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Home/ Questions/Q 6015127
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Editorial Team
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Editorial Team
Asked: May 23, 20262026-05-23T02:47:28+00:00 2026-05-23T02:47:28+00:00

I’ve an app that distorts a circle on a bitmap with a fisheye distortion.

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I’ve an app that distorts a circle on a bitmap with a fisheye distortion. the circle seems to be rotated 180 deg as well as distorted. Any ideas? there’s no clue to me as to why in the filter class. thanks Matt.

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;

import com.tecmark.HorizontalSlider.OnProgressChangeListener;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuffXfermode;
import android.graphics.PorterDuff.Mode;
import android.graphics.Shader.TileMode;
import android.os.Environment;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class TouchView extends View{


    private File tempFile;
    private byte[] imageArray;
    private Bitmap bgr;
    private Bitmap bm;
    private Bitmap bgr2 = null;;
    private Paint pTouch;
    private int centreX = 1;
    private int centreY = 1;
    private int radius = 50;
    private int Progress;
    private static final String TAG = "*********TouchView";
    private Filters f = null;

    public TouchView(Context context) {
        super(context);
       // TouchView(context, null);
    }




    public TouchView(Context context, AttributeSet attr) {
        super(context,attr);




        tempFile = new File(Environment.getExternalStorageDirectory().
                getAbsolutePath() + "/"+"image.jpg");

        imageArray = new byte[(int)tempFile.length()];


     try{

            InputStream is = new FileInputStream(tempFile);
            BufferedInputStream bis = new BufferedInputStream(is);
            DataInputStream dis = new DataInputStream(bis);


            int i = 0;

            while (dis.available() > 0) {
            imageArray[i] = dis.readByte();
            i++;
            }

            dis.close();

       } catch (Exception e) {

               e.printStackTrace();
            }



        BitmapFactory.Options bfo = new BitmapFactory.Options();
        bfo.inSampleSize = 1;

        bm = BitmapFactory.decodeByteArray(imageArray, 0, imageArray.length, bfo);
        bgr = Bitmap.createBitmap(bm.getWidth(), bm.getHeight(), bm.getConfig());
        bgr = bm.copy(bm.getConfig(), true);
        bgr2 = Bitmap.createBitmap(bm.getWidth(), bm.getHeight(), bm.getConfig());



      f = new Filters();
      //bgr2 = f.barrel(bgr,0.00022F);

        pTouch = new Paint(Paint.ANTI_ALIAS_FLAG);         
        pTouch.setXfermode(new PorterDuffXfermode(Mode.SRC_OUT)); 
        pTouch.setColor(Color.TRANSPARENT);
        pTouch.setStyle(Paint.Style.STROKE);


    }// end of touchView constructor


    public void findCirclePixels(){ 



    /*  for (int i=centreX-50; i < centreX+50; ++i) {
            for (int y=centreY-50; y <centreY+50 ; ++y) {

    if( Math.sqrt( Math.pow(i - centreX, 2) + ( Math.pow(y - centreY, 2) ) ) <= radius ){

                    bgr.setPixel(i,y,Color.rgb(Progress+50,Progress,Progress+100));
                }
            }
        }*/
        float prog = (float)Progress/2000000;
        bgr2 = f.barrel(bgr,prog);

        }// end of changePixel()




    @Override
    public boolean onTouchEvent(MotionEvent ev) {

        switch (ev.getAction()) {

            case MotionEvent.ACTION_DOWN: {

                centreX = (int) ev.getX();
                centreY = (int) ev.getY();
                findCirclePixels();
                invalidate();

                break;
            }

            case MotionEvent.ACTION_MOVE: {

                    centreX = (int) ev.getX();
                    centreY = (int) ev.getY();
                    findCirclePixels();
                    invalidate();
                    break;

            }           

            case MotionEvent.ACTION_UP: 

                break;

        }
        return true;
    }//end of onTouchEvent





    public void initSlider(final HorizontalSlider slider)
    {
        Log.e(TAG, "******setting up slider*********** ");
        slider.setOnProgressChangeListener(changeListener);
    }



    private OnProgressChangeListener changeListener = new OnProgressChangeListener() {


        @Override
        public void onProgressChanged(View v, int progress) {
            // TODO Auto-generated method stub

            setProgress(progress);
            Log.e(TAG, "***********progress = "+Progress);

        }
    };





    @Override
    public void onDraw(Canvas canvas){
        super.onDraw(canvas);


        canvas.drawBitmap(bgr2, 0, 0, null);
        canvas.drawCircle(centreX, centreY, radius,pTouch);



    }//end of onDraw




    protected void setProgress(int progress2) {
        this.Progress = progress2;
        findCirclePixels();
        invalidate();

    }


}

.

import android.graphics.Bitmap;
import android.util.Log;

class Filters{
    float xscale;
    float yscale;
    float xshift;
    float yshift;
    int [] s;
    private String TAG = "Filters";
    public Filters(){

        Log.e(TAG, "***********inside constructor");
    }

    public Bitmap barrel (Bitmap input, float k){
        Log.e(TAG, "***********inside barrel method ");
        float centerX=input.getWidth()/2; //center of distortion
        float centerY=input.getHeight()/2;

        int width = input.getWidth(); //image bounds
        int height = input.getHeight();

