Get coordinated of user drawn rectangle in image

//Only one rentangle considered... you may modify this code to fit your specific need
function  GetRoiCoord()
    string sw=winname(0,1)
    string simg=stringfromlist(0,imagenamelist("",";"))
    ImageGenerateROIMask $simg
    wave w=M_ROIMask
    variable l,t,r,b
    variable nx=dimsize(w,0)
    variable ny=dimsize(w,1)
    variable x0=dimoffset(w,0)
    variable dx=dimdelta(w,0)
    variable y0=dimoffset(w,1)
    variable dy=dimdelta(w,1)
    variable i,j,flag=0
    
    //this algorithm seems not so good,but works...
    for(i=0;i<nx;i+=1)
        for(j=0;j<ny;j+=1)
            if(w[i][j]==1)
                l=x0+dx*i
                t=y0+dy*j
                flag=1
                break
            endif
        endfor
        if(flag==1)
            break
        endif
    endfor
    flag=0
    for(i=nx-1;i>=0;i-=1)
        for(j=ny-1;j>=0;j-=1)
            if(w[i][j]==1)
                r=x0+dx*i
                b=y0+dy*j
                flag=1
                break
            endif
        endfor
        if(flag==1)
            break
        endif
    endfor
    print l,t,r,b  //left,top,right,bottom
end

// structure to collect marquee coordinates
Structure MarqueeCoordinates
    variable ispresent
    variable left
    variable right
    variable top
    variable bottom
EndStructure
 
// fill the structure
Function GetMCCoordinates(mc)
    Struct MarqueeCoordinates &mc
    
    GetMarquee/W=imgT_display/Z left,top
    mc.ispresent = v_flag
    mc.left = v_left
    mc.right = v_right
    mc.top = v_top
    mc.bottom = v_bottom
 
    return 0
end
 
    if (iBckg.MRoI != 1)
        // get marquee from image graph 
        STRUCT MarqueeCoordinates mc
        GetMCCoordinates(mc)
        if (!mc.ispresent)
            DoAlert/T="Show I Slice" 0, "No Marquee region is present. Set one and try again."
            return -1
        endif
    endif

Function MC_EndROI()
 
    SVAR MC_captureFrameImage  //Name of graph displaying the image of interest.
 
    Variable aCount, bCount           //Arbitrary counter variables
 
        //End user selection of ROI
    setdrawenv/W=$MC_captureFrameImage gstop
    hidetools/W=$MC_captureFrameImage
    drawaction/W=$MC_captureFrameImage/L=progfront getgroup=MC_ROISelection, extractoutline
 
        //Create pointers to W_PolyX and W_PolyY containing the polygon points of the user selected ROI.
        //Important assumption: the ROI is rectangular
    Wave W_PolyX
    Wave W_PolyY
    
        //Add a NaN to end of W_PolyX and W_PolyY to simplify later for-loop
    Redimension/N=(DimSize(W_PolyX,0)+1) W_PolyX
    Redimension/N=(DimSize(W_PolyY,0)+1) W_PolyY    
    W_PolyX[DimSize(W_PolyX,0)-1]=NaN
    W_PolyY[DimSize(W_PolyY,0)-1]=NaN
    
    Variable buffer, bufferSize, bufferPixel
        //Buffer wave for storing coordinates upper-left and lower-right corner of rectangle    
    Make/O/N=(2,2) bufferRectEdges
    
    bCount=0
    
    for(aCount=0;aCount<DimSize(W_PolyX,0);aCount+=1)
        
                //NaN separates polygons from each other
        if(numtype(W_PolyX[aCount])==2)
                //Initialite bufferRectEdges
            bufferRectEdges=0
            
                        //Upper-left corner x-coordinate
            bufferRectEdges[0][0]=W_PolyX[aCount-5]
                        //Upper-left corner y-coordinate
            bufferRectEdges[0][1]=W_PolyY[aCount-5]
                        //Lower-right corner x-coordinate
            bufferRectEdges[1][0]=W_PolyX[aCount-3]
                        //Lower-right corner y-coordinate
            bufferRectEdges[1][1]=W_PolyY[aCount-3] 
                  endif
 
    endfor
 
Variable top, left, width, height
 
top=min(bufferRectEdges[0][0],bufferRectEdges[0][1])
left=min(bufferRectEdges[0][1],bufferRectEdges[1][1])
width=abs(bufferRectEdges[0][0]-bufferRectEdges[1][0])
height=abs(bufferRectEdges[0][1]-bufferRectEdges[1][1])
 
End