bitmap 缩放

按比例缩放

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 /**
     * 
     * @param bmp 原 bitmap
     * @param ratio  缩放比例
     * @return
*/
public static Bitmap sizeCompress(Bitmap bmp, int ratio) {
        Bitmap result = Bitmap.createBitmap(bmp.getWidth() / ratio, bmp.getHeight() / ratio, Config.ARGB_8888);
        Canvas canvas = new Canvas(result);
        Rect rect = new Rect(0, 0, bmp.getWidth() / ratio, bmp.getHeight() / ratio);
  
   			Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setAlpha(70); //透明度
       // paint.setColorFilter(new LightingColorFilter(16777215, 13369344));
        canvas.drawBitmap(bmp, (Rect)null, rect, paint);
//        canvas.drawColor(Color.TRANSPARENT);  //设置背景为透明
        return result;
}

指定缩放后大小

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public static Bitmap sizeCompress(Bitmap bmp, int width, int height) {
        int w = bmp.getWidth();
        int h = bmp.getHeight();
        // 定义矩阵对象
        Matrix matrix = new Matrix();
        // 缩放原图
        matrix.postScale((float) width/w, (float) height/h);
        //bmp.getWidth(), bmp.getHeight()分别表示缩放后的位图宽高
        Bitmap result = Bitmap.createBitmap(bmp, 0, 0, w, h, matrix, true);
        return result;
}

drawableToBitmap

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public static Bitmap drawableToBitmap(Drawable drawable) {
  // 取 drawable 的长宽
  int w = drawable.getIntrinsicWidth();
  int h = drawable.getIntrinsicHeight();

  // 取 drawable 的颜色格式
  Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
    : Bitmap.Config.RGB_565;
  // 建立对应 bitmap
  Bitmap bitmap = Bitmap.createBitmap(w, h, config);
  // 建立对应 bitmap 的画布
  Canvas canvas = new Canvas(bitmap);
  drawable.setBounds(0, 0, w, h);
  // 把 drawable 内容画到画布中
  drawable.draw(canvas);
  return bitmap;
}

Drawable缩放

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public static Drawable zoomDrawable(Drawable drawable, int w, int h) {
  int width = drawable.getIntrinsicWidth();
  int height = drawable.getIntrinsicHeight();
  // drawable转换成bitmap
  Bitmap oldbmp = drawableToBitmap(drawable);
  // 创建操作图片用的Matrix对象
  Matrix matrix = new Matrix();
  // 计算缩放比例
  float sx = ((float) w / width);
  float sy = ((float) h / height);
  // 设置缩放比例
  matrix.postScale(sx, sy);
  // 建立新的bitmap，其内容是对原bitmap的缩放后的图
  Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,matrix, true);
  return new BitmapDrawable(newbmp);
}