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2012/05/14 (2012/05 Archive)

.knob file format

Can anyone write a Mac Finder extension for JKnobMan's .knob thumbnailing...? Unfortunately, I'm not so familiar with mac development. Anyway the necessary information is here.

There are 2 types of .knob format

Old version : "PNG" type

The first 2bytes are "0x89, 0x50". The file extension is ".knob" but the file contents is the thumbnail PNG image itself (The knob information is embedded in the PNG's text chunk). This format is obsoleted because some browser (IE) forcibly process as Image-file.

Current version : "KM" type

The first 2bytes are "0x4b, 0x4d" (KM).

Signature2bytes0x4b, 0x4d //"KM"
Offset4bytesOffset to KnobData
PNG Imagevairable lengththumbnail PNG image (lacking the first 6bytes)
KnobDatavariable lengthInformation for knob

Because PNG's first 8 bytes are fixed header, knob-file can be easily processed as a thumbnail png image with overwriting the first 6byte to "0x89,0x50,0x4e,0x47,0x0d,0x0a".

Posted by g200kg : 2012/05/14 01:19:22