interconverting regions and lines

[Michael Glotzer]

Could anyone enlighten me on how to interconvert region selections and  
(segmented) lines in ImageJ? Both regions and lines are defined by a  
series of points, but some measurements and other operations require a  
line and others require a region. Are they interconvertible at some  
level?


Thanks for your help.
_MG

[Wayne Rasband]

On May 8, 2009, at 10:31 AM, Michael Glotzer wrote:

> Could anyone enlighten me on how to interconvert region selections  
> and (segmented) lines in ImageJ? Both regions and lines are defined  
> by a series of points, but some measurements and other operations  
> require a line and others require a region. Are they  
> interconvertible at some level?

Area selections (except for composite selections) and line selections  
are defined by a list of points. To convert from an area selection to  
a line selection, get the list of points and use it to create a line  
selection. To convert a line selection to an area selection, get the  
list of points and use it to create an area selection. Here is a  
macro that converts an area selection to line selection and a line  
selection to an area selection:

    type = selectionType;
    getSelectionCoordinates(xCoordinates, yCoordinates);
    if (type==0||type==2) {
       // convert rectangle or polygon to polyline
       makeSelection("polyline", xCoordinates, yCoordinates);
    } else if (type==1||type==3||type==4) {
       // convert ellipse, freehand or traced selection to freeline
       makeSelection("freeline", xCoordinates, yCoordinates);
    } else if (type==6) {
       //convert segmented line to polygon
       makeSelection("polygon", xCoordinates, yCoordinates);
    } else if (type==7) {
       // convert polyline to freehand outline
       makeSelection("freehand", xCoordinates, yCoordinates);
    } else
       print("Unsupported type: "+type

-wayne