Android API之图像扭曲效果

/**
* Android API之图像扭曲效果
* @description：
* @date 2016-7-22 下午2:19:12
*/
public class BitmapMesh extends GraphicsActivity {

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

private static class SampleView extends View {
//定义常量,指定该图片横向被划分为20格
private static final int WIDTH = 20;
//定义常量,指定该图片纵向上被划分为20格
private static final int HEIGHT = 20;
//记录该图像上包含441个顶点
private static final int COUNT = (WIDTH + 1) * (HEIGHT + 1);
//位图
private final Bitmap mBitmap;
//数组,记录Bitmap上的21*21个点的坐标
private final float[] mVerts = new float[COUNT * 2];
//记录Bitmap上的21*21个点经过扭曲后的坐标
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);
//加载图片
mBitmap = BitmapFactory.decodeResource(getResources(), R.raw.beach);
//获取图像的宽度和高度
float w = mBitmap.getWidth();
float h = mBitmap.getHeight();
//构建扭曲数据
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;
//初始化orig,verts数组
//初始化,orig,verts两个数组均匀地保存了21 * 21个点的x,y坐标　
setXY(mVerts, index, fx, fy);
setXY(mOrig, index, fx, fy);
index += 1;
}
}
//设置平移效果
mMatrix.setTranslate(10, 10);
//实现乱矩阵逆向坐标映射
mMatrix.invert(mInverse);
}

@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(0xFFCCCCCC);
//对matrix的变换应用到canvas上的所有对象.
canvas.concat(mMatrix);
/**
* bitmap　　　　    　需要扭曲的源位图
* meshWidth 　　控制在横向上把该源位图划成成多少格
* meshHeight　  　 控制在纵向上把该源位图划成成多少格
* verts 　　　　　    长度为(meshWidth + 1) * (meshHeight + 1) * 2的数组，它记录了扭曲后的位图各顶点位置
* vertOffset    控制verts数组中从第几个数组元素开始才对bitmap进行扭曲
*/
canvas.drawBitmapMesh(mBitmap, WIDTH, HEIGHT, mVerts, 0, null, 0,
null);
}
//根据触摸事件的位置计算verts数组里各元素的值
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;
//计算每个坐标点与当前点(cx,cy)之间的距离
float d = FloatMath.sqrt(dd);
//扭曲度，距离当前点(cx,cy)越远，扭曲度越小
float pull = K / (dd + 0.000001f);
pull /= (d + 0.000001f);
//对dst数组(保存bitmap　上21 * 21个点经过扭曲后的坐标)赋值
if (pull >= 1) {
dst[i + 0] = cx;
dst[i + 1] = cy;
} else {
//控制各顶点向触摸事件发生点偏移
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;

@SuppressLint("ClickableViewAccessibility") @Override
public boolean onTouchEvent(MotionEvent event) {
float[] pt = { event.getX(), event.getY() };
//用当前矩阵改变pts中的值，然后存储在pts中，同上，pts也是存储点的坐标的数组
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;
}
}
}