[projectaon] Re: PNGout
- From: "David Davis" <feline1@xxxxxxxxxxxxx>
- To: <projectaon@xxxxxxxxxxxxx>
- Date: Thu, 24 Apr 2008 11:36:00 +0100
Having one of the colour management chunks (even for black & white drawings)
is no bad thing, probably, as it can help ensure the black & white points
are
rendered correctly? (rather than the whole thing going sepia, for
instance) -
not sure what the most efficient PNG chunk for that would be off the top of
my head.
A text chunk could, in principle, have the same "alt text" that we put into
the HTML,
which a clever program could use for the visually impaired etc ...
whether or not there's any software which ever actuall does this, I wouldn't
know.
It can also be used to store a simple copyright statement or the name of the
illustrator. Again, this is formally a Nice, Right and Propper thing to do,
but
it may be in actual practice be completely pointless ;)
----- Original Message -----
From: "Robert Wellock" <xhtmlcoder@xxxxxxxxx>
To: <projectaon@xxxxxxxxxxxxx>
Sent: Thursday, April 24, 2008 11:24 AM
Subject: [projectaon] Re: PNGout
To clarify; GIF does NOT support truecolor images, alpha channels, or
gamma correction in the first place.
PNGOUTWin doesn't affect the "Standard Chunks" by 'Default' it only
concerns itself with the "Ancillary Chunks", for example:
bKGD - background color - specifies a default background colour to
present the image against.
pHYs - encodes the absolute or relative dimensions of pixels, e.g. aspect
ratio.
gAMA - specifies the gamma of the camera (or simulated camera).
cHRM - is allowed in all PNG files, although it is of little value for
greyscale images.
iCCP - ICC profile.
sRGB - cross system colour fidelity.
sBIT - sample depths.
sPLT - suggested-palette chunk.
hIST - histogram is nothing more than a frequency-of-occurrence table.
tiME - timestamp.
iTXt - international text Annotations.
tEXt - textual data, keyword or the text string.
zTXt - compressed textual data.
As you can see most of them would be overkill in PNG-8, e.g. bKGD,
tiME, iTXt, tEXt, zTXt for the Internet Editions. The "equivalents"
weren't already present in the GIF specifications anyway so all-in-all
if it weren't there it cannot have been lost.
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