Android实现bitmap指定区域滑动截取功能

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context="com.admin.myapplication.MainActivity" 
  <com.admin.myapplication.ScreenShotView
    android:id="@+id/screenShotView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/ 
  <LinearLayout
    android:id="@+id/title"
    android:layout_width="match_parent"
    android:layout_height="30dp"
    android:background="#000000" 
    <TextView
      android:layout_width="match_parent"
      android:layout_height="20dp"
      android:layout_gravity="center"
      android:gravity="center"
      android:text="选择要截取区域"/ 
  </LinearLayout 
  <LinearLayout
    android:id="@+id/bottom"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    android:layout_alignParentBottom="true"
    android:background="#000000"
    android:orientation="horizontal" 
    <TextView
      android:id="@+id/cancel_btn"
      android:text="取消"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:layout_weight="1"
      android:layout_gravity="center_vertical"
      android:gravity="center"/ 
    <TextView
      android:id="@+id/certain_btn"
      android:text="确定"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:layout_weight="1"
      android:layout_gravity="center_vertical"
      android:gravity="center"/ 
    <TextView
      android:id="@+id/restart_btn"
      android:text="重试"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:layout_weight="1"
      android:layout_gravity="center_vertical"
      android:gravity="center"/ 
  </LinearLayout 

</RelativeLayout 

public class ScreenShotView extends View {
private Dot startDot;
private Dot endDot;
private Bitmap mBitmap;
private Bitmap ocrBitmap;
private int screenHeight;
private int screenWidth;
private Dot leftTopDot;
private Dot rightBottomDot;
private Paint paintShadow;
int shadow = 0xaa000000;
int clear = 0x0000000;
public ScreenShotView(Context context) {
super(context);
startDot = new Dot();
endDot = new Dot();
leftTopDot = new Dot();
rightBottomDot = new Dot();
}
public ScreenShotView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
startDot = new Dot();
endDot = new Dot();
leftTopDot = new Dot();
rightBottomDot = new Dot();
}
public ScreenShotView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
startDot = new Dot();
endDot = new Dot();
leftTopDot = new Dot();
rightBottomDot = new Dot();
}
public void setBitmap(Bitmap bitmap, int screenHeight, int screenWidth) {
mBitmap = bitmap;
this.screenHeight = screenHeight;
this.screenWidth = screenWidth;
changeBitmapSize();
invalidate();
}
public void restart(){
startDot = new Dot();
endDot = new Dot();
leftTopDot = new Dot();
rightBottomDot = new Dot();
invalidate();
}
/**
*将将要显示的bitmap进行变形，使其铺满屏幕
*
*/
private void changeBitmapSize() {
int width = mBitmap.getWidth();
int height = mBitmap.getHeight();
float scaleWidth = ((float) screenWidth) / width;
float scaleHeight = ((float) screenHeight) / height;
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
mBitmap = Bitmap.createBitmap(mBitmap, 0, 0, width, height, matrix, true);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
getLeftTopDot();
getRightBottomDot();
drawBitmap(canvas);
drawArea(canvas);
drawShadowTop(canvas);
drawShadowLeft(canvas);
drawShadowRight(canvas);
drawShadowBottom(canvas);
}
/**
*绘制阴影
*
*/
private void drawShadowBottom(Canvas canvas) {
paintShadow = new Paint();
paintShadow.setColor(shadow);
canvas.drawRect(0, rightBottomDot.getY(), screenWidth, screenHeight, paintShadow);
}
private void drawShadowRight(Canvas canvas) {
paintShadow = new Paint();
paintShadow.setColor(shadow);
canvas.drawRect(rightBottomDot.getX(), leftTopDot.getY(), screenWidth, rightBottomDot.getY(), paintShadow);
}
private void drawShadowLeft(Canvas canvas) {
paintShadow = new Paint();
paintShadow.setColor(shadow);
canvas.drawRect(0, leftTopDot.getY(), leftTopDot.getX(), rightBottomDot.getY(), paintShadow);
}
private void drawShadowTop(Canvas canvas) {
paintShadow = new Paint();
paintShadow.setColor(shadow);
canvas.drawRect(0, 0, screenWidth, leftTopDot.getY(), paintShadow);
}
private void drawBitmap(Canvas canvas) {
Paint paint = new Paint();
canvas.drawBitmap(mBitmap, 0, 0, paint);
}
/**
* 画出截图区域
*
* @param canvas
*/
private void drawArea(Canvas canvas) {
Paint paint = new Paint();
paint.setColor(clear);
canvas.drawRect(leftTopDot.getX(), leftTopDot.getY(), rightBottomDot.getX(), rightBottomDot.getY(), paint);
}
/**
* 获取截图区域bitmap
*
* @return 截图
*/
public Bitmap getBitmap() {
if (mBitmap != null) {
getLeftTopDot();
getRightBottomDot();
if (getBitmapOutWidth()   0 && getBitmapOutHeight()   0) {
if(leftTopDot.getY()<0){
leftTopDot.setY(0);
}
ocrBitmap = Bitmap.createBitmap(mBitmap, (int) leftTopDot.getX(), (int) leftTopDot.getY(), getBitmapOutWidth(), getBitmapOutHeight());
}
}
return ocrBitmap;
}
/**
* 获取截图区域宽度
*
* @return
*/
private int getOutWidth() {
return (int) (rightBottomDot.getX() - leftTopDot.getX());
}
/**
* 获取截图区域高度
*
* @return
*/
private int getOutHeight() {
return (int) (rightBottomDot.getY() - leftTopDot.getY());
}
private int getBitmapOutWidth() {
int bitmapOutWidth;
int scale = getOutWidth() * mBitmap.getWidth();
bitmapOutWidth = scale / screenWidth;
return bitmapOutWidth;
}
private int getBitmapOutHeight() {
int bitmapOutHeight;
int scale = getOutHeight() * mBitmap.getHeight();
bitmapOutHeight = scale / screenHeight;
return bitmapOutHeight;
}
private void getLeftTopDot() {
if (endDot.getX()   startDot.getX()) {
leftTopDot.setX(startDot.getX());
} else {
leftTopDot.setX(endDot.getX());
}
if (endDot.getY()   startDot.getY()) {
leftTopDot.setY(startDot.getY());
} else {
leftTopDot.setY(endDot.getY());
}
}
private void getRightBottomDot() {
if (startDot.getX()   endDot.getX()) {
rightBottomDot.setX(startDot.getX());
} else {
rightBottomDot.setX(endDot.getX());
}
if (startDot.getY()   endDot.getY()) {
rightBottomDot.setY(startDot.getY());
} else {
rightBottomDot.setY(endDot.getY());
}
}
public Dot getStartDot() {
return startDot;
}
public void setStartDot(Dot startDot) {
this.startDot = startDot;
}
public Dot getEndDot() {
return endDot;
}
public void setEndDot(Dot endDot) {
this.endDot = endDot;
}
}

