Is there a lib which support .jpeg file with "RGBA" mode?

[google12]

hi,

May anyone help me?

I need a lib which support .jpeg file with RGBA mode. PIL seems to support
RGB and CMYK mode only...

Thanks for your help.

[Fredrik Lundh]

"google12" wrote:

May anyone help me?

I need a lib which support .jpeg file with RGBA mode. PIL seems to support
RGB and CMYK mode only...

last time I checked, JPEG didn't support RGBA.

</F>

[google12]

Oh, sorry. I made a mistake...

My question is -- when I run the code described below, the transparence of
the orginal image will be removed. How can I keep the transparence?

im = Image.open(test.png)
fp = open('test.jpg','wb')
im.save(fp,'JPEG')

"Fredrik Lundh" <fr*****@pythonware.com> ¦b¶l¥ó
news:ma*************************************@pytho n.org ¤¤¼¶¼g...

"google12" wrote:

May anyone help me?

I need a lib which support .jpeg file with RGBA mode. PIL seems to support RGB and CMYK mode only...

last time I checked, JPEG didn't support RGBA.

</F>

[Mike C. Fletcher]

google12 wrote:

Oh, sorry. I made a mistake...

My question is -- when I run the code described below, the transparence of
the orginal image will be removed. How can I keep the transparence?

im = Image.open(test.png)
fp = open('test.jpg','wb')
im.save(fp,'JPEG')

I believe the thrust of Fredrik's post was: you can't. JPEG does *not*
store alpha channels. It's just not part of the format, so if you need
to store in JPEG format, you will not be storing the alpha channel in
the file.

If what you're asking is whether you can store the alpha data to a
separate file (as is done with programs such as 3DStudio Max), yes, that
can be done too:

import Image
i = Image.open( r'p:\OpenGLContext\tests\wrls\simple_texturergba.p ng' )
alpha = i.getdata( 3 )
i2 = Image.new( 'L', i.size, )
i2.putdata( alpha )
i2.save( r'p:\OpenGLContext\tests\wrls\simple_texturea.jpg' , 'jpeg' )

HTH,
Mike

_______________________________________
Mike C. Fletcher
Designer, VR Plumber, Coder
http://members.rogers.com/mcfletch/

[google12]

Ann... I had tried to use Photoshop 7 to save a .png file with transparency
as a .jpg file, and the transparency will be kept in the .jpg file.

Thus, I don't know why...

Thanks for your help.
"Mike C. Fletcher" <mc******@rogers.com> ???
news:ma*************************************@pytho n.org ???...

Oh, sorry. I made a mistake...

My question is -- when I run the code described below, the transparence of

the orginal image will be removed. How can I keep the transparence?

im = Image.open(test.png)
fp = open('test.jpg','wb')
im.save(fp,'JPEG')

I believe the thrust of Fredrik's post was: you can't. JPEG does *not*
store alpha channels. It's just not part of the format, so if you need
to store in JPEG format, you will not be storing the alpha channel in
the file.

If what you're asking is whether you can store the alpha data to a
separate file (as is done with programs such as 3DStudio Max), yes, that
can be done too:
>>> import Image
>>> i = Image.open( r'p:\OpenGLContext\tests\wrls\simple_texturergba.p ng' ) >>> alpha = i.getdata( 3 )
>>> i2 = Image.new( 'L', i.size, )
>>> i2.putdata( alpha )
>>> i2.save( r'p:\OpenGLContext\tests\wrls\simple_texturea.jpg' , 'jpeg' )

[Peter Hansen]

google12 wrote:

Ann... I had tried to use Photoshop 7 to save a .png file with transparency
as a .jpg file, and the transparency will be kept in the .jpg file.

If JPEG doesn't support transparency, then clearly that couldn't have happened,
or Photoshop uses a non-standard JPEG format.

Perhaps Photoshop "transparently" (no pun intended) saves the alpha data
to some other location, but magically restores it when you reload the .jpg?

(How have you confirmed that the data is really stored in the .jpg file
and not somewhere else?)

[Lonnie Princehouse]

Peter Hansen <pe***@engcorp.com> wrote in message news:<3F***************@engcorp.com>...

...
Perhaps Photoshop "transparently" (no pun intended) saves the alpha data
to some other location, but magically restores it when you reload the .jpg?

That pun was _clearly_ intentional.

[Fredrik Lundh]

Peter Hansen wrote:

google12 wrote:

Ann... I had tried to use Photoshop 7 to save a .png file with transparency
as a .jpg file, and the transparency will be kept in the .jpg file.

If JPEG doesn't support transparency, then clearly that couldn't have happened,
or Photoshop uses a non-standard JPEG format.

Perhaps Photoshop "transparently" (no pun intended) saves the alpha data
to some other location, but magically restores it when you reload the .jpg?

JPEG supports application-defined data segments ("app markers"), so Photoshop
may simply pack the alpha layer using a suitable lossless compression (predictor
plus zip?) and embed it inside the JPEG stream.

or they may ignore that fact that using lossy compression for alpha layers isn't
really a good idea...

if anyone can mail me a sample (or better, post a sample somewhere, and mail
me an URL), I can look into it.

</F>