No. There are lots of ways of producing JPEGs with similar visual characteristics but fairly different byte sizes. For example MozJPEG is known to quite effic

No. There are lots of ways of producing JPEGs with similar visual characteristics but fairly different byte sizes. For example MozJPEG is known to quite efficient, and a tool such as jpegtran can reduce size without changing even a single pixel. https://www.earth.org.uk/script/lossless_JPEG_compress.sh https://www.earth.org.uk/script/lossless_JPEG_compress.sh