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I started another page with the same idea of the VFAQ page: The
common misunderstandings page. The intention of the page is to clear up
some common misunderstanings people have about computer related things
(mainly about topics related with povray, graphics, etc). The page has
only one entry right now, which is a very good example of what I mean.
Wrong allegations and correct information about them is very welcome.
I'll add a link to the page from the VFAQ page if/when I get some more
entries.
The page can be found at:
http://iki.fi/warp/misunderstandings/
--
main(i,_){for(_?main(i+1,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[--i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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My personal biggest pet peeve, which isn't about POVRay or Graphics is
when people ask..."Are you on the Internet" and they mean World Wide
Web. The Internet is so much bigger than just the Web that I want to
smack them one and point out what else is out there.
Steve
Nieminen Mika wrote:
>
> I started another page with the same idea of the VFAQ page: The
> common misunderstandings page. The intention of the page is to clear up
> some common misunderstanings people have about computer related things
> (mainly about topics related with povray, graphics, etc). The page has
> only one entry right now, which is a very good example of what I mean.
> Wrong allegations and correct information about them is very welcome.
> I'll add a link to the page from the VFAQ page if/when I get some more
> entries.
> The page can be found at:
>
> http://iki.fi/warp/misunderstandings/
>
> --
> main(i,_){for(_?main(i+1,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[--i]
> ):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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<HTML>
So which formats are better than the other?
<BR>If you had to use a scale of 1 - 10 ...is png better than jpeg, gif
etc.
<BR>I assume the bitmap is the best, or maybe not...you tell me.
<P>--
<BR>...coffee?...yes please! extra sugar,extra cream...Thank you.
<BR> </HTML>
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> So which formats are better than the other?
> If you had to use a scale of 1 - 10 ...is png better than jpeg, gif
> etc.
> I assume the bitmap is the best, or maybe not...you tell me.
There is no perfect format, although I find the 'best' format for me is
PNG.
Allow me to ellaborate a bit on graphics files. There are 5 main
compression tecniques used in graphics files:
Run Length Encoding (RLE): lossless. Supported by Photoshop and TIFF
file formats and some common Windows file formats.
Lemple-Zif-Welch (LZW): lossless. Supported by TIFF, PDF, GIF, and
PostScript language file formats. It's good for compressing images that
contain large areas of a single color, like screenshots or simple paint
images.
Joint Photographic Experts Group (JPEG): lossy. Supported by JPEG, PDF,
and PostScript language file formats. JPEG compression provides the best
results with continuous-tone images, such as photographs.
CCITT: lossless. It is mainly for black-and-white images. Supported by
the PDF and PostScript language file formats.
ZIP: lossless compression technique supported by the PDF file format.
Like LZW, ZIP compression is best for images that contain large areas of
single color.
These are the main formats used in graphics (at least in the POV world).
BMP: the standard Windows image format on DOS and Windows-compatible
computers. The BMP format supports RGB, indexed-color, grayscale, and
Bitmap color modes, and does not support alpha channels. You can specify
For 4-bit and 8-bit images using Windows format, you can also specify
RLE compression.
GIF: or Graphics Interchange Format, is the file format commonly used to
display indexed-color graphics and images in hypertext markup language
(HTML) documents over the World Wide Web and other online services. GIF
is a LZW-compressed format designed to minimize file size and electronic
transfer time. The GIF format does not support alpha channels.
Toaster and transferring files to and from the Commodore Amiga system.
In addition, this format is supported by a number of paint programs on
DeluxePaint from Electronic Arts. The IFF format supports RGB,
indexed-color, grayscale, and Bitmap color modes, and does not support
alpha channels.
JPEG: or Joint Photographic Experts Group format is commonly used to
display photographs and other continuous-tone images in hypertext markup
language (HTML) documents over the World Wide Web and other online
services. The JPEG format supports CMYK, RGB, and grayscale color modes,
and does not support alpha channels. Unlike the GIF format, JPEG retains
all color information in an RGB image but compresses file size by
selectively discarding data. A higher level of compression results in
lower image quality, and a lower level of compression results in better
image quality. In most cases, maximum quality produces a result
indistinguishable from the original.
PCX: commonly used by IBM PC-compatible computers. Most PC software
supports version 5 of the PCX format. A standard VGA color palette is
used with version 3 files, which do not support custom color palettes.
The PCX format supports RGB, indexed-color, grayscale, and Bitmap color
modes, and does not support alpha channels. PCX supports the RLE
compression method. Images can have a bit depth of 1, 4, 8, or 24.
