Fixed size Rectangular ROI tool for IJ1

SubfieldTool.ijm

/* Subfield Tool.ijm
 * IJ BAR: https://github.com/tferr/Scripts
 *
 * Creates a square ROI sized from on the length of a straight line
 */

var sizeRatio = 1/3;

macro "SubField Tool - C037 L0ff0 R3399" {
    getCursorLoc(x, y, z, flags);
    xstart = x; ystart = y;
    x2 = x; y2 = y;
    while (flags&16!=0) {
        getCursorLoc(x, y, z, flags);
        if (x!=x2 || y!=y2)
            makeLine(xstart, ystart, x, y);
    }
    dx = (x2 - x);
    dy = (y2 - y);
    width = sizeRatio * sqrt(dx * dx + dy * dy);
    xMid = (x2 + x) / 2;
    yMid = (y2 + y) / 2;
    makeRectangle(xMid, yMid, width, width);
    setTool(0);
}

macro "SubField Tool Options" {
    sizeRatio = getNumber("ROI width (fraction of line length)", sizeRatio);
}