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More info?)
Wayne Fulton posted:
"... Browsers dont know about JPG2000, and many image programs dont know about it either.
<snip>
A TIF file will be better yet (browsers dont do TIF either).
...."
That's part of the reason I personally do not use either of the "JPEG" compression
formats. However, you should take a look at PNG. It has many of the advantages of TIF ...
and most of the major browsers *do* know about it.
See
http://www.w3.org/TR/PNG/
Abstract
This document describes PNG (Portable Network Graphics), an extensible file format for the
lossless, portable, well-compressed storage of raster images. PNG provides a patent-free
replacement for GIF and can also replace many common uses of TIFF. Indexed-color,
grayscale, and truecolor images are supported, plus an optional alpha channel. Sample
depths range from 1 to 16 bits.
PNG is designed to work well in online viewing applications, such as the World Wide Web,
so it is fully streamable with a progressive display option. PNG is robust, providing both
full file integrity checking and simple detection of common transmission errors. Also, PNG
can store gamma and chromaticity data for improved color matching on heterogeneous
platforms.
This specification defines an Internet Media Type image/png.
http://www.libpng.org/pub/png/pngapbr.html
http://www.w3.org/TR/PNG-Rationale.html
http://www.w3.org/TR/PNG-GammaAppendix.html
http://www.libpng.org/pub/png/pngapbr.html
The disadvantages are shown on some of the pages referenced above, but one of the primary
ones is no support for alternate color spaces ... such as CMYK, etcetera. However for
archiving use, or for illustrations used on web pages, this is not a problem.
Disadvantages include
There is no uncompressed variant of PNG. It is possible to store uncompressed data by
using only uncompressed deflate blocks (a feature normally used to guarantee that deflate
does not make incompressible data much larger). However, PNG software must support full
deflate/inflate; any software that does not is not compliant with the PNG standard. The
two most important features of PNG---portability and compression---are absolute
requirements for online applications, and users demand them. Failure to support full
deflate/inflate compromises both of these objectives.
There is no lossy compression in PNG. Existing formats such as JFIF already handle lossy
compression well. Furthermore, available lossy compression methods (e.g., JPEG) are far
from foolproof --- a poor choice of quality level can ruin an image. To avoid user
confusion and unintentional loss of information, we feel it is best to keep lossy and
lossless formats strictly separate. Also, lossy compression is complex to implement.
Adding JPEG support to a PNG decoder might increase its size by an order of magnitude.
This would certainly cause some decoders to omit support for the feature, which would
destroy our goal of interchangeability.
There is no support for CMYK or other unusual color spaces. Again, this is in the name of
promoting portability. CMYK, in particular, is far too device-dependent to be useful as a
portable image representation.
There is no standard chunk for thumbnail views of images. In discussions with software
vendors who use thumbnails in their products, it has become clear that most would not use
a "standard" thumbnail chunk. For one thing, every vendor has a different idea of what the
dimensions and characteristics of a thumbnail ought to be. Also, some vendors keep
thumbnails in separate files to accommodate varied image formats; they are not going to
stop doing that simply because of a thumbnail chunk in one new format. Proprietary chunks
containing vendor-specific thumbnails appear to be more practical than a common thumbnail
format.
PNG also does not support multiple images in one file. (Note: TIFF does).
It is worth noting that private extensions to PNG could easily add these features. They
are not, however, included as part of the basic PNG standard.
"Wayne Fulton" <nospam@invalid.com> wrote in message
news:i5ednWqSaJ3UW-jd4p2dnA@august.net...
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