DjVuPhoto vs JPEG: Head to Head Comparison
DjVuPhoto, DjVu's wavelet-based image compression technique is optimal for photos, paintings, and other continuous-tone images. Here is a head-to-head comparison of DjVuPhoto and JPEG for photos of various resolutions and qualities. DjVu can produce files about half the size of JPEG for the same quality, with the added advantage of progressive rendering, and low-memory usage.
The benchmark uses the image on the right to compare JPEG and DjVuPhoto (the DjVu wavelet-based compression technology also known as IW44).
The advantages of DjVuPhoto over JPEG are made clear:
- much higher quality than similarly sized JPEGs, or about half the size for a similar quality;
- superior quality at high compression ratios (with graceful degradation, no "block" artifacts, and no color quantization artifacts);
- very fast inital display with subsequent refinements (progressivity);
- fast decoding, zooming, panning;
- low memory usage through on-the-fly decompression allows the display of very high-resolution images on modest PC configurations.
How the Images were Produced
The image was scanned from a slide with a slide scanner into a 3306x2450 pixel image, and then stored in JPEG with quasi-lossless quality (3:1 compression ratio). This original image can be obtained here (8,043,046 Bytes) [note: this image is Copyright Eric Cosatto 1999, use only for research purpose].
This image was then reduced by factors of 2,4,8, and 16, and compressed to JPEG at various quality settings using the Independent JPEG Group's program "cjpeg -q [percent-quality]" on Unix.
For each JPEG image (at each resolution and quality setting) a corresponding DjVu image of identical resolution was produced so as to approach the file size of the JPEG version as closely as possible. This was done using the program "c44 -size xxxxx+yyyyy+zzzzz [ppmfile] [djvufile]" on Unix.
Help on Navigating the Comparison Page
- Pick an image resolution from the menu in the top left area.A list of links to DjVu and JPEG images at the chosen resolution with various quality settings will appear in the left frame.
- click on one of the DjVuPhoto or JPEG links on the left and the corresponding image will appear in the apropriate window. The size in bytes, the compression ratio and the number of bits per pixel are given for each image.
- set the zoom factor of the DjVu image to 100% for best comparison with JPEG.
- click on the "THUMBNAILS" icon to display snippets of the JPEG and DjVu versions of the image at all the available quality settings.
We suggest do not download the highest resolution JPEG images unless you have lots of RAM and a lot of patience (but don't hesitate to download their DjVu counterparts)
Note: this document is in DjVu. If you do not already have the DjVu Plug-in installed on your system, you will need to download the Plug-in before you can view the slides.