图片的放大缩小

布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="zoomIn"
            android:text="放大" />

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="zoomOut"
            android:text="缩小" />

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="rotate"
            android:text="旋转" />

        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="inverse"
            android:text="镜像" />
    </LinearLayout>

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/qq" />

</LinearLayout>

代码

public class MainActivity extends Activity {

    private ImageView imageView;
    private Bitmap bitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = (ImageView) findViewById(R.id.imageView);
        bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.qq);
    }
    
    public void zoomIn(View v) {
        Bitmap newBitmap = Bitmap.createBitmap(bitmap.getWidth() * 2, bitmap.getHeight() * 2, bitmap.getConfig());    // 创建新的Bitmap, 指定大小
        Canvas canvas = new Canvas(newBitmap);        // 创建画布
        Matrix matrix = new Matrix();                // 创建模型
        matrix.postScale(2, 2);                        // 设置缩放比例, x轴和y轴都是2倍大小
        canvas.drawBitmap(bitmap, matrix, null);    // 参照matrix模型, 在画布上按照bitmap画
        
        imageView.setImageBitmap(newBitmap);        // 把新图片设置到ImageView中
        bitmap = newBitmap;                            // 记住新图片, 下次从这个图片操作
    }
    
    public void zoomOut(View v) {
        Bitmap newBitmap = Bitmap.createBitmap(bitmap.getWidth() / 2, bitmap.getHeight() / 2, bitmap.getConfig());
        Canvas canvas = new Canvas(newBitmap);    
        Matrix matrix = new Matrix();
        matrix.postScale(0.5f, 0.5f);    
        canvas.drawBitmap(bitmap, matrix, null);
        
        imageView.setImageBitmap(newBitmap);
        bitmap = newBitmap;    
    }
    
    public void rotate(View v) {
        Bitmap newBitmap = Bitmap.createBitmap(bitmap.getHeight(), bitmap.getWidth(), bitmap.getConfig());
        Canvas canvas = new Canvas(newBitmap);    
        Matrix matrix = new Matrix();
        matrix.postRotate(90, bitmap.getWidth() / 2, bitmap.getHeight() / 2);    
        canvas.drawBitmap(bitmap, matrix, null);
        
        imageView.setImageBitmap(newBitmap);
        bitmap = newBitmap;    
    }
    
    public void inverse(View v) {
        Bitmap newBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight() , bitmap.getConfig());
        Canvas canvas = new Canvas(newBitmap);    
        Matrix matrix = new Matrix();
        matrix.postScale(-1, 1);                        // -1 代表x轴做镜像(镜像之后图片会移动到左边)
        matrix.postTranslate(bitmap.getWidth(), 0);        // 向右移动
        canvas.drawBitmap(bitmap, matrix, null);
        
        imageView.setImageBitmap(newBitmap);
        bitmap = newBitmap;    
    }

}