Android2.3使用BitmapRegionDecoder获取指定区域的图片

最新推荐文章于 2022-10-10 14:40:07 发布

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本文介绍了一个使用触摸事件动态调整ImageView中显示图片区域的Android应用实现方式，通过BitmapRegionDecoder进行图片区域解码，实现了触摸屏上的图片局部放大显示功能。

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public class DisplayImageRegionActivity extends Activity implements OnTouchListener {
  private final Rect mRect = new Rect();
  private BitmapRegionDecoder mDecoder;
  private ImageView mView;

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

mView = new ImageView(this);
mView.setAdjustViewBounds(true);
mView.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
mView.setScaleType(ScaleType.CENTER);
mView.setOnTouchListener(this);
setContentView(mView);

  try {
  InputStream is = getResources().openRawResource(R.drawable.a);
mDecoder = BitmapRegionDecoder.newInstance(is, true);
  } catch (IOException e) {
e.printStackTrace();
  }
  }

@Override
  public boolean onTouch(View v, MotionEvent event) {
  final int action = event.getAction() & MotionEvent.ACTION_MASK;
  final int x = (int) event.getX();
  final int y = (int) event.getY();
  switch (action) {
  case MotionEvent.ACTION_DOWN:
  case MotionEvent.ACTION_MOVE:
setImageRegion(x, y);
  break;
  }
  return true;
  }

  private void setImageRegion(int left, int top) {
// BitmapFactory.Options opts = new BitmapFactory.Options();
  final int width = mView.getWidth();
  final int height = mView.getHeight();

  final int imgWidth = mDecoder.getWidth();
  final int imgHeight = mDecoder.getHeight();

  int right = left + width;
  int bottom = top + height;
  if(right > imgWidth) right = imgWidth;
  if(bottom > imgHeight) bottom = imgHeight;
  if(left < 0) left = 0;
  if(top < 0) top = 0;

mRect.set(left, top, right, bottom);
Bitmap bm = mDecoder.decodeRegion(mRect, null);
mView.setImageBitmap(bm);
  }
}