android的几种渲染与裁剪

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ComposeShader;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.graphics.SweepGradient;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;

public class GameView extends View implements Runnable
{
	/* 声明Bitmap对象 */
	Bitmap	mBitQQ	= null;
	int		BitQQwidth	= 0;
	int		BitQQheight	= 0;
	
	Paint   mPaint = null;
	
	/* Bitmap渲染 */
	Shader mBitmapShader = null;
	
	/* 线性渐变渲染 */
	Shader mLinearGradient = null;
	
	/* 混合渲染 */
	Shader mComposeShader = null;
	
	/* 唤醒渐变渲染 */
	Shader mRadialGradient = null;
	
	/* 梯度渲染 */
	Shader mSweepGradient = null;
	
	
	ShapeDrawable mShapeDrawableQQ = null;
	
	public GameView(Context context)
	{
		super(context);
		
		/* 装载资源 */
		mBitQQ = ((BitmapDrawable) getResources().getDrawable(R.drawable.qq)).getBitmap();

		/* 得到图片的宽度和高度 */
		BitQQwidth = mBitQQ.getWidth();
		BitQQheight = mBitQQ.getHeight();
		
		/* 创建BitmapShader对象 */
		mBitmapShader = new BitmapShader(mBitQQ,Shader.TileMode.REPEAT,Shader.TileMode.MIRROR);
		
		/* 创建LinearGradient并设置渐变的颜色数组 */
		mLinearGradient = new LinearGradient(0,0,100,100,
											 new int[]{Color.RED,Color.GREEN,Color.BLUE,Color.WHITE},
											 null,Shader.TileMode.REPEAT);
		/* 这里笔者理解为“混合渲染”--大家可以有自己的理解，能明白这个意思就好*/
		mComposeShader = new ComposeShader(mBitmapShader,mLinearGradient,PorterDuff.Mode.DARKEN);
		
		/* 构建RadialGradient对象，设置半径的属性 */
		//这里使用了BitmapShader和LinearGradient进行混合
		//当然也可以使用其他的组合
		//混合渲染的模式很多，可以根据自己需要来选择
		mRadialGradient = new RadialGradient(50,200,50,
											 new int[]{Color.GREEN,Color.RED,Color.BLUE,Color.WHITE},
											 null,Shader.TileMode.REPEAT);
		/* 构建SweepGradient对象 */
		mSweepGradient = new SweepGradient(30,30,new int[]{Color.GREEN,Color.RED,Color.BLUE,Color.WHITE},null);

		mPaint = new Paint();
		
		/* 开启线程 */
		new Thread(this).start();
	}
	
	public void onDraw(Canvas canvas)
	{
		super.onDraw(canvas);
		
		//将图片裁剪为椭圆形
		/* 构建ShapeDrawable对象并定义形状为椭圆 */
		mShapeDrawableQQ = new ShapeDrawable(new OvalShape());

		/* 设置要绘制的椭圆形的东西为ShapeDrawable图片 */
		mShapeDrawableQQ.getPaint().setShader(mBitmapShader);
		
		/* 设置显示区域 */
		mShapeDrawableQQ.setBounds(0,0, BitQQwidth, BitQQheight);
		
		/* 绘制ShapeDrawableQQ */
		mShapeDrawableQQ.draw(canvas); 		
		
		//绘制渐变的矩形
		mPaint.setShader(mLinearGradient);
		canvas.drawRect(BitQQwidth, 0, 320, 156, mPaint);
	
		//显示混合渲染效果
		mPaint.setShader(mComposeShader);
		canvas.drawRect(0, 300, BitQQwidth, 300+BitQQheight, mPaint);
		
		//绘制环形渐变
		mPaint.setShader(mRadialGradient);
		canvas.drawCircle(50, 200, 50, mPaint);
		
		//绘制梯度渐变
		mPaint.setShader(mSweepGradient);
		canvas.drawRect(150, 160, 300, 300, mPaint);
		
	}
	
	// 触笔事件
	public boolean onTouchEvent(MotionEvent event)
	{
		return true;
	}


	// 按键按下事件
	public boolean onKeyDown(int keyCode, KeyEvent event)
	{
		return true;
	}


	// 按键弹起事件
	public boolean onKeyUp(int keyCode, KeyEvent event)
	{
		return false;
	}


	public boolean onKeyMultiple(int keyCode, int repeatCount, KeyEvent event)
	{
		return true;
	}
	
	
	/**
	 * 线程处理
	 */
	public void run()
	{
		while (!Thread.currentThread().isInterrupted())
		{
			try
			{
				Thread.sleep(100);
			}
			catch (InterruptedException e)
			{
				Thread.currentThread().interrupt();
			}
			//使用postInvalidate可以直接在线程中更新界面
			postInvalidate();
		}
	}
}

 还有一些形状处理的类在

android.graphics.drawable.shapes包下