Android学习笔记_66_图片处理专题

　　1、图片缩放：不解析整个图片信息。

public class DemoActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ImageView iv = (ImageView) this.findViewById(R.id.iv);
//        BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
//        //按1/8的大小加载到内存
//        bmpFactoryOptions.inSampleSize = 8;
//        Bitmap bm = BitmapFactory.decodeFile("/sdcard/img.jpg",bmpFactoryOptions);
//        iv.setImageBitmap(bm);

        //
        //1. 首先得到屏幕的宽高
        Display currentDisplay = getWindowManager().getDefaultDisplay();
        int dw = currentDisplay.getWidth();
        int dh = currentDisplay.getHeight();
        // 2. 获取图片的宽度和高度
        BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
        // 设置inJustDecodeBounds = true ,只会解析文件头信息;
        bmpFactoryOptions.inJustDecodeBounds = true;
        // 不会真正的解析这个位图
        Bitmap bmp = BitmapFactory.decodeFile("/sdcard/img.jpg", bmpFactoryOptions);
        //得到图片的宽度和高度
        int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)dh);
        int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)dw);
        Log.v("HEIGHTRATIO",""+heightRatio);
        Log.v("WIDTHRATIO",""+widthRatio);

        //真正的解析位图
        bmpFactoryOptions.inJustDecodeBounds = false;

        if(heightRatio>widthRatio){
            bmpFactoryOptions.inSampleSize = heightRatio;
        }else{
            bmpFactoryOptions.inSampleSize = widthRatio;
        }
        bmp = BitmapFactory.decodeFile("/sdcard/img.jpg", bmpFactoryOptions);

        iv.setImageBitmap(bmp);
    }
}

　　2、ExifInterface获取或设置图片的exif信息：

public class DemoActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        try {
            ExifInterface  exif = new ExifInterface("sdcard/img.jpg");
            System.out.println( exif.getAttribute(ExifInterface.TAG_DATETIME));
            System.out.println( exif.getAttribute(ExifInterface.TAG_IMAGE_LENGTH));
            System.out.println( exif.getAttribute(ExifInterface.TAG_IMAGE_WIDTH));
            exif.setAttribute("camera", "柯达相机");
            System.out.println( exif.getAttribute("camera"));
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

3、从图库里面选择一个图片，然后将它设置到ImageView。

public class DemoActivity extends Activity {
    ImageView iv;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        iv = (ImageView) this.findViewById(R.id.iv);
    }

    public void click(View view){
        //选择图库意图，打开图库
        Intent intent = new Intent(Intent.ACTION_PICK);
        intent.setType("image/*");
        startActivityForResult(intent, 0);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(data!=null){
            //图片的uri
            Uri uri = data.getData() ;
            iv.setImageURI(uri);
        }
        super.onActivityResult(requestCode, resultCode, data);
    }
}

　　4、创建图片（bitmap）的拷贝：

public class DemoActivity extends Activity{
    ImageView iv1;
    ImageView iv2;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        iv1= (ImageView) this.findViewById(R.id.iv1);
        iv2= (ImageView) this.findViewById(R.id.iv2);
    }

    public void click(View view){
        Intent intent = new Intent(Intent.ACTION_PICK);
        intent.setType("image/*");
        startActivityForResult(intent, 0);
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(data!=null){
            //图片的uri
            Uri uri = data.getData() ;
            iv1.setImageURI(uri);
            // 获取第一个图片 的拷贝 设置到iv2的控件里面
            try {
                //通过uri获取一个流对象。getContentResolver().openInputStream(uri)
                Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
                //图片缩放
                Matrix matrix = new Matrix();
//                matrix.setValues(new float[] {
//                    2, 0, 0,
//                    0, 1, 0,
//                    0, 0, 1
//                });//矩阵缩放
//                matrix.setScale(1.5f, 1.0f);//水平方向为1.5倍，垂直方向不做改变
//                matrix.postTranslate(bitmap.getWidth(), 1.0f);//与setScale可以实现图片翻转
//                matrix.setRotate(30);
                //画笔
                Paint paint = new Paint();
                paint.setAntiAlias(true);//消除锯齿
                matrix.setRotate(15);//图片旋转
                //得到一个大小 配置跟原图一样的空白的位图
                //Bitmap  alterbitmap  = Bitmap.createBitmap(bitmap.getWidth()*2, bitmap.getHeight(), bitmap.getConfig());
                Bitmap    alteredBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(),
                        matrix, false);
                //画布对象
                Canvas canvas = new Canvas();
                //将图片流bitmap应用到画布上
                canvas.drawBitmap(bitmap, matrix, paint);
                iv2.setImageBitmap(alteredBitmap);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        super.onActivityResult(requestCode, resultCode, data);
    }
}

