Computer Graphics with Photoshop - Transparent Bitmap (BMP)

Author

Transparent Bitmap (BMP)

sandspider

2005-06-21, 7:15 pm

Hi All,
Nice triky question .
How can we save a image with transparency as a BMP .
This is for use as a visible watermark with Digimarc PictureMarc 2005
which is a image watermarking utility plugin for photoshop.

Thanks

RSD99

2005-06-21, 7:15 pm

The short answer is you can't.

The BMP file format does not "support" transparency.

IIRC: The only formats that are capable of saving transparency (otherwise
known as Alpha channel) ... that are in relatively common usage ... are

GIF
PNG
TIFF (recent variations)
TARGA

"sandspider" <info@sandspider.net> wrote in message
news:1119366236.721155.283820@g43g2000cwa.googlegroups.com...
> Hi All,
> Nice triky question .
> How can we save a image with transparency as a BMP .
> This is for use as a visible watermark with Digimarc PictureMarc 2005
> which is a image watermarking utility plugin for photoshop.
>
> Thanks
>

tacit

2005-06-21, 7:15 pm

In article <1119366236.721155.283820@g43g2000cwa.googlegroups.com>,
"sandspider" <info@sandspider.net> wrote:

> Nice triky question .
> How can we save a image with transparency as a BMP .

Step 1: You can't.

The BMP format does not support transparency.

--
Art, photography, shareware, polyamory, literature, kink:
all at http://www.xeromag.com/franklin.html

tacit

2005-06-21, 7:15 pm

In article <9sWte.773$kZ.476@trnddc02>, "RSD99" <rsdwla.NOSPAM@gte.net>
wrote:

> IIRC: The only formats that are capable of saving transparency (otherwise
> known as Alpha channel) ... that are in relatively common usage ... are
>
> GIF
> PNG
> TIFF (recent variations)
> TARGA

Alpha channels are not the only way to achieve transparency.

GIF doesn't use an alpha channel for transparency; instead, it
designates a color in the color look-up table as transparent.

PNG, TIFF, and Targa formats support alpha transparency.

EPS, TIFF, and (some varieties of) Scitex CT support clipping path
transparency.

--
Art, photography, shareware, polyamory, literature, kink:
all at http://www.xeromag.com/franklin.html

Nicholas Sherlock

2005-06-21, 7:15 pm

sandspider wrote:
> Nice triky question .
> How can we save a image with transparency as a BMP .

Some programs will treat a 32-bit bitmap as having an alpha channel, is
this what you mean? Right click on your layer's thumbnail, click "Select
layer transparency". Click the "Select" menu, click "Save selection...".
Save it as a new channel in your picture (Call it whatever you like, I
prefer "Alpha"). Save as bitmap, make sure "Alpha channels" is ticked.

This may be version dependant, I use PhotoShop CS.

Cheers,
Nicholas Sherlock

KatWoman

2005-06-21, 7:15 pm

but are any browsers configured to see the alpha in the 32 bit images?
Windows OS can see the transparency.
When I save Tiff with alpha channels Windows only "sees" the top
(adjustment ) layer. It can't see "through" to the rest of the image, of
course in PS they look fine and contain all the layers.

"Nicholas Sherlock" <n_sherlock@hotmail.com> wrote in message
news:d99tk9$htn$1@lust.ihug.co.nz...
> sandspider wrote:
>
> Some programs will treat a 32-bit bitmap as having an alpha channel, is
> this what you mean? Right click on your layer's thumbnail, click "Select
> layer transparency". Click the "Select" menu, click "Save selection...".
> Save it as a new channel in your picture (Call it whatever you like, I
> prefer "Alpha"). Save as bitmap, make sure "Alpha channels" is ticked.
>
> This may be version dependant, I use PhotoShop CS.
>
> Cheers,
> Nicholas Sherlock