Android 倒影实现算法

http://ysl-paradise.blogspot.com/2009/12/ii.html

public class MirrorView extends View {
Paintm_paint;
int m_nShadowH;
Drawable m_dw;
Bitmap m_bitmap;

//xxxx
Matrix mMatrix;
int shadowHeight;

public MirrorView(Context context, Bitmap bitmap) {
super(context);
m_bitmap = bitmap;
_Init();

// TODO Auto-generated constructor stub
}

private void _Init() {
//m_dw = new BitmapDrawable(BitmapFactory.decodeResource(getResources(), R.drawable.icon));
m_dw = new BitmapDrawable(m_bitmap);
m_dw.setBounds(0,0,m_dw.getIntrinsicWidth(),m_dw.getIntrinsicHeight());
m_nShadowH = m_dw.getIntrinsicHeight()/1;
m_paint = new Paint(Paint.ANTI_ALIAS_FLAG);
LinearGradient lg = new LinearGradient(0, 0, 0, m_nShadowH, 0xB0FFFFFF, 0x00000000, Shader.TileMode.CLAMP);
m_paint.setShader(lg);
m_paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY));

//xxxx
mMatrix = new Matrix();
}

@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
int nX = 0;
int nY = 0;
_DrawNormalImg(canvas, nX, nY);
_DrawMirror(canvas, nX, nY);
}

private void _DrawNormalImg(Canvas canvas, int nX, int nY) {
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.translate(nX, nY);
m_dw.draw(canvas);
canvas.restore();
}

private void _DrawMirror(Canvas canvas, int nX, int nY) {
int nW = m_dw.getIntrinsicWidth();
int nH = m_dw.getIntrinsicHeight();
//U.dout("nW="+nW+",nH="+nH);

//xxxx
shadowHeight=nH/2;

//xxxx
float[] src={0, nH, nW, nH, nW,nH - m_nShadowH, 0, nH - m_nShadowH};
float[] dst={ 0, nH, nW, nH,nW, shadowHeight, 0, shadowHeight };

//xxxx
canvas.save();
mMatrix.setPolyToPoly(src, 0, dst, 0, src.length >> 1);
canvas.concat(mMatrix);

//draw mirror image
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.scale(1.0f, -1.0f);
canvas.translate(nX, -(nY + nH * 2));
canvas.clipRect(0, nH, nW, nH - m_nShadowH);
m_dw.draw(canvas);
canvas.restore();

//draw mask
canvas.save();
canvas.translate(nX, nY + nH);
canvas.drawRect(0, 0, nW, m_nShadowH, m_paint);
canvas.restore();

//xxxx
canvas.restore();
}

}

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