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Re: JPEG2000 compression [message #43467 is a reply to message #41151]

Wed, 13 April 2005 09:24

Rick Towler
Messages: 821
Registered: August 1998

Senior Member

Roberto Monaco wrote:
> I have a question regarding JPEG2000:
>
> How do you control compression ratio when you save an image as JPEG2000
> using the IDL object?

Looks like the N_LEVELS property.

> The following is curious: within a Photoshop plug-in I use to save JPEG2000
> images, "they" define a compression factor. If I save the same image with
> different compressions ratios (e.g. 1:1, 1:10, 1:40) I obviously get big
> differences in the resulting file sizes. But if you read these files into
> IDL objects, surprisingly all properties are exactly the same!! Same
> dimensions for the data array, same bit_depth, same number of layers, etc.
> ?? This does not make any sense to me ... I must be overlooking at something
> stupid?

Well, I know nothing about JPEG2000 but I would hope that all of the
properties that you have specified *would* be identical. The only
property that should change would be the compression factor. Don't know
where that would be though. Maybe the N_LEVELS property again? Don't
know if that would be set after reading a file or if it only applies to
writing.

-Rick

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[Message index]

		JPEG2000 compression ratios? By: Matt Feinstein on Wed, 29 September 2004 05:14
		Re: JPEG2000 compression By: Emmanuel Christophe on Thu, 14 April 2005 07:41
		Re: JPEG2000 compression By: Rick Towler on Wed, 13 April 2005 16:27
		Re: JPEG2000 compression By: Roberto Monaco on Wed, 13 April 2005 12:55
		Re: JPEG2000 compression By: Rick Towler on Wed, 13 April 2005 09:24

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