem sRGB -rem alla -rem text -reduce $file ./output/$file
done < <(find . -type f -name "*.png")

SVG

Use https://github.com/svg/svgo to optimize svg's w/ multipass option, e.g.:

svgo --multipass app/assets/images/logo.svg

Note: In case dimensions or width/height parameters are required the optimization might remove them, so be sure to add them back if relevant.