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09-12-2019, 10:42 AM   #1
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How to get numerical pixel values from PEF/DNG or TIFF files?

Is there a simple way to get the intrinsic numerical pixel values in an image?

In PhotoShop Elements (PSE), I can see the RGB pixel values as I move the cursor around, but they are in the 0-255 range, and have clearly been scaled by the program (i.e. if you apply, say, the histogram sliders, the values change).

For the K-1 with 14 bits, there should be values in the image file ranging from 0 to 16383 or there abouts.

Programs like MATLAB seem like they can do this, but is there anything simpler that will just show actual unscaled numerical pixel values? Certainly all image processing (and most, if not all, display) programs have these values internally, but I have not found a simple/easy way to get them revealed.

In astronomy, a standard for image files is FITS (flexible image transport system) and analysis programs based on FITS files display the actual pixel values as you scroll around in an image. It sure would be nice if there was something similar for our camera files. Seems to me like it would a trivial add-on to e.g. PSE, DCU5, DxO, etc.

Any ideas?

09-12-2019, 11:00 AM - 1 Like   #2
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QuoteOriginally posted by AstroDave Quote
How to get numerical pixel values from PEF/DNG or TIFF files?
RawDigger should be able to do this for you as might LibRaw or dcraw.


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09-12-2019, 11:13 AM   #3
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Yeah - I've got a bead on RawDigger

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09-12-2019, 11:15 AM   #4
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If you use the crop tool in eg faststone, and draw out a crop starting from the bottom left corner, then the size values = x and y values.

09-12-2019, 11:59 AM   #5
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QuoteOriginally posted by AstroDave Quote
Is there a simple way to get the intrinsic numerical pixel values in an image?

In PhotoShop Elements (PSE), I can see the RGB pixel values as I move the cursor around, but they are in the 0-255 range, and have clearly been scaled by the program (i.e. if you apply, say, the histogram sliders, the values change).

For the K-1 with 14 bits, there should be values in the image file ranging from 0 to 16383 or there abouts.

Programs like MATLAB seem like they can do this, but is there anything simpler that will just show actual unscaled numerical pixel values? Certainly all image processing (and most, if not all, display) programs have these values internally, but I have not found a simple/easy way to get them revealed.

In astronomy, a standard for image files is FITS (flexible image transport system) and analysis programs based on FITS files display the actual pixel values as you scroll around in an image. It sure would be nice if there was something similar for our camera files. Seems to me like it would a trivial add-on to e.g. PSE, DCU5, DxO, etc.

Any ideas?
One of the issues you are seeing is related to the fact that in most cases, the image you see is an RGB conversion of the actual raw fife and therefore limited to 28 values (256) in each channel since RGB is 8-bit. I think Steve has steered you in the right direction.
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