前一篇文章讲述了Android触屏setOnTouchListener实现突破缩放、移动、绘制和加入水印,继续我的"随手拍"项目完毕给图片加入相框、圆形圆角显示图片和图像合成的功能介绍.希望文章对大家有所帮助.

一. 打开图片和显示assets文件里图片

    首先,对XML中activity_main.xml进行布局,通过使用RelativeLayout相对布局完毕(XML代码后面附).然后,在Mainctivity.java中public class MainActivity extends Activity函数加入代码例如以下,加入点击button监听事件：

//控件 
private Button openImageBn;            //打开图片
private Button showImageBn;            //显示assets资源图片
private Button showImageBn1;           //模式1加成
private Button showImageBn2;           //模式2加成
private Button roundImageBn;           //圆角图片
private ImageView imageShow;           //显示图片
//自己定义变量
private Bitmap bmp;                    //原始图片
private final int IMAGE_OPEN = 0;      //打开图片
private Canvas canvas;                 //画布
private Paint paint;                   //画刷
		
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
	//打开图片
	openImageBn = (Button)findViewById(R.id.button1);
	imageShow = (ImageView) findViewById(R.id.imageView1);
	openImageBn.setOnClickListener(new OnClickListener() {
		@Override
		public void onClick(View v) {		 
			Intent intent = new Intent(Intent.ACTION_PICK, 
					android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
			startActivityForResult(intent, IMAGE_OPEN);
		}
	});
    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }
}
//打开图片
protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
	 super.onActivityResult(requestCode, resultCode, data);  
	 if(resultCode==RESULT_OK && requestCode==IMAGE_OPEN) {  
    	Uri imageFileUri = data.getData();
    	DisplayMetrics dm = new DisplayMetrics();
    	getWindowManager().getDefaultDisplay().getMetrics(dm);  
        int width = dm.widthPixels;    //手机屏幕水平分辨率   
        int height = dm.heightPixels;  //手机屏幕垂直分辨率
	    try {  
	        //加载图片尺寸大小没加载图片本身 true
	        BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();  
	        bmpFactoryOptions.inJustDecodeBounds = true;  
	        bmp = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageFileUri), null, bmpFactoryOptions);  
	        int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)height);  
	        int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)width);    
	        //inSampleSize表示图片占原图比例 1表示原图
	        if(heightRatio>1&&widthRatio>1) {  
	            if(heightRatio>widthRatio) {  
	                bmpFactoryOptions.inSampleSize = heightRatio;  
	            }  
	            else {  
	                bmpFactoryOptions.inSampleSize = widthRatio;  
	            }  
	        }  		            
	        //图像真正解码 false
	        bmpFactoryOptions.inJustDecodeBounds = false;                 
	        bmp = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageFileUri), null, bmpFactoryOptions);    
	        imageShow.setImageBitmap(bmp);
	    }
	    catch(FileNotFoundException e) { 
	        e.printStackTrace();  
	    } 
	}  //end if
}

    上面点击"打开"button能实现打开图片,而在讲述为图片加入边框时,它事实上就是通过两张或多张图片的合成实现的.
    在jacpy.may《Android图片处理总结》文档中建议图片不要放在drawable文件夹下,由于屏幕分辨率会影响图片的大小.最好放在assets文件夹里,它代表应用无法直接訪问的原生资源(通常载入PNG透明图实现边框合成),仅仅能以流的方式读取而且小于1M.
    读取assets文件夹中图片的方法例如以下,首先手动加入PNG图片至assets文件夹,然后在omCreate函数中加入例如以下代码：

//显示assets中图片
showImageBn = (Button)findViewById(R.id.button2);
showImageBn.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {		 
		Bitmap bitmap = getImageFromAssets("image01.png");
		imageShow.setImageBitmap(bitmap);  
	}
});

