Android实现bitmap指定区域滑动截取功能

突然不知道什么心态，说要做这个，网上找了半天没找到合适的，就自己做了一个。

先上效果图：

透明区域为将要截取的区域，其他阴影部位为舍弃区域

图片资源我写死储存在了raw中，有需要可以自己写获取bitmap。

界面layout：

<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>

screenshotview为自定义view用来显示bitmap，以及滑动截图，其中dot类用来储存坐标点的x，y值。

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;
  }

}

mainactivity中完成对点击滑动的监控，通过坐标点的方式获得需要绘制的矩形位置和形状。

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();
  }
}

运用了单例模式用来存储截取出来的bitmap，方便跳转时调用，不需要自己再写类，点击确定后，会将区域中的bitmap提取并存储在单例中，在下一个页面再调用。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。