| Re: converting Png files to Double [message #31684] |
Mon, 05 August 2002 15:05  |
thompson
Messages: 584
Registered: August 1991
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Senior Member |
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I was able to create a 16 bit PNG file in IDL, and then read it back in again,
with the following commands
IDL> a=dist(100)
% Compiled module: DIST.
IDL> a=32767.*a/max(a)
IDL> write_png,'test.png',uint(a)
% Loaded DLM: PNG.
IDL> b=read_png('test.png')
IDL> help,b
B UINT = Array[100, 100]
IDL> print,min(b),max(b)
0 32767
As far as I can tell, this is a valid PNG file--it displayed correctly in
Netscape.
William Thompson
"Rick Towler" <rtowler@u.washington.edu> writes:
> It would be helpful if you post a link to an example .png file.
> I am assuming you are working with a 16 bits per channel image? Photoshop
> isn't allowing me to write a 16 bit/channel .png so I can only use read_png
> with an 8 bit/channel image which returns a byte array.
> Or, are you combining two 8 bit channels to get your UINT value which you
> are trying to convert to double? If this is the case you need to convert at
> least one channel to UINT before multiplying.
> -Rick
> "ramji digumarthi" <ramji.digumarthi@lmco.com> wrote in message
> news:43689765.0208051003.c076e39@posting.google.com...
>> Hi folks,
>> I am currently working with BW PngFiles. I use READ_PNG command to
>> read the png file. Then I try to convert data into double precision
>> for some data analysis.
>> It is not working as I expected. The maximum value seem to be about 3
>> to 8?
>>
>> I see that READ_PNG is reading the file a UINT [Unsigned Integer: A
>> 16-bit unsigned integer ranging from 0 to 65535]. But when I convert
>> UINT to DOUBLE ,
>> I am getting only values in single digits???
>>
>> Can any one help on item?
>>
>> thank
>> Ramji Digumarthi
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