//获取assets中资源并转换为Bitmap
private Bitmap getImageFromAssets(String fileName)
{
	//Android中使用assets文件夹存放资源,它代表应用无法直接訪问的原生资源
	Bitmap imageAssets = null;
	AssetManager am = getResources().getAssets();
	try {
		InputStream is = am.open(fileName);
		imageAssets = BitmapFactory.decodeStream(is);
		is.close();
	} catch(IOException e) {
		e.printStackTrace();
	}
	return imageAssets;
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.touchimagetest.MainActivity"
    tools:ignore="MergeRootFrame" >
    <!-- 底部加入按钮 -->
    <RelativeLayout
        android:id="@+id/MyLayout_bottom"
        android:orientation="horizontal" 
        android:layout_width="fill_parent"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:gravity="center">
	    <LinearLayout 
	        android:layout_width="match_parent"
	    	android:layout_height="match_parent"
	    	android:orientation="horizontal"
	    	android:layout_alignParentBottom="true" >
			<Button
				 android:id="@+id/button1"
				 android:layout_width="wrap_content"
				 android:layout_height="match_parent"
				 android:layout_weight="1"
				 android:text="打开" />
			<Button
				 android:id="@+id/button2"
				 android:layout_width="wrap_content"
				 android:layout_height="match_parent"
				 android:layout_weight="1"
				 android:text="显示" />
			<Button
				 android:id="@+id/button3"
				 android:layout_width="wrap_content"
				 android:layout_height="match_parent"
				 android:layout_weight="1"
				 android:text="边框" />
			<Button
				 android:id="@+id/button4"
				 android:layout_width="wrap_content"
				 android:layout_height="match_parent"
				 android:layout_weight="1"
				 android:text="桃心" />
			<Button
				 android:id="@+id/button5"
				 android:layout_width="wrap_content"
				 android:layout_height="match_parent"
				 android:layout_weight="1"
				 android:text="圆形" />
	    </LinearLayout>
	</RelativeLayout>
    <!-- 顶部显示图片 -->
    <RelativeLayout
        android:id="@+id/Content_Layout" 
        android:orientation="horizontal"
        android:layout_above="@id/MyLayout_bottom"
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"
      	android:layout_alignParentTop="true"
        android:background="#000000"
        android:gravity="center">
        <ImageView
	        android:id="@+id/imageView1"
	        android:layout_width="fill_parent"
	        android:layout_height="fill_parent"
	        android:layout_gravity="center_horizontal" />
    </RelativeLayout>
</RelativeLayout>

二. 加入相框与图片合成

//模式1合成图片
showImageBn1 = (Button)findViewById(R.id.button3);
showImageBn1.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		Bitmap bitmap = getImageFromAssets("image01.png");
		addFrameToImage(bitmap);
	}
});

//图片合成1
private void addFrameToImage(Bitmap bm) //bmp原图(前景) bm资源图片(背景)
{
	Bitmap drawBitmap =Bitmap.createBitmap(bmp.getWidth(),
			bmp.getHeight(), bmp.getConfig());
	canvas = new Canvas(drawBitmap);
	paint = new Paint();
	canvas.drawBitmap(bmp, 0, 0, paint);
	paint.setXfermode(new PorterDuffXfermode(android.
			graphics.PorterDuff.Mode.LIGHTEN));
	//对边框进行缩放
    int w = bm.getWidth();
    int h = bm.getHeight();
    //缩放比 假设图片尺寸超过边框尺寸 会自己主动匹配
    float scaleX = bmp.getWidth()*1F / w;      
    float scaleY = bmp.getHeight()*1F / h;
    Matrix matrix = new Matrix();
    matrix.postScale(scaleX, scaleY);   //缩放图片
    Bitmap copyBitmap =  Bitmap.createBitmap(bm, 0, 0, w, h, matrix, true);
	canvas.drawBitmap(copyBitmap, 0, 0, paint);
	imageShow.setImageBitmap(drawBitmap);	
}

//模式2合成图片
showImageBn2 = (Button)findViewById(R.id.button4);
showImageBn2.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		Bitmap bitmap = getImageFromAssets("image07.png");
		//另外一种合成方法
		imageShow.setImageBitmap(addFrameToImageTwo(bitmap));
	}
});

//图片合成	
private Bitmap addFrameToImageTwo(Bitmap frameBitmap) //bmp原图 frameBitmap资源图片(边框)
{
	//bmp原图 创建新位图
	int width = bmp.getWidth();  
    int height = bmp.getHeight();
    Bitmap drawBitmap =Bitmap.createBitmap(width, height, Config.RGB_565);
	//对边框进行缩放
    int w = frameBitmap.getWidth();
    int h = frameBitmap.getHeight();
    float scaleX = width*1F / w;        //缩放比 假设图片尺寸超过边框尺寸 会自己主动匹配
    float scaleY = height*1F / h;
    Matrix matrix = new Matrix();
    matrix.postScale(scaleX, scaleY);   //缩放图片
    Bitmap copyBitmap =  Bitmap.createBitmap(frameBitmap, 0, 0, w, h, matrix, true);
    
    int pixColor = 0;  
    int layColor = 0;  
    int newColor = 0;
    
    int pixR = 0;  
    int pixG = 0;  
    int pixB = 0;  
    int pixA = 0;  
      
    int newR = 0;  
    int newG = 0;  
    int newB = 0;  
    int newA = 0;  
      
    int layR = 0;  
    int layG = 0;  
    int layB = 0;  
    int layA = 0;  
      
    float alpha = 0.8F; 
    float alphaR = 0F;  
    float alphaG = 0F;  
    float alphaB = 0F;
    
