public static Bitmap zoomIn(Bitmap bitmap, int maxW, int maxH)

public static Bitmap zoomIn(Bitmap bitmap, int maxW, int maxH) {
   
   int width  = bitmap.getWidth();
   int height = bitmap.getHeight();
   if (width <= maxW && height <= maxH)
    return bitmap;
   Matrix matrix = new Matrix(); // 建立操作圖檔用的Matrix對象
   float ratio = (float) getRatio(width, height, maxW, maxH);
   matrix.postScale(ratio, ratio); // 設定縮放比例
 //  Bitmap oldbmp = drawable.getBitmap(); // drawable轉換成bitmap
   Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true); // 建立新的bitmap，其内容是對原bitmap的縮放後的圖
   return newbmp; // 把bitmap轉換成drawable并傳回
  } 
 
 
private static double getRatio(int srcWidth, int srcHeight, int maxWidth, int maxHeight) {
         double ratio = 0.0;
         double ratio_w = 0.0;
         double ratio_h = 0.0;        // 按比例計算縮放後的圖檔大小，maxLength是長或寬允許的最大長度
         if (srcWidth <= maxWidth && srcHeight <= maxHeight) {
             return 0.0;
         }
         
         ratio_w = (double)maxWidth / (double)srcWidth;
         ratio_h = (double)maxHeight / (double)srcHeight;        if (ratio_w < ratio_h) {
             ratio = ratio_w;
         } else {
             ratio = ratio_h;
         }        return ratio;
     }