Android 圖片加載相關問題

1、Android 圖片加載過大導致內存溢出解決辦法

public void loadImage(){
  //取得手機窗體的寬高
  WindowManager wm = this.getWind

owManager();
  int screenWidth = wm.getDefaultDisplay().getWidth();
  int screenHeight = wm.getDefaultDisplay().getHeight();

  //通過圖片文件的信息，得到圖片的寬高
  BitmapFactory.Options options = new Options();//解析位圖附加條件
  options.inJustDecodeBounds = true;  //不去解析圖像，只得到圖像的文件信息
  Bitmap bitmap = BitmapFactory.decodeFile("File path",options);

  //得到圖片寬高
  int imageWidth = options.outWidth;
  int imageHeight = options.outHeight;

  //計算縮放比
  int scaleWidth = imageWidth / screenWidth;
  int scaleHeight = imageHeight / screenHeight;

  //取得合適縮放比
  int scale = 1;
  if(scaleWidth > scaleHeight && scaleHeight > 1){
   scale = scaleWidth;
  }
  if(scaleHeight > scaleWidth && scaleWidth > 1){
   scale = scaleHeight;
  }

  //加載真是圖片
  options.inSampleSize = scale;
  options.inJustDecodeBounds = false;
  bitmap = BitmapFactory.decodeFile("File Path", options);

  //將圖片顯示在你要顯示的控件上
  //建議使用WeakReference代替強引用
 }

2.拷貝圖片

public void copyImage(){
  //導入位圖
  Bitmap bitmap = BitmapFactory.decodeResource(this.getResources(),R.drawable.ic_lock_idle_alarm);
  //創建一個圖形的副本，此時的這個副本是空白的
  Bitmap alterBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(),     bitmap.getConfig());
  //準備一個畫板，在上面放上準備好的空白的位圖
  Canvas canvas = new Canvas();
  //準備一個畫筆
  Paint paint = new Paint();
  paint.setColor(Color.WHITE);

  //畫圖
  Matrix m = new Matrix();
  canvas.drawBitmap(bitmap,m,paint);

 }

3、圖形的縮放

//圖形縮放函數（行列式）
Matrix matrix = new Matrix();
matrix.setValues(new float[] {
  1, 0, 0,
  0, 1, 0,
  0, 0, 1
});
x = 1x + 0y + 0z
y = 0x + 1y + 0z
z = 0x + 0y + 1z

通過canvas.drawBitmap(bmp, matrix, paint);
創建bitmap；
(1)水平縮放0.5
(2)垂直拉扯2倍

matrix.setScale(1.5f,1);//水平點放大到1.5f,垂直1

4、圖形的旋轉

Matrix matrix = new Matrix();
matrix.setRotate(15);
canvas.drawBitmap(bmp, matrix, paint);

5、消除鋸齒

paint.setAntiAlias(true);  

6、指定圓心的旋轉

matrix.setRotate(15,bmp.getWidth()/2,bmp.getHeight()/2);
Matrix matrix = new Matrix();
matrix.setRotate(15,bmp.getWidth()/2,bmp.getHeight()/2);
alteredBitmap = Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(), bmp.getHeight(),
matrix, false);
alteredImageView.setImageBitmap(alteredBitmap);