最后一个：filter解释
true if the source should be filtered. Only applies if the matrix contains more than just translation.
当进行的不只是平移变换时，filter参数为true可以进行滤波处理，有助于改善新图像质量;flase时，计算机不做过滤处理。

图片裁剪，可用这个方法：
Bitmap source：要从中截图的原始位图
int x: 起始x坐标
int y：起始y坐标
int width： 要截的图的宽度
int height：要截的图的高度

要想imageView.setImageMatrix()方法起作用，xml得配置android:scaleType="matrix"

matrix.setRotate和matrix.postRotate的区别：
post...：平移、旋转等效果可以叠加在一起；
set...：前一种效果会消失，只有后来的操作，即它会重置Matrix

　

　5、图片合成：

public class DemoActivity extends Activity {
   Bitmap basebitmap;
   Canvas canvas ;
   Paint paint;
   ImageView iv;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        iv = (ImageView) this.findViewById(R.id.iv);
    }
    public void select1(View view){
        Intent intent = new Intent(Intent.ACTION_PICK);
        intent.setType("image/*");
        startActivityForResult(intent, 10);
        // 从图库里面获取第一个图片
    }
    public void save(View view){
        File file = new File("/sdcard/1.jpg");
        FileOutputStream fos;
        try {
            fos = new FileOutputStream(file);
            basebitmap.compress(CompressFormat.JPEG, 100, fos);
            //显示的发送一条广播
            //sd卡挂载的广播
            Intent intent = new Intent(Intent.ACTION_MEDIA_MOUNTED,Uri.parse("file://"+Environment.getExternalStorageDirectory()));
            sendBroadcast(intent);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    public void select2(View view){
           Intent intent = new Intent(Intent.ACTION_PICK);
        intent.setType("image/*");
        startActivityForResult(intent, 20);
        // 从图库里面获取第一个图片
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(requestCode==10){
            if(data!=null){
                Uri uri = data.getData();
                try {
                    Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));

                    basebitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig());
                    canvas = new Canvas(basebitmap);
                    paint = new Paint();
                    canvas.drawBitmap(bitmap, 0, 0, paint);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }else if(requestCode==20){
            if(data!=null){
                Uri uri = data.getData();
                //把第二张位图的内容 画在 basebitmap上
                try {
                    Bitmap bitmap = BitmapFactory.decodeStream(  getContentResolver().openInputStream(uri));
                    paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.MULTIPLY));
                    canvas.drawBitmap(bitmap, 0,0, paint);
                    iv.setImageBitmap(basebitmap);
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        }
        super.onActivityResult(requestCode, resultCode, data);
    }
}

　　6、根据路径Path绘制文字：

public class DemoActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new MyView(this));
    }
    private class MyView extends View{
        public MyView(Context context) {
            super(context);
        }
        @Override
        protected void onDraw(Canvas canvas) {

            Paint paint = new Paint();
            paint.setColor(Color.GREEN);
            paint.setTextSize(20);
            paint.setTypeface(Typeface.DEFAULT);
            Path p = new Path();
            p.moveTo(20, 20);
            p.lineTo(100, 150);
            p.lineTo(200, 220);
            canvas.drawTextOnPath("Hello this is text on a path", p, 0, 0, paint);
            super.onDraw(canvas);
        }
    }
}

　　7、绘图（根据手指移动创建图片并保存）：

public class DemoActivity extends Activity {
    ImageView iv;
    Bitmap bitmap;
    Canvas canvas;
    Paint paint;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        iv = (ImageView) this.findViewById(R.id.iv);
        Display diaplay = getWindow().getWindowManager().getDefaultDisplay();
        int height = diaplay.getHeight() - 40;
        int width = diaplay.getWidth();
        bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        iv.setImageBitmap(bitmap);
        canvas = new Canvas(bitmap);
        paint= new Paint();
        paint.setColor(Color.GREEN);
        paint.setStrokeWidth(10);
        iv.setOnTouchListener(new OnTouchListener() {

            float startx = 0;
            float starty = 0;

