I agree with this based on my fuzzy impressions of my own past experience, but I never did any careful explicit tests. It’s too bad the original source image used for the comparison in the document you linked is really crappy quality with terrible artifacts though, and the resizing routine is the fairly unimpressive bicubic scaling (or in the first example nearest neighbor). Makes the comparison pretty useless IMO.
I’d love to see a similar comparison starting with a much better source image, but I don’t have time to do the tests myself right now.
I’d also love to see a comparison of (a) a high-quality image downscaled using a very high quality resizing algorithm and then JPEG compressed versus (b) JPEG compressed first to match the size of image a and then resized in-browser by various browsers’ resizing routines. There was a pretty big difference between the way browsers resize images the last time I checked a few years ago.
I’d love to see a similar comparison starting with a much better source image, but I don’t have time to do the tests myself right now.
I’d also love to see a comparison of (a) a high-quality image downscaled using a very high quality resizing algorithm and then JPEG compressed versus (b) JPEG compressed first to match the size of image a and then resized in-browser by various browsers’ resizing routines. There was a pretty big difference between the way browsers resize images the last time I checked a few years ago.