Question about Pixel Intensity Measurements


I have been taking intensity measurements in FIJI using “Analyze > Tools > Save XY Coordinates”, however, sometimes I get integers for the intensity values column and sometimes I get floating variables. Interestingly, saving values using this method for the entire image, using the rectangle tool, oval tool, or a horizontal/vertical line gives me integers, while using a diagonal line or the segmented tool gives me values with decimals.

So my question is, why are they different? If the command is saving the intensity values for each pixel in an XY plane, shouldn’t they be either all integers or all floating variables regardless of what contour I used?


P.S. for using a segmented line, I have been using the “straighten” command to define the ROI before getting the XY intensity values.

Hello Terry -

It appears to me that the Edit > Selection > Straighten...
command calculates interpolated pixel values, and does so in
floating point. Then Save XY Coordinates... writes those
floating-point values to the output file.

If I create an 8-bit image, File > New > Image..., Type: 8-bit,
select a rectangular region, and run Save XY Coordinates...,
I indeed get integer values. If instead I create a Type: 32-bit
(that is, floating-point) image, Save XY Coordinates... gives
me floating-point values.

If I create an 8-bit image, select a straight line segment, and run
Edit > Selection > Straighten..., Fiji creates a second,
32-bit image, whose width is the length of my line, and whose height
is 20 pixels. If I then run Save XY Coordinates..., it is run on
that second image, and writes floating-point values to the output file.

Thanks, mm