Java(android): how to average rgb in specific area

Question

I've written the java for image processing working on android. I try to build the method to average color in specific area of image. I found some same warning that i really don't know how to solve it. For example, the warnings tell me that "The value of the local variable "red" is not used", so in the first i solved by declare the int red at the top, but it can't fix. The "red","green","blue","xImage","yImage" are all the same. In addition, the TextView show zero in every variable.

and if i put return red << 16 | green << 8 | blue; the warning is lost, but TextView is still show zero.

Here is the java code. help me please T^T.

import java.io.File;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

import android.os.Bundle;
import android.os.Environment;
import android.widget.ImageView;
import android.widget.TextView;

public class ProcessPic extends Activity {

int xImage,yImage,red,green,blue;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_process);


    String path = Environment.getExternalStorageDirectory()+ "/TestProcess/picture.jpg";
    File imgFile = new File(path);

    Bitmap myBitmapPic = BitmapFactory.decodeFile(imgFile.getAbsolutePath());                  
    ImageView myImage = (ImageView) findViewById(R.id.my_image);
    myImage.setImageBitmap(myBitmapPic);
    ProcessPic test = new ProcessPic();
    test.AverageColor(myBitmapPic, 0, 200, 0, 200);


    TextView tv1 = (TextView)findViewById(R.id.textView1);
    TextView tv2 = (TextView)findViewById(R.id.textView2);
    TextView tv3 = (TextView)findViewById(R.id.textView3);
    TextView tv4 = (TextView)findViewById(R.id.textView4);
    TextView tv5 = (TextView)findViewById(R.id.textView5);

    tv1.setText(Integer.toString(xImage));
    tv2.setText(Integer.toString(yImage));
    tv3.setText(Integer.toString(red));
    tv4.setText(Integer.toString(green));
    tv5.setText(Integer.toString(blue));

}

public void AverageColor (Bitmap myBitmap,int minw, int maxw,int minh, int maxh){

    int xImage = myBitmap.getWidth();
    int yImage = myBitmap.getHeight();

    int red = 0;
    int green = 0;
    int blue = 0;
    int count = 0;

    for (int i=minw;i<maxw;i++){
        for (int j=minh;j<maxh;j++){
            int pixel = myBitmap.getPixel(i,j);

            red += pixel >> 16 & 0xFF;
            green += pixel >> 8 & 0xFF;
            blue += pixel & 0xFF;

            count++;        

        }
    }
    red /= count;
    green /= count;
    blue /= count;
    //return red << 16 | green << 8 | blue;

}

}

Hsin-Hsiang Hsin-Hsiang · Accepted Answer · 2013-12-23T08:51:46

you declared int xImage,yImage,red,green,blue; but you didn't use them.

Therefore, you got the warning.

because you declared local variables(xImage,yImage,red,green,blue) again in the function of AverageColor. You can removed the "int" inside the function of AverageColor.

Java(android): how to average rgb in specific area

1 Answers