How to know the pixel size(width, length, height)

Dear All,

I have the data as attached (data.mat), anyone know how to see the pixel size (length, width, height) my data?

whos -file data.mat

  Name        Size                   Bytes  Class     Attributes

  data      128x128x128            8388608  single              

Answer 1

[DGM]

If this data came with an associated header file, then things like scaling info should be there.

Considering the stack from one of the prior questions, the header file point1_air_w1.h00 contains the following lines:

scaling factor (mm/pixel) [1] := 4.480

scaling factor (mm/pixel) [2] := 4.480

;# scaling factor (mm/pixel) [3] := 4.480

[mohd akmal masud]

Dear @DGM, the header file as attached.

[Walter Roberson]

That .hdr file contains

scaling factor (mm/pixel) [1] := 4
scaling factor (mm/pixel) [2] := 4
scaling factor (mm/pixel) [3] := 4

For a "one-off" you can just assume those values, but in general you should have your code parse them out from the file.

You should possibly be using niftiread and niftiinfo

Answer 2

[Walter Roberson]

You do not know those based on that data array. The only possible way to figure it out would be if somewhere inside the data array, there was an object whose physical size you knew.

I like to ask, "How big is an Imperial Star Destroyer" (Star Wars) ? It the original films, it is shown to be huge -- supposedly 1.6 kilometers long, with over 35000 people as staff / crew. You can get some idea by looking at how large other objects are as they go past it. But the real answer is something on the order of 1.5 meters for the model used in filming: the rest is due to perspective.

So unless you have external information or something of known size to compare to, you cannot tell whether what you are looking at is 1.5 millimeters or 1.5 meters or 1.5 kilometers...