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#91
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In article , Mike
Russell wrote: Mike Engles wrote: ... [re linear encoding of specialized pixel data values] Is the same true for imaging from spacecraft, interplanetary or otherwise or is gamma encoding done before transmission? Yes. Gama encoding compresses some data values, and there is no reason to do this to raw data from a spacecraft. Here's an article that may interest you, by Alvy Ray Smith, on the distinction of work and display color spaces. http://alvyray.com/Memos/MemosMicros...rAlphaQuestion Actually, Alvy has a number of mistakes in that paper. I'm still not sure if he understands gamma encoding... Chris |
#92
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In article , Mike
Russell wrote: Mike Engles wrote: ... [re linear encoding of specialized pixel data values] Is the same true for imaging from spacecraft, interplanetary or otherwise or is gamma encoding done before transmission? Yes. Gama encoding compresses some data values, and there is no reason to do this to raw data from a spacecraft. Here's an article that may interest you, by Alvy Ray Smith, on the distinction of work and display color spaces. http://alvyray.com/Memos/MemosMicros...rAlphaQuestion Actually, Alvy has a number of mistakes in that paper. I'm still not sure if he understands gamma encoding... Chris |
#93
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In article , Mike
Russell wrote: OTOH, Adobe's weird 16 bit format makes it more difficult to interface to other graphics libraries, requiring additional passes to convert to and from 16 bit mode. That's why the external representation is 0..65535. Only the filter plugin APIs have to deal with the 0..32768 representation. There are flags for the file format, import, and export plugin APIs to use different maximum values (which Photoshop will then rescale to it's internal representation). Chris |
#94
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In article , Mike
Russell wrote: OTOH, Adobe's weird 16 bit format makes it more difficult to interface to other graphics libraries, requiring additional passes to convert to and from 16 bit mode. That's why the external representation is 0..65535. Only the filter plugin APIs have to deal with the 0..32768 representation. There are flags for the file format, import, and export plugin APIs to use different maximum values (which Photoshop will then rescale to it's internal representation). Chris |
#95
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In message ,
Chris Cox wrote: In article , wrote: In message , Chris Cox wrote: Without your original data to test, I can't even guess what went wrong. You don't need my original data. Any image in "16 bit greyscale" mode has all kinds of numbers between 0 and 32768 missing, Only if you started with an image that had numbers missing. The representation is 0..32768 -- all numbers are possible. and not possible no matter hown much you blur or interpolate. "16 bit greyscale" is about 13.5 bit greyscale. No, that is not even remotely correct. It is exactly what is happening here. I get 0, 1, 3, 4, 5, 8, etc. No 2, 6, 7, 11, etc, at all, no matter what is done to the data. That's with color management disabled. With it enabled, I had even less values. Clusters of 6 16-bit numbers all became the same "15bit+1" value when color management was enabled (except 3 values became 0, and 3 values became 32768). I could write this off to a corrupted executable, but it happens on two different installations of CS. -- John P Sheehy |
#96
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In message ,
Chris Cox wrote: In article , wrote: In message , Chris Cox wrote: Without your original data to test, I can't even guess what went wrong. You don't need my original data. Any image in "16 bit greyscale" mode has all kinds of numbers between 0 and 32768 missing, Only if you started with an image that had numbers missing. The representation is 0..32768 -- all numbers are possible. and not possible no matter hown much you blur or interpolate. "16 bit greyscale" is about 13.5 bit greyscale. No, that is not even remotely correct. It is exactly what is happening here. I get 0, 1, 3, 4, 5, 8, etc. No 2, 6, 7, 11, etc, at all, no matter what is done to the data. That's with color management disabled. With it enabled, I had even less values. Clusters of 6 16-bit numbers all became the same "15bit+1" value when color management was enabled (except 3 values became 0, and 3 values became 32768). I could write this off to a corrupted executable, but it happens on two different installations of CS. -- John P Sheehy |
#97
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On Mon, 22 Nov 2004 00:07:44 GMT, Chris Cox
wrote: This is still a problem. When 64 bit processors become the norm (and the @#!^&$ OS allows a fully 64 bit application), then that becomes less of a problem. Is a 64 bit optimised Photoshop likely to be faster, or just more able to do complex operations? Or do the programmers generally aim for a bit of both if you'll pardon the pun -- Hecate - The Real One veni, vidi, reliqui |
#98
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In article ,
wrote: In message , Chris Cox wrote: In article , wrote: In message , Chris Cox wrote: Without your original data to test, I can't even guess what went wrong. You don't need my original data. Any image in "16 bit greyscale" mode has all kinds of numbers between 0 and 32768 missing, Only if you started with an image that had numbers missing. The representation is 0..32768 -- all numbers are possible. and not possible no matter hown much you blur or interpolate. "16 bit greyscale" is about 13.5 bit greyscale. No, that is not even remotely correct. It is exactly what is happening here. I get 0, 1, 3, 4, 5, 8, etc. No 2, 6, 7, 11, etc, at all, no matter what is done to the data. And, again, without your original data - I can't guess what could have gone wrong. I do know that for anyone else doing a similar experiment (inside and outside Adobe), they get the full 32769 values. Chris |
#99
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In article ,
wrote: In message , Chris Cox wrote: In article , wrote: In message , Chris Cox wrote: Without your original data to test, I can't even guess what went wrong. You don't need my original data. Any image in "16 bit greyscale" mode has all kinds of numbers between 0 and 32768 missing, Only if you started with an image that had numbers missing. The representation is 0..32768 -- all numbers are possible. and not possible no matter hown much you blur or interpolate. "16 bit greyscale" is about 13.5 bit greyscale. No, that is not even remotely correct. It is exactly what is happening here. I get 0, 1, 3, 4, 5, 8, etc. No 2, 6, 7, 11, etc, at all, no matter what is done to the data. And, again, without your original data - I can't guess what could have gone wrong. I do know that for anyone else doing a similar experiment (inside and outside Adobe), they get the full 32769 values. Chris |
#100
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In article , Hecate
wrote: On Mon, 22 Nov 2004 00:07:44 GMT, Chris Cox wrote: This is still a problem. When 64 bit processors become the norm (and the @#!^&$ OS allows a fully 64 bit application), then that becomes less of a problem. Is a 64 bit optimised Photoshop likely to be faster, or just more able to do complex operations? Or do the programmers generally aim for a bit of both if you'll pardon the pun That depends a lot on the CPU in question, and the operation in question. Most likely there will be little performance difference, but a big difference in available RAM (addressibility). Chris |
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