Image Optimization, Part 4: Sequential JPEG - to be or not to be?

Note: below is the translation of the note “Image Optimization, Part 4: Progressive JPEG ... Hot or Not?” From the YUI blog. In it, already known from past articles, Stoyan Stefanov considers the use of sequential (progressive) JPEG from the point of view of client optimization. My comments further in italics.

In his previous article , Image Optimization, Part 3: 4 Steps to Reduce File Size, consecutive JPEG files were casually mentioned as one of the possibilities for optimizing JPEG. This article addresses this issue more deeply, including the results of an experiment conducted on 10,000 images.

Baseline and sequential JPEG

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Baseline JPEGs are “regular”: files of this type are supported by all image editing programs. Browsers download them sequentially, top to bottom, as information arrives from the network.



Download a basic jpeg file in a browser. By clicking the full version will open.

Sequential JPEGs are another variation of this format: they are loaded (as the name implies) sequentially. First you will see a poor quality picture. Then, as graphic information becomes available, the image quality will gradually improve.



Download successive jpeg. By clicking the full version will open.

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