Krita-Plugins 1.6.4

Hello,

I am happy to announce the release of Krita-Plugins with a
"dither" (aka color 
reduction) filter. Packages and sources are available at 
http://www.krita-plugin
s.org/ .

-- 
Cyrille Berger
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Cyrille,

> I am happy to announce the release of Krita-Plugins
with a "dither" (aka color 
> reduction) filter. Packages and sources are available
at 
> http://www.krita-plugin
s.org/ .

just curious -- does it support dithering 24 bits down to
15, 16 or 18 bits?
This is often needed to make graphics for mobile phones.
Also important: dithering to <=8 bits but choosing colors
only from the 
15/16/18 bits "palettes". This way, there's no
ugly colour shift when 
the device with the limited palette displays 8 bit images
(which usally 
use 256 distinct 24bit colors, not 256 disting 15/16/18 bit
colors).

.mm
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Hi,

On Monday 07 January 2008, Moritz Moeller wrote:
> > I am happy to announce the release of
Krita-Plugins with a "dither" (aka
> > color reduction) filter. Packages and sources are
available at
> > http://www.krita-plugin
s.org/ .
>
> just curious -- does it support dithering 24 bits down
to 15, 16 or 18
> bits?
It currently only support dithering to 8bit. The only export
filter that is 
capable of creating a palette from an image is PNG, and PNG
is limited to 
8bits palette. But there is nothing in the algorithm that
prevent to use 
bigger palette when have export filters which can work with
higher depth 
palette.

> This is often needed to make graphics for mobile
phones. 
What it is trully missing for use in mobile phones is the
possibility to 
use "custom palette" instead of automatically
generated ones.

> Also important: dithering to <=8 bits but choosing
colors only from the
> 15/16/18 bits "palettes". This way, there's
no ugly colour shift when
> the device with the limited palette displays 8 bit
images (which usally
> use 256 distinct 24bit colors, not 256 disting 15/16/18
bit colors).
I don't follow you :/ What do you mean by 15/16/18bits
palette ? "Downscale" 
the colors of the palette to 15/16/18 bits when searching
for the closest 
color ?

-- 
Cyrille Berger
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On Mon, Jan 07, 2008 at 09:33:53PM +0100, Cyrille Berger
wrote:
> On Monday 07 January 2008, Moritz Moeller wrote:
> > Also important: dithering to <=8 bits but
choosing colors only from the
> > 15/16/18 bits "palettes". This way,
there's no ugly colour shift when
> > the device with the limited palette displays 8 bit
images (which usally
> > use 256 distinct 24bit colors, not 256 disting
15/16/18 bit colors).
> I don't follow you :/ What do you mean by 15/16/18bits
palette ? "Downscale" 
> the colors of the palette to 15/16/18 bits when
searching for the closest 
> color ?

I think he talks about devices that eg. have a 6+6+6 bit
display, but are
displaying a standard indexed image. The palette of this
image should only
contain colors that actually look different on this device.

Additionally there is need to dither without involving
indexed images, eg.
when going from 8 bits per color to 6 bits per color. (This
is also done
with audio.)

bye,
Martin
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On Tuesday 08 January 2008, Moritz Moeller wrote:
> > It currently only support dithering to 8bit. The
only export filter that
> > is capable of creating a palette from an image is
PNG, and PNG is limited
> > to 8bits palette. But there is nothing in the
algorithm that prevent to
> > use bigger palette when have export filters which
can work with higher
> > depth palette.
>
> yep, but try displaying a PNG dithererd to 256 colors
chosen from 16.8
> millions on a device (e.g. a mobile phone) that can
only display 262144
> colors -- if it has smooth ramps you will likely get
horrible banding
> and ugly colors as the device clamps a color to the
next available one.
>
> A good feature for starters is hence to allow dithering
to 256 out of
> 32768/65536/262144 evenly distributed colors (as
opposed to 16.8 million
> evenly distributed ones).

Didn't think of that one :/ Currently there are five
generators of palettes:
* two "optimized palette" (working on 4bits or
5bits colors and which 
generates a palette which try to minimize the error, quiet
slow)
* two "most used colors" (either creating 8bits or
4bits colors palettes, 
which used the most frequent colors on the image)
* random

-- 
Cyrille Berger
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