To WAMUGGERS,
When I rotate the image in a JPEG file, the file size reduces from
the size received from the camera.
This occurs (to differing degrees) with Preview, Adobe Photo Deluxe,
Photoshop Elements and Canon Image Browser.
Can any one tell me why this happens and if the resulting image may
have degraded?
File sizes of 750Kb go to 350 - 470Kb.
Using iMac G5 20"
Unless you're using software that supports lossless image rotation
the image is being recompressed, hence the change in file size and
presumably quality (repeated rotations and saving will lead to
increased degradation in quality) I think iPhoto and GraphicConverter
both support lossless JPEG rotation.
JPEG is a lossy format, it throws away some image data and makes some
small approximations (hopefully within a range that's imperceptible
to humans) to allow for good compression. This is what the 'quality'
rating is when you're saving a JPEG. This is usually visible near the
edges of objects in the image (this is why it's a bad idea to save
images of text as JPEG, as there are lots of fine edges). Other
formats such as TIFF, PNG or GIF are lossless, they maintain the
image's pixels exactly, but have larger file sizes.
Have fun,
Shay
--
=========================== Shay Telfer ================================
Perth, Western Australia Technomancer The love of liberty is the love
Opinions for hire [POQ] of others; the love of power is
http://public.xdi.org/=Shay fnord the love of ourselves - Hazlitt
