page_title: JPEG 2000
section_title: Compression ratio
hierarchical_section_title: JPEG 2000 / Technical discussion / Compression ratio
caption_attribution_description: The picture shows the difference pixel-by-pixel between an image and its JPEG2000 compressed version: white=no-difference; black=big-difference The original image is Image:Lichtenstein img processing test.png, that I have renamed castle.png on my hard-disk to make it simpler. The I have converted it so JPEG2000 using the "convert" utility by ImageMagik, with the following command: convert -quality 50 castle.png castle.jp2 Then I had to reconvert the JPEG2000 version to PNG to be able to read it: convert castle.jp2 castle_2000.png The I have used the following Matlab code: %read original image original=imread('castle.png'); %read compressed image compressed=imread('castle_2000.png'); original=im2double(original); compressed=im2double(compressed); error=abs(original-compressed); %amplify the error for each color layer error(:,:,1)=imadjust(error(:,:,1)); error(:,:,2)=imadjust(error(:,:,2)); error(:,:,3)=imadjust(error(:,:,3)); %invert the picture error=1-error; %write it to a file imwrite(error,'castle_error_2000.png');
context_page_description: JPEG 2000 is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi, with the intention of superseding their original discrete cosine transform based JPEG standard with a newly designed, wavelet-based method. The standardized filename extension is .jp2 for ISO/IEC 15444-1 conforming files and .jpx for the extended part-2 specifications, published as ISO/IEC 15444-2. The registered MIME types are defined in RFC 3745. For ISO/IEC 15444-1 it is image/jp2.
  JPEG 2000 code streams are regions of interest that offer several mechanisms to support spatial random access or region of interest access at varying degrees of granularity. It is possible to store different parts of the same picture using different quality.
  JPEG 2000 is a discrete wavelet transform based compression standard that could be adapted for motion imaging video compression with the Motion JPEG 2000 extension. JPEG 2000 technology was selected as the video coding standard for digital cinema in 2004.
context_section_description: Compared to the previous JPEG standard, JPEG 2000 delivers a typical compression gain in the range of 20%, depending on the image characteristics. Higher-resolution images tend to benefit more, where JPEG-2000's spatial-redundancy prediction can contribute more to the compression process. In very low-bitrate applications, studies have shown JPEG 2000 to be outperformed by the intra-frame coding mode of H.264. Good applications for JPEG 2000 are large images, images with low-contrast edges – e.g., medical images.
caption: This image shows the (accentuated) difference between an image saved as JPEG 2000 (quality 50%) and the original.
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