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Re: Conversion floating point to byte or integer [message #56316 is a reply to message #56315]

Thu, 11 October 2007 06:20

beardown911
Messages: 21
Registered: March 2007

Junior Member

On Oct 11, 1:08 am, "Jean H." <jghas...@DELTHIS.ucalgary.ANDTHIS.ca>
wrote:
>>> So what do you want to do with values greater than 255?
>
>>> You could do
>>> 1) compute your new image as a float,
>>> 2) scale everything down so ALL of your values are between 0 and 255 and
>>> save the image
>>> or 2) brightPixels = where(image gt 255)
>>> image[brightPixels] = 255 and save the image
>
>> Jean,
>
>> Thank you for your prompt reply and 2) is what I wanted.
>> Could I ask why this happen? Am I asking too basic question about
>> programming?
>
> So you need to scale it, not to typecast it.
> In IDL, if you typecast to byte, it does "wrap around" values, so that
> 255 is followed by 0...
> IDL> print, byte(256)
> 0
> IDL> print, byte(256+257)
> 1
>
> if you scale it using BytScl(), it takes the smallest value and assign
> it to 0, the max value to 255, and the result is a byte array
> IDL> print, bytscl([250,251])
> 0 255
>
> Jean
>
>
>
>> I casted output format to bytarr(cols, rows) to scale everything down
>> 0-255, but result was same.
>> I've read variables part in Liam's book, and tried the least
>> significant 8 bit extraction.
>> That doesn't seem to be the answer.
>
>> Well, thank you again.
>> Kim- Hide quoted text -
>
> - Show quoted text -

Jean,

Thanks a lot.

Kim

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[Message index]

		Re: Conversion floating point to byte or integer By: beardown911 on Thu, 11 October 2007 18:44
		Re: Conversion floating point to byte or integer By: M. Katz on Thu, 11 October 2007 14:04
		Re: Conversion floating point to byte or integer By: beardown911 on Thu, 11 October 2007 06:22
		Re: Conversion floating point to byte or integer By: beardown911 on Thu, 11 October 2007 06:20
		Re: Conversion floating point to byte or integer By: Maarten[1] on Thu, 11 October 2007 01:05
		Re: Conversion floating point to byte or integer By: Jean H. on Wed, 10 October 2007 23:08
		Re: Conversion floating point to byte or integer By: beardown911 on Wed, 10 October 2007 21:20
		Re: Conversion floating point to byte or integer By: Jean H. on Wed, 10 October 2007 16:44

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