List all X coordinates by given a Y coordinate in a line profiles by DM scripting - dm-script

Question

For a line profile (curve), I want to reach that list all X coordinates that corresponding a Y coordinate by given this Y coordinate. And I could get the minimum and maximum values of these x coordinates. Here supposed I want to list all the X coordinates corresponding y=8, is this correct or any other better way? Thx
Number minx, maxx
Image front=:getfrontimage()
GetSize( front, xsize, ysize )
for (i=0; i<xsize; i++)
{
x= getpixel(front, i, 8)
minx=min(x)
maxx=max(x)
}

Answer 1

You script becomes wrong when you use the min and max, because you can not get a minimum/maximum of a single value (or rather, it is always that value). What you want to do is likely:
image spec := RealImage("Test",4,100)
spec = trunc(Random()*10)
number v = 8
ClearResults()
number nCh = spec.ImageGetDimensionSize(0)
for( number i=0; i<nCh; i++)
{
if( v == sum(spec[i,0]) )
Result("\n Value "+ v +" # " + i )
}
(The sum() is needed here a a trick to convert an image-expression to a single value.)
However, going pixel-by-pixel in script can be slow. Whenever possible, try to code with image-expressions, because they are much faster (for big images).
I therefore often utilize a trick: I threshold an image for the value I search for, and then iterate over that mask as long as it is not all-zero. The max(img,x,y) command will return the first maximum if there are multiple, so I get an ordered list.
image spec := RealImage("Test",4,100)
spec = trunc(Random()*10)
spec.ShowImage()
number v = 8
image mask = (spec==v)?1:0
ClearResults()
while( 0<sum(mask) )
{
number x,y
max(mask,x,y)
Result("\n Value " + v +" # " + x )
mask[x,0]=0
}
Edit: Answering the question of the comment below.
This is how one gets the ZLP maximum (position and value) from a line-profile in calibrated values.
Precursor: DM contains all data as simple arrays and values (real or integer). These are the real data and unrelated to any calibrations. You see these values if you toggle the "calibration" checkbox off in the Image Status palette:
These are the values all script commands etc. will use, i.e. positions are always indices (starting from 0) and values are the raw numeric values stored.
These images or spectra are calibrated by defining an origin and scale (and unit) for each dimensional axis as well as the intensity (=value). These triplets of values can be found in the image display info of data:
Only when the "Show calibrated values" checkbox is checked, is the data displayed in calibrated values. However, the real values remain unchanged. Just the scale/origin values are used to convert the numbers.
If you want to use a script to use calibrated values, then you have to perform the same conversions in you script yourself.
Here is the example:
image spectrum := GetFrontImage()
number xScale = spectrum.ImageGetDimensionScale(0) // 0 for X dimension
number xOrigin = spectrum.ImageGetDimensionOrigin(0)
string xUnit = spectrum.ImageGetDimensionUnitString(0)
number iScale = spectrum.ImageGetIntensityScale()
number iOrigin = spectrum.ImageGetIntensityOrigin()
string iUnit = spectrum.ImageGetIntensityUnitString()
string info = "\n"
info += "Image ["+spectrum.ImageGetLabel()+"]:"
info += "\n\t Dimension calibration: nCh * " + xScale + " + " + xOrigin + " [" + xUnit + "]"
info += "\n\t Intensity calibration: (value - " + iOrigin + ") * " + iScale +" [" + iUnit + "]"
Result(info)
// Find ZLP maximum (uncalibrated values)
number maxP_ch, dummy, maxV_raw
maxV_raw = max(spectrum,maxP_ch,dummy)
info = "\n"
info += "\n\t The maximum position is at channel index: " + maxP_ch
info += "\n\t The maximum Value at maximum position is: " + maxV_raw
Result(info)
number maxP_cal = xOrigin + xScale * maxP_ch
number maxV_cal = (maxV_raw - iOrigin) * iScale
info = "\n"
info += "\n\t The maximum position is at : " + maxP_cal
info += "\n\t The maximum Value is : " + maxV_cal
Result(info)
Note the different calibration formulas between dimensional calibration and intensity calibration!