Rotate image changes image proportions

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Guest

In all the image editors I have installed (including Microsoft Photo Editor
and Adobe Photoshop LE) when I rotate an image 90 degrees left or right, the
image resizes, so that for example a 9 x 9cm square becomes a 9.9 x 8.4
rectangle. Any ideas why this might be? Thanks.
 
Ian said:
In all the image editors I have installed (including
Microsoft Photo Editor and Adobe Photoshop LE) when I
rotate an image 90 degrees left or right, the image
resizes, so that for example a 9 x 9cm square becomes a
9.9 x 8.4 rectangle. Any ideas why this might be?
Thanks.
Click to expand...
===========================
I would suspect that you have an issue
with your video driver. Might be worth
a try to search the website of your video
adapter's mfg. for an updated driver.

--

John Inzer
MS Picture It! MVP

Digital Image
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This has to be an aspect setting, not a driver issue. Video drivers
shouldn't affect image manipulation and calculations in memory, only
the actual displaying of images.

It seems likely that it's assuming the image pixels are non-square, so
that rotating the image either requires changing the pixel dimensions
to keep the displayed/printed image square, or keeps pixel dimensions
unchanged but causes the physical dimensions to change. On a 320x200
VGA display, for example, a 120x100 pixel image is square. Rotate it to
a 100x120 pixel image and it's now wider than tall, so its dimensions
in cm will no longer be square. Likewise, if you kept those dimensions
square the image would remain 120x100, but what had been the horizontal
dimension would have been sampled down and what had been the vertical
dimension would have been sampled up. If the image was displayed with
square pixels and had shown a circle between 10-pixel-wide borders, it
would now show a somewhat squashed ellipse with 8 or so pixel high
borders above and below.
 
I can't duplicate this phenomenon with Photoshop or MS picture viewer.
Describe the technique you're using.
 
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