Do JPEG Encoders Differ Significantly in Quality?

摘要

The claim is often made that JPEG encoders vary a great deal in their abilities to produce small, acceptable quality JPEG files. It has often been asserted that PhotoShop produces poor quality, "bloated" JPEGs when compared with PaintShop Pro, ImageOpti-mizer, or even PhotoShop's poor web-cousin ImageReady. For web use, where excessive download times may mean the difference between someone spending serious time browsing a site or hitting their back button in exasperation, this is an important issue. And having spent many hours building up a website that has been perhaps generously referred to as a "graphics-pig", I myself had an interest in finding out if these aims were true. So I did some research, wrote an analysis code and performed a number of experiments from which emerged some useful results.