Transparent Color Problem

[Christopher MacLeod]

Sometimes when I use the "transparent color" tool in Mac's PowerPoint 2008
to remove the background from a JPG image, the removal doesn't remain
transparent when the slide presentation is opened in a PC's PowerPoint 2003.

I tried to outsmart the problem by using "transparent color" in the PC's
PowerPoint. But when I returned the file to the Mac, the background color
had returned.

Part of the mystery for me is that, as I said, the problem occurs only
sometimes, and I can't pinpoint a difference in the nature of the images or
in the way they are placed onto a slide. Most of my image manipulation takes
place in Photoshop Elements 8. Sometimes I place images onto a blank area of
a slide; other times, I place them into "content placeholder."

Any help would be appreciated.

 

[Jeff Chapman]

Hello Christopher,

Sometimes when I use the "transparent color" tool in Mac's PowerPoint 2008
to remove the background from a JPG image, the removal doesn't remain
transparent when the slide presentation is opened in a PC's PowerPoint 2003.

I tried to outsmart the problem by using "transparent color" in the PC's
PowerPoint. But when I returned the file to the Mac, the background color
had returned.

Part of the mystery for me is that, as I said, the problem occurs only
sometimes, and I can't pinpoint a difference in the nature of the images or
in the way they are placed onto a slide. Most of my image manipulation takes
place in Photoshop Elements 8. Sometimes I place images onto a blank area of
a slide; other times, I place them into "content placeholder."

If you are using Photoshop Elements to edit your photos,
perhaps it is safer to add your transparency in Photoshop
Elements, and then save the files as PNG-8 or PNG-24
from Photoshop. That way, when you import them into
PowerPoint for Mac or for Windows, the transparency
should remain the same.

Jeff

 

[CyberTaz]

IMHO, Jeff has offered the best advice. In fact, *any* graphics editing is
best done using a program designed for the purpose rather than relying on
"convenience features" available in a different type of program.

The transparent color feature in PowerPoint designates one specific color to
be rendered as "transparent" based on values in a table of color values. The
values can differ from one version of the software, system & OS to another
since each has its own 'color space'. That difference is typically not
noticeable to the naked eye or in a printed copy, but the transparency
assignment is explicitly precise. IOW, if the color value rendered as
transparent in one scenario is interpreted as "fff032" but renders as
"fff031" on another system the transparency attribute isn't attached to it.

Regards |:>)
Bob Jones
[MVP] Office:Mac

 

[Christopher MacLeod]

Thanks for the responses, Jeff and Bob. I do use Photoshop Elements to
render unwanted backgrounds transparent, but this operation creates a
separate layer for the image that makes the saved image (JPG or PNG) much
larger. Flattening the image to reduce its size creates a neutral
background. Usually what I've done is to fill this background with some
shade or color that isn't duplicated elsewhere in the image. In that way,
when I insert the image onto a slide, I can make that background transparent
without wrecking the desired parts of the picture.

I know I'm starting to drift off topic here, but is there some sort of chart
that would allow me to compare how color values are rendered so that in
Photoshop Elements I could pick a color value that I'd be reasonably sure
would be rendered the same in the different environments?

Again, thanks.

Chris

 

[CyberTaz]

As you've found, Transparent Backgrounds in PhotoShop images do not
translate to "transparency". It requires an 'image clipping path' in order
for the peripheral area of the image to render transparent when the image is
placed in a document or presentation. I don't believe PE supports that
capability -- I think you'd need its big brother. I do appreciate your
clever attempt at a workaround, though

Unfortunately there is no such chart because there is no reliable standard
on which to base it... If there were the chart wouldn't be necessary. The
best suggestion I can offer is that when you make sure to select one of the
216 Web Safe RGB colors for your background fills in PE. That's the best
assurance that the color will be as "device independent" as possible.

HTH |:>)
Bob Jones
[MVP] Office:Mac

 

[Christopher MacLeod]

Thanks for the help, Bob. I may try selecting a web safe color as my first
step.

