What is compress actually doing?
There are many possible ways to compress a picture file, and different
graphics formats and applications use different ones.
Reducing the resolution is one of them (one that looses information),
reducing the color depth (number of allowed colors) could be another.
If the bitmap was uncompressed before, it can be compressed without any loss
by storing it more efficiently.
Say in a black-and-white picture, you don't need to store the information
that a whole line of say 1000 pixels is white by storing the number for
"white" 1000 times (1000 numbers), you can instead store the number for
white and that there's a run of 1000 such pixels (2 numbers).
There are clever ways to do that (both lossy and lossless) like the ones
used in JPEGs, which basically don't store the pixel colors themselves, but
the parameters for an algorithm to recreate them.
Klaus
"Terry Farrell" wrote:
Compress changes the resolution. If you click on Compress, Options, you
can choose between Print 220ppi, Screen 96 ppi or email 72 ppi. (This is
for Word 2007: other versions are slightly different.)
--
Terry Farrell - MSWord MVP
"John" wrote in message
...
Problem: What is compress actually doing?
Word 2007
XP Pro SP2
If you compress the images in a DOC file using Format Pictures... |
Picture tab | Compress button, the following happens:
The file becomes smaller.
The printed page looks the same.
The screen image looks the same.
What actually changed?
Is it the Resolution in DPI?
Is it the Dimension in Pixels?
Changing the Resolution in DPI should only change the physical size of how
something prints. It does not change the number of pixels in the image
itself.
Changing the Dimension in Pixels would cut off part of the image, or
it could do an algorithmic shrink where there are less Dimension in Pixels
so you see the same image but using fewer Dimension in Pixels. I
appreciate your feedback.
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