JPEG vs. JPEG 2000

Introduction

The JPEG2000 file format was put forward as an improvement on the classic JPEG format. JPEG2000 was created by JPEG committee (Joint Photographic Experts Group) back in 2000 hence the name for the format. It was supposed to improve on the original JPEG format (which was created back in 1992). The standardized file extension for JPEG2000 is .jp2 and .jpx.

JPEG2000 offers:

• Better efficiency in compression (including 48 bit color depth support)
• Possibility of lossless compression>
• Decoding with different output resolutions>
• A process to calculate the integrated bit rate (possibility of reaching an aimed bit rate)
• Dividing the image into smaller parts to be coded independently from the others
• Improvement in noise resilience
• Access to the compressed bit rate at any point in order to access the image directly
• Better performances in coding/decoding through many different cycles
• More flexible file format

The current reality

Similar to JPEG there's no requirement to implement to complete standard which can result in incompatibilities between different applications (it was the same in the early days of JPEG). While the complexity of the implementation didn't really help to boost the acceptance in the field JPEG2000 is now slowly entering the mainstream. The very latest imaging applications often offer a JPEG2000 file format though it still tends to be limited to 24 bit color depth.

The following images are ENLARGED BY 200% for a better illustration of the differences:

ORIGINAL IMAGE

JPEG2000 1:20

JPEG 1:20

A compression rate of 1:20 is quite extreme and naturally even JPEG2000 can't recreate the fine structures of the original image. Nonetheless it does a much better job than JPEG here. You may notice that the (in-) famous blocks (the 8x8 pixel blocks from the cosine transformation) are no longer present in the JPEG2000 image. The halo artifacts around contrast transitions (e.g. roof to sky) are also much less pronounced and there're no extreme color defects. Overall the JPEG2000 result looks soft, like sprinkled with water, but it isn't completely unusable like the JPEG result. 

Other examples:

Original

JPEG at 10% of original file size.

 Some of the fine-grained noise is smoothed out.  Some subtle 'ghost' contrast artifacts are found around areas of high contrast, such as the shoreline border.

JPEG2000 at 10% of original filesize

'Ghost' contrast artifacts are also present here, in different areas.  Fine-grained noise and small feature contrast, however, is heavily affected, causing a blurring effect.  This is easy to see in the green fields of the lower-right quadrant, where the features have blurred into mush.