Max Sample value higher than 255

Started by neebah, May 10, 2016, 08:14:57 AM

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neebah

May 10, 2016, 08:14:57 AM
I scanned a file to Tiff at 48 bit and its shows Bits per Sample to be 16 16 16 (which makes sense), but the Max Sample Value is 255.  Shouldn't it be 65535?  I'm just afraid my scanner isn't really 48 bit

Phil Harvey

#1
May 10, 2016, 11:13:28 AM
Sounds suspicious.  Yes, one would think that it should be 64k for a full 16-bit-per-pixel image.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

neebah

#2
May 10, 2016, 11:33:08 AM
I checked the bits for the image strip and its storing the right amount of bits. 

And they aren't just duplicates or anything.   Its just that the maximumsample is not storing at 65535

neebah

#3
May 10, 2016, 11:37:52 AM
Other than number of bytes in the tiff strip and lack of obvious byte duplication is there anyway to insure that the scanner really scanned at 48 bit.  I'm not really skeptical of the scanner.  Lord knows it could have just stored the wrong piece of information in the maxsample

Phil Harvey

#4
May 10, 2016, 11:59:58 AM
You can take a look at the image data and see if the top half of all words is 0.  You should also be able to see the raw pixel values if you load into photoshop or some other image viewer.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

neebah

#5
May 10, 2016, 12:14:31 PM
Here is a hex dump of the image data.  Looks like I'm okay.  Granted this was a scan top of the scanner lid. 

6c f9 43 fb 84 fe 37 fa  87 fc 5e fb f3 fa 82 fc
77 fb 6d fd 69 fc c0 fb  a2 fc dd fb 0f fa 87 fc
62 fc 88 fb 72 fe 0c fc  31 fa f9 fd f9 fc cb fb
30 fc 03 fd 91 fc dd fc  60 fe 26 fa 69 fd b9 fe
24 fc 5c fd 2c fe 0c fa  e6 fc e3 fc fb fb 04 fe
e0 fc b5 fd 9c fe fd fc  bd fc e5 fc fe fc 0b fb
39 fd 97 fd f6 fc 62 fd  57 fd 6b fc bf fd d9 fc
35 fb 08 fd 76 fd 2a fc  1b fc 15 fc 82 fc f1 fc
                [snip 922 lines]               
48 fa f9 fa aa fb 8b fa  bb fa db fb fb f9 d0 fb
10 fd 8d f8 76 fb 1f fd  15 f9 f5 f9 24 fb 38 f9
67 f9 35 fb db f9 7f f9  2e fb 1f f9 5f f8 a3 fb
9f f7 06 fa 52 fa 08 f9  1d fa 97 fb 20 f9 92 fa
21 fb 88 f9 52 f9 57 fc  09 f8 12 f8 50 fb 38 f8
e5 f8 27 f9 3e f9 32 f9  a8 f8 cf f8 8f f8 bc f9
ea f7 4f f9 cb fa 64 f8  07 fa 7c fa a3 f9 bd f8
06 fc d6 f7 84 f8 dc f8

Phil Harvey

#6
May 10, 2016, 02:17:59 PM
Yup.  Looks OK as long as the image is uncompressed.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

neebah

#7
May 10, 2016, 02:47:41 PM
It most certainly is uncompressed   ;)
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