Reduce image quality (and file size)

Question

Is there a simple way to reduce the quality of all backgroung
images ? (there are all bitmap images, about 3 MB each of them)
I imagine that by reducing the image quality, the file size
will be less huge...
But I wasn't able to find a way to do that...
(the option about JPEG quality in project/preferences has no
effect, because all background images are bitmap... )
Any idea is welcome !
Valérie

Answer 1

Hi Valerie
I have been doing some research on this -- the issue of file
size (relating to both .cp and .swf) crops up a lot on this forum,
so I wanted to find out which were the critical factors relating to
images.
My findings show that there are two critical factors:
-- Slide Properties: Quality (High, Standard, JPEG,
Optimized)
-- Format of original image file (used for slide background
or inserted image object)
To summarize the results of my testing:
Slide Quality
Changing the slide quality from High
to Standard or JPEG makes little or no difference to the size of
the .cp file but can *significantly* reduce the size of the
.swf
This is an especially useful way of
dealing with the very large .swf file sizes caused by importing PPT
slides
A .swf consisting entirely of
imported PPT slides with complex backgrounds may be reduced to less
than 10% of its original size by changing the quality setting for
each of the slides to JPEG and using a JPEG image quality setting
of 75%.
Format of original image file
For complex images such as photos,
the best image file format to use is (oddly) .bmp -- although it
results in a larger .cp file than other file formats (such as .jpg
or .png), it generates the smallest .swf output.
The benefit of using the .bmp format
is less marked if you have set slide quality to Standard instead of
High, but it can still cut the file size of the .swf output by up
to 50%
For slides using a quality setting of
JPEG, there appears to be no difference in resulting .swf file size
between .bmp or any other image file format
A final comment: it is interesting to compare the size of the
.cp and resulting .swf for different Captivate projects. There is
typically an assumption that the .swf file will be smaller due to
compression. However, this is not always the case. For example, I
tested one project that used High slide quality and images that had
been inserted from .jpg files -- the generated .swf file was over 4
times larger than the .cp file. However, when I changed the quality
setting for all slides to JPEG, the .swf file reduced to less than
50% of the size of the .cp file.
I hope this information is helpful -- please contact me if
you'd like to see the detailed test data.
Best regards,
-Matthew Ellison