public class MainActivity extends AppCompatActivity implements View.OnTouchListener, View.OnClickListener {
private ScreenShotView screenShotView;
private Bitmap bmp;
private Bitmap ocrBitmap;
private TextView certainBtn;
private TextView cancelBtn;
private TextView restartBtn;
private int screenWidth;
private int screenHeight;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
screenShotView = (ScreenShotView) findViewById(R.id.screenShotView);
cancelBtn = (TextView) findViewById(R.id.cancel_btn);
cancelBtn.setOnClickListener(this);
certainBtn = (TextView) findViewById(R.id.certain_btn);
certainBtn.setOnClickListener(this);
restartBtn = (TextView)findViewById(R.id.restart_btn);
restartBtn.setOnClickListener(this);
DisplayMetrics dm = new DisplayMetrics();
//获取屏幕信息
getWindowManager().getDefaultDisplay().getMetrics(dm);
screenWidth = dm.widthPixels;
screenHeight = dm.heightPixels;
Resources r = this.getResources();
InputStream is = r.openRawResource(R.raw.bg);
BitmapDrawable bmpDraw = new BitmapDrawable(is);
bmp = bmpDraw.getBitmap();
screenShotView.setBitmap(bmp, screenHeight, screenWidth);
screenShotView.setOnTouchListener(this);
}
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
switch (motionEvent.getAction()) {
case MotionEvent.ACTION_DOWN:
screenShotView.setStartDot(new Dot(motionEvent.getX(), motionEvent.getY()));
break;
case MotionEvent.ACTION_MOVE:
screenShotView.setEndDot(new Dot(motionEvent.getX(), motionEvent.getY()));
screenShotView.setBitmap(bmp, screenHeight, screenWidth);
break;
case MotionEvent.ACTION_UP:
ocrBitmap = screenShotView.getBitmap();
break;
}
return true;
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.cancel_btn:
finish();
break;
case R.id.certain_btn:
if (ocrBitmap != null) {
BitmapUtil.getInstance().setImageBitmap(ocrBitmap);
Intent intent = new Intent(MainActivity.this, Main2Activity.class);
startActivity(intent);
}else{
Toast.makeText(MainActivity.this,"请选择截取区域",Toast.LENGTH_SHORT).show();
}
break;
case R.id.restart_btn:
screenShotView.restart();
break;
}
}
@Override
protected void onResume() {
super.onResume();
screenShotView.restart();
}
@Override
protected void onRestart() {
super.onRestart();
screenShotView.restart();
}
}