setMinAndMax() fails on currently selected channel of a CompositeImage

Posted by Michael Ellis on May 21, 2010; 5:07pm
URL: http://imagej.273.s1.nabble.com/setMinAndMax-fails-on-currently-selected-channel-of-a-CompositeImage-tp3688229.html

I'm trying to write a plugin that will let me interactively manipulate  
a CompositeImage.
I find setMinAndMax() fails to work on the image processor returned by  
getProcessor(channelIndex)
for the currently selected channel of the CompositeImage.

The plugin below is a minimal piece of code that illustrates my problem.
  It creates an 8 bit 256x256 3 channel CompositeImage filling each  
channel with a ramp.
  By default the LUTS for each channel are:
    channel 1 = red
    channel 2 = green
    channel 3 = blue

I set the min and max values using setMinAndMax(175,200) for each  
channel.
I repeat this three times, selecting channel 1, then 2, then 3. In  
each case the
setMinAndMax(175,200) appears to fail for the currently selected  
channel.

My goal is to create a plugin where I can interactively adjust the  
enabled,
min and max values for every plane in a composite image.

Using setPosition() to select a channel other than the one I want to  
adjust
seems to work around the problem (try setting workAround to true) but  
this
seem inelegant and probably indicative that I am doing something wrong!

   Help!

/
*------------------------------------------------------------------------------------------------------------*/
import ij.CompositeImage;
import ij.IJ;
import ij.ImagePlus;
import ij.plugin.PlugIn;
import ij.process.ImageProcessor;

public class My_Plugin implements PlugIn {

        public My_Plugin() {
        }

        public void run(String arg) {
                for (int channelSelect = 1; channelSelect <= 3; ++channelSelect) {
                        ImagePlus imp = IJ.createImage("Chan select=" + channelSelect, "8-
bit Ramp", 256, 256, 3);
                        CompositeImage ci = new CompositeImage(imp,  
CompositeImage.COMPOSITE);
                        ci.show();

                        ci.setPosition(channelSelect);

                        for (int channelIndex = 1; channelIndex <= 3; ++channelIndex) {
                                boolean workAround = false;
                                if (workAround) {
                                        // Select any channel other than the one we are changing.
                                        ci.setPosition(channelIndex < 3 ? channelIndex + 1 : 1);
                                }
                                final int min = 175, max = 200;
                                ImageProcessor cip = ci.getProcessor(channelIndex);
                                cip.setMinAndMax(min, max);
                                ci.updateAndDraw();
                        }
                }
        }
}