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    startx =  event.getX();
                    starty =  event.getY();

                    break;
                case MotionEvent.ACTION_MOVE:
                    float x =  event.getX();
                    float y =  event.getY();
                    canvas.drawLine(startx, starty, x, y, paint);
                    startx =  event.getX();
                    starty =  event.getY();

                    //通知imageview更新界面
                    iv.invalidate();
                    break;
                case MotionEvent.ACTION_UP:
                    float endx =  event.getX();
                    float endy =  event.getY();
                    canvas.drawLine(startx, starty, endx, endy, paint);
                    //通知imageview更新界面
                    iv.invalidate();
                    break;
                default:
                    break;
                }

                return true;
            }
        });

    }

    public void save(View view) {
        File file = new File("/sdcard/"+System.currentTimeMillis()+".jpg");
        FileOutputStream fos;
        try {
            fos = new FileOutputStream(file);

            bitmap.compress(CompressFormat.JPEG, 100, fos);
            //显示的发送一条广播
            //sd卡挂载的广播
            Intent intent = new Intent(Intent.ACTION_MEDIA_MOUNTED,Uri.parse("file://"+Environment.getExternalStorageDirectory()));
            sendBroadcast(intent);

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

8、矩阵Matrix

Matrix的操作，总共分为translate（平移），rotate（旋转），scale（缩放）和skew（倾斜）四种，每一种变换在Android的API里都提供了set, post和pre三种操作方式,除了translate，其他三种操作都可以指定中心点。
set是直接设置Matrix的值，每次set一次，整个Matrix的数组都会变掉。
post是后乘，当前的矩阵乘以参数给出的矩阵。可以连续多次使用post，来完成所需的整个变换。

例如，要将一个图片旋转30度，然后平移到(100,100)的地方，那么可以这样做:

Matrix m =  new  Matrix();
m.postRotate(30 );
m.postTranslate(100 ,  100 ); 

pre是前乘，参数给出的矩阵乘以当前的矩阵。所以操作是在当前矩阵的最前面发生的。例如上面的例子，如果用pre的话

Matrix m =  new  Matrix();
m.setTranslate(100 ,  100 );
m.preRotate(30 )

旋转、缩放和倾斜都可以围绕一个中心点来进行，如果不指定，默认情况下，是围绕(0,0)点来进行。

public   class  MyView  extends  View {  

    private  Bitmap mBitmap;
    private  Matrix mMatrix =  new  Matrix();  

    public  MyView(Context context) {
        super (context);
        initialize();
    }  

    private   void  initialize() {  

        Bitmap bmp = ((BitmapDrawable)getResources().getDrawable(R.drawable.show)).getBitmap();
        mBitmap = bmp;
        /*首先，将缩放为100*100。这里scale的参数是比例。有一点要注意，如果直接用100/
bmp.getWidth()的话，会得到0，因为是整型相除，所以必须其中有一个是float型的，直接用100f就好。*/
        mMatrix.setScale(100f/bmp.getWidth(), 100f/bmp.getHeight());
                //平移到（100，100）处
        mMatrix.postTranslate(100 ,  100 );
                //倾斜x和y轴，以（100，100）为中心。
        mMatrix.postSkew(0 .2f,  0 .2f,  100 ,  100 );
    }  

    @Override   protected   void  onDraw(Canvas canvas) {
//      super.onDraw(canvas);  //如果界面上还有其他元素需要绘制，只需要将这句话写上就行了。   

        canvas.drawBitmap(mBitmap, mMatrix, null );
    }
}  

pre方法表示矩阵前乘，例如：变换矩阵为A，原始矩阵为B，pre方法的含义即是A*B

post方法表示矩阵后乘，例如：变换矩阵为A，原始矩阵为B，post方法的含义即是B*A

matrix.preScale(0.5f, 1);
matrix.preTranslate(10, 0);
matrix.postScale(0.7f, 1);
matrix.postTranslate(15, 0);
等价于：

translate(10, 0) -> scale(0.5f, 1) -> scale(0.7f, 1) -> translate(15, 0)

注意：后调用的pre操作先执行，而后调用的post操作则后执行。

set方法一旦调用即会清空之前matrix中的所有变换，例如：

matrix.preScale(0.5f, 1);
matrix.setScale(1, 0.6f);
matrix.postScale(0.7f, 1);
matrix.preTranslate(15, 0);
等价于

translate(15, 0) -> scale(1, 0.6f) ->  scale(0.7f, 1)

matrix.preScale (0.5f, 1)将不起作用。