android - Android：如何扭曲图像？

Question

我想像这样扭曲图像：

添加 08-04-2013：我使用了这段代码，但它不能正常工作：

    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.ic_launcher);

        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;
    }

Answer 1

有一种比自己编写代码更简单的方法。请参阅TransitionDrawable

LayerDrawables 的扩展，旨在在第一层和第二层之间交叉淡入淡出。要开始转换，请调用 startTransition(int)。要仅显示第一层，请调用 resetTransition()。
它可以在带有 <transition> 元素的 XML 文件中定义。过渡中的每个 Drawable 都在嵌套的 <item> 中定义

你可以在网上找到很多例子，这里有一个：

<?xml version="1.0" encoding="utf-8"?>
<transition xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:drawable="@drawable/first_image" />
  <item android:drawable="@drawable/second_image" />
</transition>

和代码

final ImageView image = (ImageView) findViewById(R.id.image);
final ToggleButton button = (ToggleButton) findViewById(R.id.button);
button.setOnClickListener(new OnClickListener() {
  @Override
  public void onClick(final View v) {
    TransitionDrawable drawable = (TransitionDrawable) image.getDrawable();
    if (button.isChecked()) {
      drawable.startTransition(500);
    } else {
      drawable.reverseTransition(500);
    }
  }
}); 

Answer 2

这可以通过 OpenCV 来实现，所以试试这个