        Bitmap dst = Bitmap.createBitmap(width, height,input.getConfig() ); //output pic
        Log.e(TAG, "***********dst bitmap created ");
          xshift = calc_shift(0,centerX-1,centerX,k);
          float newcenterX = width-centerX;
          float xshift_2 = calc_shift(0,newcenterX-1,newcenterX,k);

          yshift = calc_shift(0,centerY-1,centerY,k);
          float newcenterY = height-centerY;
          float yshift_2 = calc_shift(0,newcenterY-1,newcenterY,k);

          xscale = (width-xshift-xshift_2)/width;
          yscale = (height-yshift-yshift_2)/height;
          Log.e(TAG, "***********about to loop through bm");
          /*for(int j=0;j<dst.getHeight();j++){
              for(int i=0;i<dst.getWidth();i++){
                float x = getRadialX((float)i,(float)j,centerX,centerY,k);
                float y = getRadialY((float)i,(float)j,centerX,centerY,k);
                sampleImage(input,x,y);
                int color = ((s[1]&0x0ff)<<16)|((s[2]&0x0ff)<<8)|(s[3]&0x0ff);
    //            System.out.print(i+" "+j+" \\");

                dst.setPixel(i, j, color);

              }
            }*/

          int origPixel;

          for(int j=0;j<dst.getHeight();j++){
              for(int i=0;i<dst.getWidth();i++){
                 origPixel= input.getPixel(i,j);
                float x = getRadialX((float)i,(float)j,centerX,centerY,k);
                float y = getRadialY((float)i,(float)j,centerX,centerY,k);
                sampleImage(input,x,y);
                int color = ((s[1]&0x0ff)<<16)|((s[2]&0x0ff)<<8)|(s[3]&0x0ff);
    //            System.out.print(i+" "+j+" \\");

                if( Math.sqrt( Math.pow(i - centerX, 2) + ( Math.pow(j - centerY, 2) ) ) <= 85 ){
                dst.setPixel(i, j, color);
                }else{
                    dst.setPixel(i,j,origPixel);
                }
              }
            }
        return dst;
    }

    void sampleImage(Bitmap arr, float idx0, float idx1)
    {
        s = new int [4];
      if(idx0<0 || idx1<0 || idx0>(arr.getHeight()-1) || idx1>(arr.getWidth()-1)){
        s[0]=0;
        s[1]=0;
        s[2]=0;
        s[3]=0;
        return;
      }

      float idx0_fl=(float) Math.floor(idx0);
      float idx0_cl=(float) Math.ceil(idx0);
      float idx1_fl=(float) Math.floor(idx1);
      float idx1_cl=(float) Math.ceil(idx1);

      int [] s1 = getARGB(arr,(int)idx0_fl,(int)idx1_fl);
      int [] s2 = getARGB(arr,(int)idx0_fl,(int)idx1_cl);
      int [] s3 = getARGB(arr,(int)idx0_cl,(int)idx1_cl);
      int [] s4 = getARGB(arr,(int)idx0_cl,(int)idx1_fl);

      float x = idx0 - idx0_fl;
      float y = idx1 - idx1_fl;

      s[0]= (int) (s1[0]*(1-x)*(1-y) + s2[0]*(1-x)*y + s3[0]*x*y + s4[0]*x*(1-y));
      s[1]= (int) (s1[1]*(1-x)*(1-y) + s2[1]*(1-x)*y + s3[1]*x*y + s4[1]*x*(1-y));
      s[2]= (int) (s1[2]*(1-x)*(1-y) + s2[2]*(1-x)*y + s3[2]*x*y + s4[2]*x*(1-y));
      s[3]= (int) (s1[3]*(1-x)*(1-y) + s2[3]*(1-x)*y + s3[3]*x*y + s4[3]*x*(1-y));
    }

    int [] getARGB(Bitmap buf,int x, int y){
        int rgb = buf.getPixel(y, x); // Returns by default ARGB.
        int [] scalar = new int[4];
        scalar[0] = (rgb >>> 24) & 0xFF;
        scalar[1] = (rgb >>> 16) & 0xFF;
        scalar[2] = (rgb >>> 8) & 0xFF;
        scalar[3] = (rgb >>> 0) & 0xFF;
        return scalar;
    }

    float getRadialX(float x,float y,float cx,float cy,float k){
      x = (x*xscale+xshift);
      y = (y*yscale+yshift);
      float res = x+((x-cx)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy)));
      return res;
    }

    float getRadialY(float x,float y,float cx,float cy,float k){
      x = (x*xscale+xshift);
      y = (y*yscale+yshift);
      float res = y+((y-cy)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy)));
      return res;
    }

    float thresh = 1;

    float calc_shift(float x1,float x2,float cx,float k){
      float x3 = (float)(x1+(x2-x1)*0.5);
      float res1 = x1+((x1-cx)*k*((x1-cx)*(x1-cx)));
      float res3 = x3+((x3-cx)*k*((x3-cx)*(x3-cx)));

      if(res1>-thresh && res1 < thresh)
        return x1;
      if(res3<0){
        return calc_shift(x3,x2,cx,k);
      }
      else{
        return calc_shift(x1,x3,cx,k);
      }
    }
}
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  1. Editorial Team
    Editorial Team
    2026-05-23T02:47:28+00:00Added an answer on May 23, 2026 at 2:47 am

    Are you sure it isn’t being rotated 90° and mirrored? That could be caused by transposing your X and Y axes. For example, I see you are calling buf.getPixel(y, x) despite Bitmap’s getPixel taking x and y rather than y and x.

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