: Check if an image is already optimized for the web I have found this tool that optimizes images for the web. What is surprising for me (of course, there will be other tools like this :))

@Bryan171

I would just crush all of your images using a script like the one below which I use. Be sure to back up the images directory first. If any resultant images are smaller than the ones you were serving, then they weren't optimised!

#!/bin/sh

# script for optimizing images in a directory (recursive)
# pngcrush & jpegtran settings from:
# developer.yahoo.com/performance/rules.html#opt_images
# pngcrush
for png in `find -iname "*.png"`; do
echo "crushing $png ..."
pngcrush -rem alla -reduce -brute "$png" temp.png

# preserve original on error
if [ $? = 0 ]; then
mv -f temp.png "$png"
else
rm temp.png
fi
done

# jpegtran
for jpg in `find -iname "*.jpg"`; do
echo "crushing $jpg ..."
jpegtran -copy none -optimize "$jpg" > temp.jpg

# preserve original on error
if [ $? = 0 ]; then
mv -f temp.jpg "$jpg"
else
rm temp.jpg
fi
done


pngcrush comes from here: pmt.sourceforge.net/pngcrush/ jpegtran comes from here: jpegclub.org/jpegtran/

Three notes:


pngout has better compression on most files: advsys.net/ken/utils.htm [source]
For JPEGs, spit them out in various quality settings and see what the lowest acceptable quality value is (it will vary by image and destination screen size)
cwebp can probably do better on both jpegs and PNGs, but can only be used in Chrome and Opera (soon Firefox): developers.google.com/speed/webp/

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@Ann8826881

Based on your reference to the ImageMagick convert method and quality parameter, it appears you're working with JPEG images. If that's the case, the EXIF information for JPEG images does not have a standard compression level tag.

However, ImageMagick appears to be able to obtain this information from the image's quantization tables using the identify command. So try this:

identify -verbose yourimage.jpg


And then you should be able to parse out the quality level from the standard output. For example:

...
Compression: JPEG
Quality: 80
...

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