使用URI從SD卡獲取縮略圖

如何使用給定的URI從SD卡獲取縮略圖？我已經嘗試使用bitmapfactory，但性能不好或OutOfMemoryError 我打算把縮略圖放到有很多數據的列表視圖中我應該使用縮略圖還是使用任何建議？如果要使用縮略圖，那麼該怎麼做......？使用URI從SD卡獲取縮略圖

在此先感謝您的幫助

來源

2012-07-02 Sieryuu

你有沒有試過這種 http://stackoverflow.com/questions/1069095/how-do-you-create-a-thumbnail-image-out-of-a-jpeg在爪哇 – UdayaLakmal

下面的方法可以用來獲取圖像的縮略圖：

private Bitmap getBitmap(String path) { 

    Uri uri = getImageUri(path); 
    InputStream in = null; 
    try { 
     final int IMAGE_MAX_SIZE = 1200000; // 1.2MP 
     in = mContentResolver.openInputStream(uri); 

     // Decode image size 
     BitmapFactory.Options o = new BitmapFactory.Options(); 
     o.inJustDecodeBounds = true; 
     BitmapFactory.decodeStream(in, null, o); 
     in.close(); 



     int scale = 1; 
     while ((o.outWidth * o.outHeight) * (1/Math.pow(scale, 2)) > IMAGE_MAX_SIZE) { 
      scale++; 
     } 
     Log.d(TAG, "scale = " + scale + ", orig-width: " + o.outWidth  + ", orig-height: " + o.outHeight); 

     Bitmap b = null; 
     in = mContentResolver.openInputStream(uri); 
     if (scale > 1) { 
      scale--; 
      // scale to max possible inSampleSize that still yields an image 
      // larger than target 
      o = new BitmapFactory.Options(); 
      o.inSampleSize = scale; 
      b = BitmapFactory.decodeStream(in, null, o); 

      // resize to desired dimensions 
      int height = b.getHeight(); 
      int width = b.getWidth(); 
      Log.d(TAG, "1th scale operation dimenions - width: " + width + ", height: " + height); 

      double y = Math.sqrt(IMAGE_MAX_SIZE 
        /(((double) width)/height)); 
      double x = (y/height) * width; 

      Bitmap scaledBitmap = Bitmap.createScaledBitmap(b, (int) x,  (int) y, true); 
      b.recycle(); 
      b = scaledBitmap; 

      System.gc(); 
     } else { 
      b = BitmapFactory.decodeStream(in); 
     } 
     in.close(); 

     Log.d(TAG, "bitmap size - width: " +b.getWidth() + ", height: " + b.getHeight()); 
     return b; 
    } catch (IOException e) { 
     Log.e(TAG, e.getMessage(),e); 
     return null; 
    } 
}

而且總是使用位圖後調用bitmap.recycle（）方法。它會清除內存中的位圖。還要避免代碼中的內存泄漏。這將解決你的OOME。

來源

2012-07-02 08:48:53 Shrikant

的編碼工作，但滾動並不那麼順利，即使有我的列表視圖上的10個項目。我已將IMAGE MAX SIZE設置爲100，但仍未解決性能問題。哦，我在我的自定義適配器上使用回收，並得到了'運行時異常：試圖使用回收位圖的畫布' – Sieryuu

在回收它之前檢查（位圖！= null）。你使用哪個Android版本？如果它的3.0及以上版本在xml中爲listView提供hardwareAccelerated = true – Shrikant

// Parameters 
int w,h;  

// First only decode image size 
BitmapFactory.Options opt = new BitmapFactory.Options(); 
opt.inJustDecodeBounds = true; 
Bitmap bmp = BitmapFactory.decodeFile(file, opt); 

// Decode small enough image 
int heightRatio = (int)opt.outHeight/h; 
int widthRatio = (int)opt.outWidth/w; 
if (heightRatio > 1 || widthRatio > 1) 
{ 
     if (heightRatio > widthRatio) 
      opt.inSampleSize = heightRatio; 
     else 
      opt.inSampleSize = widthRatio; 
} 

opt.inJustDecodeBounds = false; 
bmp = BitmapFactory.decodeFile(file, opt);

來源

2012-07-02 08:45:51 ssteinberg

感謝您的回答，順便說一句我已經嘗試過你的編碼負載比我以前的代碼更快，但滾動的列表視圖不光滑。 – Sieryuu

使用ThumbnailUtils類來獲取圖像/視頻的拇指。

來源

2012-07-02 08:46:07

好的，我會嘗試使用那個類。 – Sieryuu

試一試這段代碼，它修復了內存不足錯誤。改變你的高度和寬度。這裏intent_data2是文件路徑。

public Bitmap custom_SizedImage(String intent_data2) { 
     int targetHeight = 534, targetWidth = 534; 
     Options options = new Options(); 
     options.inJustDecodeBounds = true; 
     BitmapFactory.decodeFile(intent_data2, options); 
     double sampleSize = 0; 
     Boolean scaleByHeight = Math.abs(options.outHeight - targetHeight) >= Math 
       .abs(options.outWidth - targetWidth); 

     if (options.outHeight * options.outWidth * 2 >= 1638) { 
      sampleSize = scaleByHeight ? options.outHeight/targetHeight 
        : options.outWidth/targetWidth; 
      sampleSize = (int) Math.pow(2d, 
        Math.floor(Math.log(sampleSize)/Math.log(2d))); 
     } 
     options.inJustDecodeBounds = false; 
     options.inTempStorage = new byte[128]; 
     while (true) { 
      try { 
       options.inSampleSize = (int) sampleSize; 
       mBitmap = BitmapFactory.decodeFile(intent_data2, options); 
       Display display = getWindowManager().getDefaultDisplay(); 
       int width = display.getWidth(); 
       int height = display.getHeight(); 
       int screenDiff = height - width; 
       int screenRatio = screenDiff/3; 
       float scaleFactor = mBitmap.getWidth()/width; 
       float y_Pos = scaleFactor * screenRatio; 
       Matrix matrix = new Matrix(); 
       matrix.postScale(0.5f, 0.5f); 
       croppedBitmap = Bitmap.createBitmap(mBitmap, 0, (int) y_Pos, 
         mBitmap.getWidth(), mBitmap.getWidth(), matrix, true); 

       scaledBitmap = Bitmap.createBitmap(targetWidth, targetHeight, 
         Config.RGB_565); 

       float ratioX = targetWidth/(float) croppedBitmap.getWidth(); 
       float ratioY = targetHeight/(float) croppedBitmap.getHeight(); 
       float middleX = targetWidth/2.0f; 
       float middleY = targetHeight/2.0f; 

       Matrix scaleMatrix = new Matrix(); 
       scaleMatrix.setScale(ratioX, ratioY, middleX, middleY); 

       Canvas canvas = new Canvas(scaledBitmap); 
       canvas.setMatrix(scaleMatrix); 
       canvas.drawBitmap(croppedBitmap, 
         middleX - croppedBitmap.getWidth()/2, middleY 
           - croppedBitmap.getHeight()/2, new Paint(
           Paint.FILTER_BITMAP_FLAG)); 
       //saveImage(scaledBitmap); 

       break; 
      } catch (Exception ex) { 
       try { 
        sampleSize = sampleSize * 2; 
       } catch (Exception ex1) { 

       } 
      } 
     } 
     return scaledBitmap;

}

來源

2012-07-02 08:49:34 Aerrow

什麼是saveimage（）方法？ – Sieryuu

如果你想保存圖像意味着使用該方法，否則評論它。 – Aerrow

使用URI從SD卡獲取縮略圖

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