dcraw overflowing 16 bits - RAW Shooting and Processing - CHDK Forum
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dcraw overflowing 16 bits

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Offline yardleydobon

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dcraw overflowing 16 bits
« on: 04 / May / 2010, 20:52:27 »
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Has anyone else noticed that using dcraw to decode 10 bbp CHDK raws with dcraw -D -4 causes pixels greater than 255 to overflow? With these options dcraw multiplies by 256 when it should multiply by 64 for 10 bit pixels. Using the -S 1023 options doesn't make a difference. This happens for me with the current version and the older packaged Debian version. I'm not talking about clipping to (2^16)-1; the upper bits are lost and pixels that should be bright go dark.

Can someone else confirm this please? I've already emailed Dave Coffin about this.

Edit: Solved!
The problem was that I was reading the dcraw output as little-endian, but netpbm is stored as big-endian. I was initially using rawconvert which outputs as little-endian, so when I compared the output of both decoders read as little-endian it appeared exactly like the dcraw output was overflowing.
« Last Edit: 04 / May / 2010, 22:03:28 by yardleydobon »
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