Question

I am developing an application in which there is a module for Image warping.I referred several sites but could not get any solution that could solve my problem.

Any tutorials/links or suggestions for face warping would be helpful.

Answer 1

This is from the samples shipped with Android SDK. From your question it’s not clear if you want to know the Android API or the very warping algorithm

public class BitmapMesh extends GraphicsActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
    }

    private static class SampleView extends View {
        private static final int WIDTH = 20;
        private static final int HEIGHT = 20;
        private static final int COUNT = (WIDTH + 1) * (HEIGHT + 1);

        private final Bitmap mBitmap;
        private final float[] mVerts = new float[COUNT*2];
        private final float[] mOrig = new float[COUNT*2];

        private final Matrix mMatrix = new Matrix();
        private final Matrix mInverse = new Matrix();

        private static void setXY(float[] array, int index, float x, float y) {
            array[index*2 + 0] = x;
            array[index*2 + 1] = y;
        }

        public SampleView(Context context) {
            super(context);
            setFocusable(true);

            mBitmap = BitmapFactory.decodeResource(getResources(),
                                                     R.drawable.beach);

            float w = mBitmap.getWidth();
            float h = mBitmap.getHeight();
            // construct our mesh
            int index = 0;
            for (int y = 0; y <= HEIGHT; y++) {
                float fy = h * y / HEIGHT;
                for (int x = 0; x <= WIDTH; x++) {
                    float fx = w * x / WIDTH;                    
                    setXY(mVerts, index, fx, fy);
                    setXY(mOrig, index, fx, fy);
                    index += 1;
                }
            }

            mMatrix.setTranslate(10, 10);
            mMatrix.invert(mInverse);
        }

        @Override protected void onDraw(Canvas canvas) {
            canvas.drawColor(0xFFCCCCCC);

            canvas.concat(mMatrix);
            canvas.drawBitmapMesh(mBitmap, WIDTH, HEIGHT, mVerts, 0,
                                  null, 0, null);
        }

        private void warp(float cx, float cy) {
            final float K = 10000;
            float[] src = mOrig;
            float[] dst = mVerts;
            for (int i = 0; i < COUNT*2; i += 2) {
                float x = src[i+0];
                float y = src[i+1];
                float dx = cx - x;
                float dy = cy - y;
                float dd = dx*dx + dy*dy;
                float d = FloatMath.sqrt(dd);
                float pull = K / (dd + 0.000001f);

                pull /= (d + 0.000001f);
             //   android.util.Log.d("skia", "index " + i + " dist=" + d + " pull=" + pull);

                if (pull >= 1) {
                    dst[i+0] = cx;
                    dst[i+1] = cy;
                } else {
                    dst[i+0] = x + dx * pull;
                    dst[i+1] = y + dy * pull;
                }
            }
        }

        private int mLastWarpX = -9999; // don't match a touch coordinate
        private int mLastWarpY;

        @Override public boolean onTouchEvent(MotionEvent event) {
            float[] pt = { event.getX(), event.getY() };
            mInverse.mapPoints(pt);

            int x = (int)pt[0];
            int y = (int)pt[1];
            if (mLastWarpX != x || mLastWarpY != y) {
                mLastWarpX = x;
                mLastWarpY = y;
                warp(pt[0], pt[1]);
                invalidate();
            }
            return true;
        }
    }
}