I am manipulating images using Image Magick. Here is the command that I use:
convert source.png -resize 1200 -quality 75 result.jpg
It works as expected. I am no wondering whether there is a way to report a conversion result showing how much compression has been done (in percentage or kilobyte or just by showing the sizes of original and converted images)?
I have tried -monitor switch, but it only shows a progress kind of report during conversion.
(I am using Linux)
The quality setting you use tells ImageMagick how much to compress the image. Alternately, you can compute the ratio of the output file size by the input size. Or the ratio of the output file size with -quality 75 to that when using -quality 100, even though -quality 100 still compresses some.
You can get the size of the image by
convert image -precision 16 -format "%b\n" info:
Setting a large precision will forces the result to be in Bytes, but you will have to remove the B character from the end. So you can do the following to get the percent of output/input file sizes:
outsize=$(convert output -precision 16 -format "%b\n" info: | sed 's/B//g')
insize=$(convert input -precision 16 -format "%b\n" info: | sed 's/B//g')
percent_size=$(convert xc: -format "%[fx:100*$outsize/$insize]\n" info:)