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Re: transparent background [message #35358 is a reply to message #35296]

Thu, 05 June 2003 13:22

Rick Towler
Messages: 821
Registered: August 1998

Senior Member

"David Fanning" wrote in message..
> Rick Towler writes:
>
>> You didn't really fool around for 20 minutes, did you?
>
> Indeed I did. I thought it might take five. And now
> I've just spent another 15. :-)
>
>> With the B/W linear color table loaded:
>>
>> IDL> test = BYTARR(200,200)
>> IDL> test[100:199,*] = 200
>> IDL> tvlct, r,g,b,/get
>> IDL> write_png,'test.png',test,r,g,b,TRANSPARENT=[0]
>>
>>
>> In PP, Insert -> Picture -> From File... and select 'test.png'
>>
>> I have a 200x200 image, right half is lt. gray, left half is
transparent.
>>
>> Load test.png up in Photoshop and the left half of the image is
transparent
>> too.
>
> Well, I can see this works. But why doesn't my test
> program work?

It looks like WRITE_PNG only accepts "0" as a valid transparent pixel index
value. I can get your program to work if I load your background at 0 and
specify 0 as the transparent index but it will not work with any other
value. it looks like I was just lucky :)

Another annoying thing I noticed is that the VERBOSE keyword isn't verbose
at all. I didn't get any additional output with it set.

I would submit these as bugs.

-Rick

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[Message index]

		transparent background By: craigni on Tue, 03 June 2003 09:59
		Re: transparent background By: Rick Towler on Thu, 05 June 2003 13:22
		Re: transparent background By: David Fanning on Thu, 05 June 2003 13:03
		Re: transparent background By: R.Bauer on Thu, 05 June 2003 12:43
		Re: transparent background By: David Fanning on Thu, 05 June 2003 12:16

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