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Re: Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG [message #93667 is a reply to message #93615]

Mon, 26 September 2016 17:33

andrewcool777
Messages: 27
Registered: November 2012

Junior Member

On Tuesday, 6 September 2016 21:18:06 UTC+9:30, Markus Schmassmann wrote:
> On 09/05/2016 05:11 AM, andrewcool777@gmail.com wrote:
>> The PNG image format is a wonderous thing. Lossless, but with user
>> selectable variable compression, 8 or 16bit image data, and most
>> importantly, the ability to have user-defined metadata!
>>
>> Yet for some reason, in their infinite wisdom, RSI never provided the
>> functionality to read or write the metadata when they wrote the
>> routines! :-(
>>
>> I run a number of airglow cameras, provided by the great guys at Keo
>> Scientific, and the images are saved as PNG files, with a basic set
>> of metadata. Now I've been able to write IDL code to extract that
>> metadata, and write PNG files with (extended, modified) metadata, as
>> reported previously, but it's quite (read _very_) slow, and would
>> definitely be better off done within the IDL Read_PNG and Write_PNG
>> routines!
>>
>> However, as I'm the only IDL user on the planet to request this
>> feature, I'm told by Harris Support that it won't happen unless more
>> users put their hands up and say "Me too, please!"
>>
>> So here's my plea to you. If you think it might be a Good Thing to
>> have IDL's own PNG routines handle the reading and writing of user
>> supplied metadata, please submit a Feature Request to
>> support@harris.com to this effect.
>>
>> Many Hosannas will be said in your name for doing so...
> Hi Andrew
>
> Having experienced tediously slow read in of FITS-files/headers and
> having spent some time optimizing these read-in routines i wonder,
> whether you could increase your PNG read-in routine speed by up to 2
> order of magnitudes by providing the structure templates for the
> metadata instead of using many create_struct() calls on runtime. But
> obviously i can't tell without seeing the code.
>
> Markus

Hi Markus,

PNG Metadata is nothing like FITS. The metadata has to be read in chunks, byte by byte, and the image data has to be compressed/decompressed byte by byte on the fly, which is the big consumer of time. There are no create_struct() calls involved.

Andrew

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[Message index]

		Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG By: andrewcool777 on Sun, 04 September 2016 20:11
		Re: Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG By: markb77 on Tue, 06 September 2016 04:26
		Re: Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG By: Dick Jackson on Tue, 06 September 2016 08:31
		Re: Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG By: andrewcool777 on Mon, 26 September 2016 17:25
		Re: Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG By: Markus Schmassmann on Tue, 06 September 2016 04:48
		Re: Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG By: andrewcool777 on Mon, 26 September 2016 17:33
		Re: Crowd support wanted for adding metadata to READ_PNG and WRITE_PNG By: penteado on Wed, 07 December 2016 16:54

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