[photodesk] Re: Saving 24b Sprites with mask in 3.06

  • From: Gavin Crawford <gav@xxxxxxxxxxxxxxxxxxxx>
  • To: photodesk@xxxxxxxxxxxxx
  • Date: Fri, 23 Jun 2006 14:27:51 +0100

In article <gemini.j1b9on032qfgt01x8.druck@xxxxxxxxxxxx>,
   David J. Ruck <druck@xxxxxxxxxxxx> wrote:
> Gavin Crawford <gav@xxxxxxxxxxxxxxxxxxxx> wrote:

> > Photodesk 3.06 no longer seems to include any mask data when saving a
> > 24bit RGB sprite. It works as expected when saving a CMYK sprite.
> > 
> > Anyone know how I can change Photodesk so it saves the mask for RGB
> > sprites. It used to work fine in 3.03.


> Now the question is, did versions up to 3.03 also generate a compatible
> 1bpp mask?

Yes it does here.

> I can't check now as I dont have any old copies with me, but
> I recall Photodesk has always dones this bending of the sprite format
> rules to preserve the full alpha channel. If anyone wants to test it,
> create a masked 24bpp sprite in !Paint, save it, load it in to
> Photodesk 3.03 and resave as a different name and check the file
> lengths. If it preserved the mask, they will be the same size, if not
> the Photodesk one is approx 1/32th smaller.

When saving as an RGB sprite: in 3.03 the the 8bpp alpha data is
converted to standard 1bpp mask data and is visible in !Paint.

I did your test and created a small 24bpp sprite with mask in !Paint
which was 165,656 bytes. After loading and resaving in 3.03 the byte
count is the same, and the sprite has a standard 1bpp mask and the 8bit
alpha data is not saved within the saved file.

However, in 3.06 it is as Dave describes and the file size is 160,056
bytes (5,600 bytes smaller) and no mask is visible in !Paint.

So I take it that the change between versions is an internal code change
and not something I can alter in any configuration options?

I'm not sure I agree with this change of action between 3.03 and 3.06!
AFAICR in the older versions such as 3.03 the alpha channel that would
be used as the Sprite's 1bp mask was selectable via the channels window
and controlled by which alpha channel had it's eye icon selected.
Therefore, no eye icon selected would create a 24b sprite with no mask.

To me, it seems a bit silly that this action of saving the 8bit alpha
data in the unused byte portion of the sprite format isn't an option.
I don't see that there is much point in saving this alpha data in the
sprite format if Photodesk is the only application the recognises it. If
you need to preserve the full editing capabilities of the file then
surely saving as a TIFF with Alpha data and Auxiliary data is the
correct method? And by not having the option of saving the RGB
sprite with a standard mask, Photodesk can no longer be used as a means
of converting images to a valid sprite format.

I also see it as being odd that the RGB sprite saving doesn't match the
saving of a CMYK sprite, in that the CMYK sprite converts the alpha data
to a standard 1bpp mask.

I'm not sure if the new Photodesk maintainer reads this list, but if so,
and you are reading this  - any chance of an option to switch it back to
the old method if desired.

Gavin Crawford
email: gav@xxxxxxxxxxxxxxxxxxxx
  web: www.crawford-print.co.uk

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