Re: [CinePaint] Really basic script for batch converting.

On Wed, 25 Nov 2009 12:39:31 -0000 (GMT)
[email protected] wrote:

> 
> Ok, so is dithering only used for going from high bit depth to lower? Is
> the noise I'm adding after conversion 'dithering' or just damaging the
> image?
> 

The noise you are adding is only decreasing the number of pixels of
a certain value and spreading the difference by increasing the number
of pixels that are close to the original value.  For example, if you
have 1000 pixels of values of value 32000, after adding noise you will
have maybe 500 @32000 and 50 @32002, 50 @32004, 50 @31998, etc.  The
exact change depends on the type of noise that is added (gaussian,
laplacian, poisson) and the parameters for each type.

My view is that this will accomplish little for just a conversion
to higher bits.  If it helps out with subsequent processing I really
cannot comment.  But as you have seen it can degrade the original image.

> 
> I think this is what I'm driving at 'become more resistant to banding /
> compress'. The intention with these video image frames is to do quite
> strong colour correction/grading before encoding back to video codecs. It
> seems to do what I'm aiming for (whether that is correct or not) I've been
> able to do quite heavy handed HSL and curve adjustments and still have
> solid smooth histogram at the end of it. But I still have to take this
> through to the final sharpened encoded video files for final playback, I
> may find the noise has caused problems.
> 

I am not familiar with your source material, but in my own experience
I have found that it may not be possible to completely automate the
processing of a large series of images.  I have tried to implement
scripted processing but my results were never uniform or even predictable.
I've always had to bite the bullet and process each image individually
by hand.  But maybe your sources are similar enough to allow automation.

In any case, too many cooks spoil the broth, as the saying goes.
I would suggest to just experiment and accept the best method.

Frank Peters

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