PNG: developed as a patent-free alternative to GIF, the Portable Network
Graphics (PNG) format is used for losslessly compressing and displaying
images on the World Wide Web. Unlike GIF, PNG supports 24-bit images and
produces background transparency without jagged edges; however, some
older versions of Web browsers may not support PNG images. The PNG
format supports grayscale and RGB color modes with a single alpha
channel, and Bitmap and indexed-color modes without alpha channels. PNG
uses the saved alpha channel to define transparency in the file.
board and is commonly supported by MS-DOS color applications. The Targa
format supports 32-bit RGB files with a single alpha channel, and
indexed-color, grayscale, and 16-bit and 24-bit RGB files without alpha
channels.
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I would call this one of the BIG misconceptions, that there is a "best"
format (or a "best" graphics programs, or, "best" computer, or,.....). Like
most things in life there is no best way. There is only a most appropriate
trade off depending on circumstances. In other words, it depends on what you
want to use the file for. Try to learn what the properties
(colour depth, compression, compatibility,...) of the different file types
are and then make a decision in each case as to what suits best.
Sorry if that sounds like a rant, but this is something I battle every day
working an a Help Desk.
Regards
Gordon
Phil Clute wrote in message <36E81BB3.1250B1D2@tiac.net>...
So which formats are better than the other?
If you had to use a scale of 1 - 10 ...is png better than jpeg, gif etc.
I assume the bitmap is the best, or maybe not...you tell me.
--
...coffee?...yes please! extra sugar,extra cream...Thank you.
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<HTML>
Thanks Anthony, that was educational.
<P>--
<BR>...coffee?...yes please! extra sugar,extra cream...Thank you.
<BR> </HTML>
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Just a small error correction. PNG does support alpha channels
in index-color mode. The alpha values can be stored in the
palette. (Read it yesterday in a libpng example file)
/ Mathias
Anthony Bennett wrote:
> PNG: developed as a patent-free alternative to GIF, the Portable Network
> Graphics (PNG) format is used for losslessly compressing and displaying
> images on the World Wide Web. Unlike GIF, PNG supports 24-bit images and
> produces background transparency without jagged edges; however, some
> older versions of Web browsers may not support PNG images. The PNG
> format supports grayscale and RGB color modes with a single alpha
> channel, and Bitmap and indexed-color modes without alpha channels. PNG
> uses the saved alpha channel to define transparency in the file.
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Anthony Bennett <ben### [at] panama phoenixnet> wrote:
: board and is commonly supported by MS-DOS color applications. The Targa
: format supports 32-bit RGB files with a single alpha channel, and
: indexed-color, grayscale, and 16-bit and 24-bit RGB files without alpha
: channels.
Targa supports also compression. Can you specify which kind of compression?
--
main(i,_){for(_?main(i+1,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[--i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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Suggestions for additional topics include:
1. Why raytracers cannot do caustics :
I spent probably 10 hours experimenting with Corel Dream3D trying to get
caustics in an underwater scene by placing refractive, bumpy glass things in
front of my light source. I was cursing the shareholders of Corel Corp when
I just didn't understand raytracing.
2. Why raytracers cannot make a "homemade" spotlight:
When I first got POV, I probably spent about 10 hours trying to make my own
spotlight with a reflective surface on a parabolic shape and a point light
source in it. Again, I didn't understand how raytracers worked...
3. Explain compression in the MPEG format by giving exhaustive examples.
This is probably a bit more work, but is still a slight source of confusion.
Nieminen Mika wrote:
> I started another page with the same idea of the VFAQ page: The
> common misunderstandings page. The intention of the page is to clear up
> some common misunderstanings people have about computer related things
> (mainly about topics related with povray, graphics, etc). The page has
> only one entry right now, which is a very good example of what I mean.
> Wrong allegations and correct information about them is very welcome.
> I'll add a link to the page from the VFAQ page if/when I get some more
> entries.
> The page can be found at:
>
> http://iki.fi/warp/misunderstandings/
>
> --
> main(i,_){for(_?main(i+1,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[--i]
> ):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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On Fri, 12 Mar 1999 08:43:46 -0500, Greg M. Johnson <@aol.com> wrote:
>Suggestions for additional topics include:
>
>1. Why raytracers cannot do caustics :
>2. Why raytracers cannot make a "homemade" spotlight:
These are, of course, both the same topic. Clearly one would need
to start with a definition of caustics.
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