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print ROI coordinates in 2D image plots using the Marquee tool as input device

Posted October 11th, 2009 by harneit
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Here's a snippet to print the coordinates of a region of interest in a 2D image plot that was selected by the Marquee tool. Paste the code to the procedure window, compile, and use it on your image by drawing a Marquee box with the mouse, then right-click (Windows) or cmd-click (MacOS) to get the Marquee context menu, and choose "Print Image ROI". The snippet should work no matter which axes you use (top or bottom). You should have only one image on the plot, but this behavior can be changed easily, see comments in the code.

Menu "GraphMarquee"
	"Print Image ROI"
End
 
Function PrintImageROI()
// 1. get the marquee in point units (axis units directly accessible only for 1D graphs!)
// sanity test: let there be exactly one image
	String TopGraphImages = ImageNameList("",";")
	if( ItemsInList(TopGraphImages) != 1 )
		Print "There is either no image or more than one on the graph"
		return -1
	endif
	GetMarquee
// sanity test: was there a marquee at all?
	if (V_flag == 0)
		Print "There is no marquee"
		return -1
	endif
	Variable mpL = V_left, mpR = V_right, mpT = V_top, mpB = V_bottom
//	print "marquee in points (left, top, right, bottom) =", mpL, mpT, mpR, mpB
 
// 2. get the plot area in point units
	GetWindow kwTopWin, psize
	Variable ppL = V_left, ppR = V_right, ppT = V_top, ppB = V_bottom
//	print "plot area in points (left, top, right, bottom) =", ppL, ppT, ppR, ppB
 
// 3. get the axis limits
// get limits of axes that image is displayed against
	String theImage = StringFromList(0, TopGraphImages)
	String XAxis = StringByKey( "XAXIS", ImageInfo("", theImage, 0) )
	String YAxis = StringByKey( "YAXIS", ImageInfo("", theImage, 0) )
	String XAxisLimits = StringFromList(2, StringByKey( "SETAXISCMD", axisinfo("", XAxis) ), " " )
	String YAxisLimits = StringFromList(2, StringByKey( "SETAXISCMD", axisinfo("", YAxis) ), " " )
// order left/right correctly, remember whether a swap occurred
	Variable axMin = str2num( StringFromList(0, XAxisLimits, ",") ), axMax = str2num( StringFromList(1, XAxisLimits, ",") )
	Variable paL = min(axMin, axMax), paR = max(axMin, axMax), xSwap = (paL != axMin)
// order top/bottom correctly, remember whether a swap occurred
	axMin = str2num( StringFromList(0, YAxisLimits, ",") ); axMax = str2num( StringFromList(1, YAxisLimits, ",") )
	Variable paT = max(axMin, axMax), paB = min(axMin, axMax), ySwap = (paB != axMin)
//	print "plot area in axis units (left, top, right, bottom) =", paL, paT, paR, paB; print xSwap, ySwap
 
// 4. express the marquee coordinates in axis units
	Variable maL = paL + (mpL - ppL) * (paR - paL)/(ppR - ppL), maR = paL + (mpR - ppL) * (paR - paL)/(ppR - ppL), swap
	if( xSwap )
		swap = maL; maL = maR; maR = swap
	endif
	Variable maT = paT + (mpT - ppT) * (paB - paT)/(ppB - ppT), maB = paT + (mpB - ppT) * (paB - paT)/(ppB - ppT)
	if( ySwap )
		swap = maT; maT = maB; maB = swap
	endif
	print "marquee in axis units (left, top, right, bottom) =", maL, maT, maR, maB
End

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