How does PowerPoint convert an image?

[Steve Jones]

Hello. I use ppt to display images I generate during my work in forensic
imaging when I appear in court. Our imaging processes focus on the use of
lossless compression. Some time back I did an experiment where I inserted 5
images, one per slide, into a ppt file. Each image was about 1MB so I
expected the resulting ppt to be slightly larger than that but found the file
to actually be less than 2 MB. I did some research and found that it may
have something to do with ppt converting the raster image into a vector
graphic or something. Can someone provide me with a 'scientific' explanation
or direct me to a White Paper or something similar?

Thanks in advance,

 

[TAJ Simmons]

Steve,

Each image was about 1MB

What filetype were they (e.g. BMP JPG GIF etc)

Cheers
TAJ Simmons
microsoft powerpoint mvp

awesome - powerpoint backgrounds,
http://www.awesomebackgrounds.com
free powerpoint templates, tutorials, hints and tips etc

 

[Steve Jones]

We deal with TIFF images. I got the info on the vector conversion from
someone in the PowerPoint developers group. I have been told the same thing
from someone at Noritsu ( makers of our mini-lab) and a sales person for
Raster Plus. We use the Photo Album feature for some applications while for
others we use Image>Insert.

 

[Echo S]

What PowerPoint developers group?

I'm pretty sure PPT doesn't convert raster graphics to vector. ISTR that it
may store raster graphics internally as PNG. PNG is a lossless format.

 

[Steve Jones]

When I discovered the reduction in the anticipated file size after importing
the images through different ways, I contacted Microsoft and was put through
to someone in their PowerPoint group. I forget the exact title for the
individual but he was a Microsoft employee who, from what I understood,
worked with those who develop the new versions of software. I will see if I
can dig up more info on him.

He did say that PowerPoint did some type of conversion but PNG was not what
he said. He said it was like a vector graphic of some type.

I will hunt for some of the info and post it.

 

[Steve Jones]

I just spoke with someone at the Microsoft Help Desk and they will not
process my question until I pay a fee. My boss feels that this issue is
Microsoft's, not ours, and is not willing to front the money. As it sits
now, I am unable to bring this up with the engineers.

 

[Steve Jones]

oops...that should have read Insert>Picture>From File

We deal with TIFF images. I got the info on the vector conversion from
someone in the PowerPoint developers group.

What specific information? "something to do with ppt converting ..." is pretty
vague.

I have been told the same thing
from someone at Noritsu ( makers of our mini-lab) and a sales person for
Raster Plus.

We use the Photo Album feature for some applications while for
others we use Image>Insert.

Where do you find that? There's no Image menu item in PowerPoint.
Perhaps some addin has added it to your PPT menu?

W/o knowing the specifics in the situation you're asking about, it's impossible to
offer any explanation.

 

[Echo S]

I guess I still don't know what the "issue" is.

If it's learning how PPT stores graphic images internally, then I guess we'd
need the specifics of what was said during this conversation:

And I don't know that we'll be able to shed any more light on this for you
than the MS person already did.

Browsing back through the rest of this thread, I see you mentioned that
you're inserting TIFFs. I'd still be very surprised if PPT converted a
raster-based TIF to something vector-based like WMF or EMF, but it may
depend on if you were talking about inserting the TIFs via the Photo Album
thing or if you were talking about using Insert/Picture/From File.

 

[Steve Jones]

I guess I am looking for a confirmation that it is indeed converting it to a
PNG. After importing 5 x 1MB pictures, the ppt file is less than 2 MB. We
use lossless processing when dealing with all our forensic images. Once we
get to PowerPoint, the files are smaller than anticipated. Is PNG such an
effiencient format that it can losslessly store the images in files 50%
smaller than the TIFF?

I guess I still don't know what the "issue" is.

If it's learning how PPT stores graphic images internally, then I guess we'd
need the specifics of what was said during this conversation:

And I don't know that we'll be able to shed any more light on this for you
than the MS person already did.

Browsing back through the rest of this thread, I see you mentioned that
you're inserting TIFFs. I'd still be very surprised if PPT converted a
raster-based TIF to something vector-based like WMF or EMF, but it may
depend on if you were talking about inserting the TIFs via the Photo Album
thing or if you were talking about using Insert/Picture/From File.

--
Echo [MS PPT MVP]
http://www.echosvoice.com

I just spoke with someone at the Microsoft Help Desk and they will not
process my question until I pay a fee. My boss feels that this issue
is Microsoft's, not ours, and is not willing to front the money. As
it sits now, I am unable to bring this up with the engineers.

 

[Echo S]

http://www.scantips.com/basics09.html and especially the PNG-specific
information at http://www.scantips.com/basics9p.html should help explain
PNG. It is a very efficient format, yes.

I'm sorry, though -- I can't confirm that PPT is converting the TIFs to PNG
internally. I'm pretty sure that's what I've been told by the PPT product
group, but I'm not 100% positive. Perhaps someone else will know for sure.

 

[Echo S]

If you Publish to HTML, you get the original images *as held within
PPT itself*. That's one way to see what's become of your TIFFs.

ooooh, yeah! What was I thinking?

FWIW, I slapped a TIF and a PNG onto a blank slide (PPT 2003) and saved as
HTML.

I got a WMF preview of the slide, the TIF came out as both a PNG and a JPG,
and the PNG came out as both a PNG and a GIF.

If I change the publish settings to not be compatible clear back to IE 4.0,
then I only get the PNG images in the resulting files. The JPG and GIF are
just so the earlier versions of IE can display them.