2004.01.23 04:48 "[Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB", by Pushkar Pradhan

2004.01.23 18:55 "Re: [Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB", by Frank Warmerdam

"sample" == "band" == "channel" == "component" ==?

Thanks Frank. Now I know I finally did understand it correctly. Am I also correct in thinking that the only proper way ignorant software (as in software that doesn't know about how the image came about or what it is intended to contain) can correctly interpret this 3-channel image as a grayscale image with 2 extra channels that have no specified application/meaning? If ignorant software were to have to render this image, the correct thing to do is to render the first channel as grayscale, and discard the others as far as rendering is concerned, is that right? I realize this may also be trivial questions, but this thread is very confusing.


I am by no means an authority on the TIFF specification. My interpretation of the file in question is that a sensible application should render the first band in greyscale and ignore the 2nd and 3rd since they are extra samples with no meaning attached. Without the ExtraSamples tag, I think an application should assume the file contains 3 greyscale bands which might be drawn in any number of ways. One way would be to draw 1 band, and give the user the ability to flip through to see the 2nd and 3rd. Another would be to just treat them as RGB (as many multispetral imaging packages will do with the first 3 bands of multispectral data).

A viewing application that only showed the first band as greyscale with no options to inspect the others would be acceptable and reasonable, but that viewer would have little utility in the rather small work of multispectral image processing (IMHO).

Best regards,

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