This Rhinoscript takes any image reads the luminance value of the image at a user-specified 2d increment and uses the results as a scalar multiplier against a user-specified value for a selected set of objects.

Rhino Script

Option Explicit
'Script written by <David Mans>
'adapted from work by Che Wei Wang
'www.cwwang.com
'Script copyrighted by <NeoArchaic Studio>
'Script version Tuesday, March 18, 2008 7:40:18 AM

Call Main()
Sub Main()
	Dim arrObjects: arrObjects = Rhino.GetObjects("Select Objects",, True)
	If isNull(arrObjects) Then Exit Sub
	
	Dim arrItems, arrValues, arrResults
	arrItems = array("columns", "rows", "maximum_scale_height")
	arrValues = array(10, 10, 2)
	arrResults = Rhino.PropertyListBox(arrItems, arrValues,, "Image Parameters")
	
	Dim arrImg
	
	arrImg = arrImageSample(arrResults(0), arrResults(1))
	' image outputs (0)red(1)green(2)blue(3)alpha(4)hue(5)saturation(6)luminance
	
	
	Call Rhino.EnableRedraw(False)
	Call scaleByImage(arrObjects, arrImg(6), CDbl(arrResults(2)))
	Call Rhino.DeleteObjects(arrObjects)
	Call Rhino.EnableRedraw(True)
	
End Sub
Function scaleByImage(arrObjects, arrValues, dblScale)
	scaleByImage = Null
	Dim i, j, x, y, bBox
	
	bBox = Rhino.BoundingBox(arrObjects)
	x = Rhino.Distance(bBox(0), bBox(1))
	y = Rhino.Distance(bBox(0), bBox(3))
	
	Dim arrOutput(),tOutput()
	ReDim arrOutput(uBound(arrValues))
	
	For i = 0 To uBound(arrValues) - 1 Step 1
		ReDim tOutput(uBound(arrValues(i)))
		For j = 0 To uBound(arrValues(i)) - 1 Step 1
			tOutput(j) = Rhino.ScaleObjects(Rhino.CopyObjects(arrObjects, array(0, 0, 0), array(x * i, y * j, 0)), array(0, 0, 0), array(1, 1, 1 + dblScale * arrValues(i)(j)))
		Next
		arrOutput(j) = tOutput
	Next
	
	scaleByImage = arrOutput
End Function
Function arrImageSample(cols, rows)
	arrImageSample = Null
	'Instantiate the RhPicture Object
	Dim RhPicture : Set RhPicture = Rhino.GetPlugInObject("RhPicture")
	If IsNull(RhPicture) Then Exit Function
	
	'Load an arbitrary image
	If Not RhPicture.LoadImage() Then 
		Call Rhino.Print("Image not loaded")
		Exit Function
	End If
		
	'Get the width and height
	Dim w : w = RhPicture.Width()
	Dim h : h = RhPicture.Height()

	If IsNull(w) Or IsNull(h) Then
		Call Rhino.Print("No valid image data")
		Exit Function
	End If
	
	Dim x, y, i,j
	Dim r, g, b, a, hu, s, u
	ReDim r(rows), g(rows), b(rows), a(rows), hu(rows), s(rows), u(rows)
	Dim rValSet, gValSet, bValSet, aValSet, hValSet, sValSet, uValSet
	ReDim rValSet(cols), gValSet(cols), bValSet(cols), aValSet(cols), hValSet(cols), sValSet(cols), uValSet(cols)
	
	'Sample Image returning all values between zero and one
	For i = 0 To cols Step 1
		For j = 0 To rows Step 1
			x = int(w / cols) * i
			y = int(h / rows) * j
			
			If x > w Then
				x = w
			End If
			
			If y > h Then
				y = h
			End If
			
			r(j) = RhPicture.Red(x, y) / 255
			g(j) = RhPicture.Green(x, y) / 255
			b(j) = RhPicture.Blue(x, y) / 255
			a(j) = RhPicture.Alpha(x, y) / 255
			hu(j) = RhPicture.Hue(x, y) / 360
			s(j) = RhPicture.Saturation(x, y)
			u(j) = RhPicture.Luminance(x, y)
			
		Next
		rValSet(i) = r
		gValSet(i) = g
		bValSet(i) = b
		aValSet(i) = a
		hValSet(i) = hu
		sValSet(i) = s
		uValSet(i) = u
	Next
	Set RhPicture = Nothing
	' image outputs (0)red(1)green(2)blue(3)alpha(4)hue(5)saturation(6)luminance
	arrImageSample = array(rValSet, gValSet, bValSet, aValSet, hValSet, sValSet, uValSet)
End Function