Chris

 

[Jeff Chapman]

Hello Christopher,

Thanks for the responses, Jeff and Bob. I do use Photoshop Elements to
render unwanted backgrounds transparent, but this operation creates a
separate layer for the image that makes the saved image (JPG or PNG) much
larger. Flattening the image to reduce its size creates a neutral
background.

JPEG/JPG files do not contain a transparency layer, so
they will have to be flattened anyway when outputted
from Photoshop Elements.

Usually what I've done is to fill this background with some
shade or color that isn't duplicated elsewhere in the image. In that way,
when I insert the image onto a slide, I can make that background transparent
without wrecking the desired parts of the picture.

I understand the technique that you're using, and have
done this myself in the past.

As you've probably found, PowerPoint's transparency color option
works well enough if you are using it on very basic images that
have large areas of solid color with sharp distinctions in color,
such as graphics.
However, the effect tends to produce rough-looking edges on photos
with gradual variations in color or soft edges.

The main (and evidently unavoidable) problem with using
transparency in photos and then importing them into PowerPoint is
that you are basically locked into one format: PNG. PNG is a fine format
overall for the web and general graphics, but PNG-8 only
gives you 256 colors to work with. In short, you won't get much
better results with the rough edges than you will with PowerPoint's
transparency feature.

PNG-24 will give you many more colors and much smoother
transparency options, at a significantly larger file size.
You may have to bite the bullet and bear with the larger file
sizes for the sake of a more professional-looking photo.

Are you outputting using the Save feature in Photoshop Elements,
or the Save for Web feature? Save for Web gives you far more
options and a smaller image to boot. It may not help at all
when working with PNG-24, though.

Also, to keep image sizes down, make sure that you are
sizing your images respective of the media and resolution you'll
use them in.
If you know that you are showing your presentation on a laptop
screen or a medium-size monitor and that it won't be printed,
you can and should resize your images in PS/PE to reflect that.
File sizes for PNG-24 still tend to be large, but at least
keeping the pixel size equal or close to the output resolution
will help matters.

Finally, you can adjust the color table and number of colors outputted
in PS/PE for PNG-8 files with transparency on the Save for Web
dialog, so for some images, a smaller PNG-8 file may look good
enough for your needs.

Jeff

 

[Christopher MacLeod]

Hi, Jeff,

Thanks for the quick lesson. I'll explore the possibilities of PNG formats;
I've never used PNG before.

For much of what I'm doing, the images are grayscale, usually quite high
contrast. What mystifies me is that some of the images remain transparent in
PowerPoint on either platform; others invariably lose their transparency
when shown on a PC. While I thought I was treating them all the same in PE,
I confess I wasn't paying close attention and was rather slapdash about the
matter.

Chris

 

[Jeff Chapman]

Hi Christoper,

For much of what I'm doing, the images are grayscale, usually quite high
contrast. What mystifies me is that some of the images remain transparent in
PowerPoint on either platform; others invariably lose their transparency
when shown on a PC. While I thought I was treating them all the same in PE,
I confess I wasn't paying close attention and was rather slapdash about the
matter.

I see... if you had been using grayscale images with
high contrast, then PowerPoint's transparency feature
may have looked all right in most situations.
I imagine you were using it to knock out the background
or the likes. If the background is solid white and
the object in the image or illustration itself does not
contain white, then the results probably looked OK
to you for the most part.

Come to think of it, I have seen some issues where
images lose transparency back when I was working with
PPT for Windows only. It might have been when I opened
certain presentations from 2000 format in PPT 2002 or 2003.
I can't quite put my finger on it.
Anyway, suffice to say that if you are working cross-
platform, your best bet is to use either GIF or PNG
with transparency, and add the transparency in using
Photoshop Elements, before importing them into PowerPoint.
The benefit to this workflow is that you will be able
to reuse those images in another application and still
retain the transparency.

If you have any questions on how to use the
Photoshop Elements tools to create and save transparency,
feel free to post again.

Jeff