调用内置的Gallery查看SD卡中的图片，点击图片并回传，通过缩放与模拟器尺寸大小相适应并进行显示。

MainActivity.java

public class MainActivity extends Activity implements OnClickListener {

    private Button gallery;
    private ImageView img,img2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        iviview();
    }

    private void iviview() {
        gallery = (Button) findViewById(R.id.gallery);
        img = (ImageView) findViewById(R.id.img);
        img2 = (ImageView) findViewById(R.id.img2);
        gallery.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if (v == gallery) {
            Intent i = new Intent(
                    Intent.ACTION_PICK,
                    android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
            startActivityForResult(i, 0);
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 0) {
            if (resultCode == RESULT_OK) {
                // 获得地址
                Uri imguri = data.getData();
                // 获得模拟器的宽和高
                Display imgdp = getWindowManager().getDefaultDisplay();
                int wd = imgdp.getWidth()/2;
                int hd = imgdp.getHeight()/2-100;
                // 我们要获得 图片的尺寸，如果图片很大 可能会导致图片溢出
                // 加载图片并非是图片本身
                BitmapFactory.Options bo = new BitmapFactory.Options();
                bo.inJustDecodeBounds = true;
                // 这里的流需要转换
                try {
                    Bitmap bmp = BitmapFactory.decodeStream(
                            getContentResolver().openInputStream(imguri), null,
                            bo);
                    // 现在我们获得图片与模拟器的比例
                    int wdbili = (int) Math.ceil((float) bo.outWidth
                            / (float) wd);
                    int hdbili = (int) Math.ceil((float) bo.outHeight
                            / (float) hd);
                    // 判断比例大于1
                    if (wdbili > 1 || hdbili > 1) {
                        // 我们判断比例大小
                        if (wdbili > hdbili) {
                            bo.inSampleSize = wdbili;
                        } else {
                            bo.inSampleSize = hdbili;
                        }
                    }
                    // 处理完之后 我们还要从新加载图片
                    bo.inJustDecodeBounds = false;
                    bmp = BitmapFactory.decodeStream(getContentResolver()
                            .openInputStream(imguri), null, bo);
                    //在位图上绘制一张图片
                    Bitmap upbmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
                    //我们创建一张画布
                    Canvas cv = new Canvas(upbmp);
                    //我们创建一个笔
                    Paint paint = new Paint();
                    
                    //我们要用笔进行绘制
                    //cv.drawBitmap(bmp, 0, 0, paint);
                    
                    //创建一个matrix , 进行大小改变
                    Matrix matrix = new Matrix();
                    matrix.setValues(new float[]{
                            0.5f,0,0,
                            0,0.5f,0,
                            0,0,0.5f
                    });
                    
                    //旋转(正数顺时针，负数逆时针)
                    matrix.setRotate(30);
                    //固定哪一个点进行旋转
                    matrix.setRotate(30);
                    matrix.setRotate(30, upbmp.getWidth(), upbmp.getHeight());
                    
                    //平移
                    matrix.setTranslate(20, 20);
                    
                    //缩放(倍数)
                    matrix.setScale(1.5f, 2);

                   //镜像的感觉
                    matrix.setScale(-1, 1);
                    matrix.postTranslate(upbmp.getWidth(), 0);

                    //倒立
                    matrix.setScale(1, -1);
                    matrix.postTranslate(0, upbmp.getHeight());

                    //我们通过matrix进行改变图片大小
                    cv.drawBitmap(bmp, matrix, paint);
                    //进行显示
                    img.setImageBitmap(bmp);
                    //进行显示
                    img2.setImageBitmap(upbmp);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

activity_main.xml

<RelativeLayout 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: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" >

     <Button
         android:id="@+id/gallery"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentTop="true"
         android:layout_marginLeft="24dp"
         android:text="打开画廊" />

     <ImageView
         android:id="@+id/img"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignLeft="@+id/gallery"
         android:layout_below="@+id/gallery"
         android:layout_marginTop="20dp"
         />

     <ImageView
         android:id="@+id/img2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignLeft="@+id/gallery"
         android:layout_below="@+id/gallery"
         android:layout_marginTop="20dp"
         />


</RelativeLayout>