// Image annotation macro originally wrote by Nick McDougall
// 2018/08/30 Zhou Xu modified 
// @ Monash Centre for Electron Microscopy
// modified to support grey scale, 24bit RGB image formats
// font color auto-adjusted for the background color at the middle point of the line

fontSize = 24;
	run("Measure");
	label = getResult("Length", nResults-1);
	   getVoxelSize(width, height, depth, unit);
	   if (label>10)
	   label = d2s(label,1);
	   else
	      label = d2s(label,2);
	   label = label + " " + unit;
	   setJustification("left");
       setFont("SansSerif", fontSize);
       getLine(x1, y1, x2, y2, lineWidth);
       v = getPixel((x1+x2)*0.5,(y1+y2)*0.5);

if (bitDepth==24) {
            red = (v>>16)&0xff;  // extract red byte (bits 23-17)
            green = (v>>8)&0xff; // extract green byte (bits 15-8)
            blue = v&0xff;       // extract blue byte (bits 7-0)
            Luminance = 0.2126 * red + 0.7152 * green + 0.0722 * blue;
} 
else {
Luminance = v;
}

if (Luminance <90) {
	setColor("white");
          }
	   else {
	   	setColor("black");
}
	   run("Draw", "slice");
       
	   if (label>10)
	      drawString(label, (x1+x2)*0.5+fontSize*0.5, (y1+y2)*0.5+fontSize*0.5);
	   else
	      drawString(label, (x1+x2)*0.5+fontSize*0.5, (y1+y2)*0.5+fontSize*0.5);
}