    for (int i = 0; i < width; i++)  
    {  
        for (int k = 0; k < height; k++)  
        {  
            pixColor = bmp.getPixel(i, k);  
            layColor = copyBitmap.getPixel(i, k);  
            // 获取原图片的RGBA值   
            pixR = Color.red(pixColor);  
            pixG = Color.green(pixColor);  
            pixB = Color.blue(pixColor);  
            pixA = Color.alpha(pixColor);  
            // 获取边框图片的RGBA值   
            layR = Color.red(layColor);  
            layG = Color.green(layColor);  
            layB = Color.blue(layColor);  
            layA = Color.alpha(layColor);  
            // 颜色与纯黑色相近的点   
            if (layR < 20 && layG < 20 && layB < 20)  
            {  
                alpha = 1F;  
            }  
            else  
            {  
                alpha = 0.3F;  
            }  
            alphaR = alpha;  
            alphaG = alpha;  
            alphaB = alpha;  
            // 两种颜色叠加   
            newR = (int) (pixR * alphaR + layR * (1 - alphaR));  
            newG = (int) (pixG * alphaG + layG * (1 - alphaG));  
            newB = (int) (pixB * alphaB + layB * (1 - alphaB));  
            layA = (int) (pixA * alpha + layA * (1 - alpha));  
            // 值在0~255之间   
            newR = Math.min(255, Math.max(0, newR));  
            newG = Math.min(255, Math.max(0, newG));  
            newB = Math.min(255, Math.max(0, newB));  
            newA = Math.min(255, Math.max(0, layA));  
            //绘制 
            newColor = Color.argb(newA, newR, newG, newB);  
            drawBitmap.setPixel(i, k, newColor);  
        }  
    }  
    return drawBitmap;
}

   它的执行效果例如以下所看到的,当中前2附图是方法一,可是它的合成效果不是非常优秀,而第三张图是另外一种方法,可是它的响应时间略微要长些.
            

   在第一种方法通过PoterDuffXfermode类作为过渡模式,该类因Thomas Porter和Tom Duff而得名,他们于1984年在ACM SIGGRAPH计算机图形学发表“Compositing digital images(合成数字图像)”的文章,它介绍了彼此重叠绘制图像的不同规则.这些规则定义了哪些图像的哪些部分将出如今结果输出中.
    在Android的PorterDuff.Mode类中列举了Porter和Duff及其它很多其它人制定的规则.
    android.graphics.PorterDuff.Mode.SRC:此规则意味着仅仅绘制源图像,当前它正是应用此规则的Paint对象.
    android.graphics.PorterDuff.Mode.DST:此规则意味着仅仅显示目标图像,在已有画布上的初始图像.
    例如以下图所看到的,定义Mode值例如以下：
                                   
    当中,有4个规则定义了当一幅图像放置在还有一幅图像上时怎样合成这两幅图像,它是我们常常使用的值：
    android.graphics.PorterDuff.Mode.LIGHTEN:获得每一个位置上两幅图像中最亮的像素并显示.
    android.graphics.PorterDuff.Mode.DARKEN:获得每一个位置上两幅图像中最暗的像素并显示.
    android.graphics.PorterDuff.Mode.MULTIPLY:将每一个位置的两个像素相乘,除以255,使用该值创建一个新的像素进行显示.结果颜色=顶部颜色*底部颜色/255.
    android.graphics.PorterDuff.Mode.SCREEN:反转每一个颜色,运行同样操作.结果颜色=255-(((255-顶部颜色)*(255-底部颜色))/255)

三. 圆形和圆角矩形显示图片

//圆角合成图片
roundImageBn = (Button)findViewById(R.id.button5);
roundImageBn.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		imageShow.setImageBitmap(getRoundedCornerBitmap(bmp) );
	}
});

//生成圆角图片
private Bitmap getRoundedCornerBitmap(Bitmap bitmap) 
{
	Bitmap roundBitmap = Bitmap.createBitmap(bitmap.getWidth(), 
         bitmap.getHeight(), Config.ARGB_8888); 
     Canvas canvas = new Canvas(roundBitmap); 
     int color = 0xff424242; 
     Paint paint = new Paint(); 
     //设置圆形半径
     int radius; 
     if(bitmap.getWidth()>bitmap.getHeight()) {
    	 radius = bitmap.getHeight()/2;
     }
     else {
    	 radius = bitmap.getWidth()/2;
     }
     //绘制圆形
     paint.setAntiAlias(true); 
     canvas.drawARGB(0, 0, 0, 0); 
     paint.setColor(color); 
     canvas.drawCircle( bitmap.getWidth()/ 2, bitmap.getHeight() / 2, radius, paint);
     paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN)); 
     canvas.drawBitmap(bitmap, 0, 0, paint);
     return roundBitmap; 
}

private Bitmap getRoundedCornerBitmap(Bitmap bitmap) 
{
	//绘制圆角矩形
	Bitmap roundBitmap = Bitmap.createBitmap(bitmap.getWidth(), 
         bitmap.getHeight(), Config.ARGB_8888); 
     Canvas canvas = new Canvas(roundBitmap); 
     int color = 0xff424242; 
     Paint paint = new Paint(); 
     Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight()); 
     RectF rectF = new RectF(rect); 
     float roundPx = 80;      //转角设置80
     //绘制
     paint.setAntiAlias(true); 
     canvas.drawARGB(0, 0, 0, 0); 
     paint.setColor(color); 
     canvas.drawRoundRect(rectF, roundPx, roundPx, paint); 
     paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN)); 
     canvas.drawBitmap(bitmap, rect, rect, paint); 
}

   执行结果例如以下图所看到的：