位圖 - 獲得非常大的值

我在Android中使用位圖。當我轉換爲灰度時，我應該預期每個像素的值在0到255之間。但對於像素，我將其中的一些作爲0，其他作爲非常大的值。我不知道爲什麼。爲什麼我沒有得到範圍[0,255]的值？我如何得到它？位圖 - 獲得非常大的值

我的代碼是：

//Converting to grayscale 
         int width, height; 
         height = mybitmap.getHeight(); 
         width = mybitmap.getWidth();  

         Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888); 
         Canvas c = new Canvas(bmpGrayscale); 
         Paint paint = new Paint(); 
         ColorMatrix cm = new ColorMatrix(); 
         cm.setSaturation(0); 
         ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm); 
         paint.setColorFilter(f); 
         c.drawBitmap(mybitmap, 0, 0, paint);     
         //Done bmpgrayscale is the grayscale image formed 
         Toast toast23=Toast.makeText(getApplicationContext(),"Grayscale made", Toast.LENGTH_LONG); 
         toast23.show(); 
         for (int i=0;i<210;i++){ 
          for (int j=0;j<170;j++){ 

            Log.d("gray value is=", String.valueOf(bmpGrayscale.getPixel(i, j))); 

          } 
         }

輸出的部分是：

12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 0 
12-07 23:14:28.022: D/gray value is=(958): 83886079 
12-07 23:14:28.022: D/gray value is=(958): 317846001 
12-07 23:14:28.022: D/gray value is=(958): 602992880 
12-07 23:14:28.022: D/gray value is=(958): 669772779 
12-07 23:14:28.022: D/gray value is=(958): 904719596 
12-07 23:14:28.022: D/gray value is=(958): 971894253 
12-07 23:14:28.022: D/gray value is=(958): 1223552493 
12-07 23:14:28.022: D/gray value is=(958): 1223552493 
12-07 23:14:28.022: D/gray value is=(958): 1223552493 
12-07 23:14:28.022: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493 
12-07 23:14:28.052: D/gray value is=(958): 1223552493

請幫助。我正在使用它將我的視圖轉換爲位圖，然後將位圖轉換爲灰度。

編輯

//Converting to grayscale 
         int width, height; 
         height = mybitmap.getHeight(); 
         width = mybitmap.getWidth();  

         Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888); 
         Canvas c = new Canvas(bmpGrayscale); 
         Paint paint = new Paint(); 
         ColorMatrix cm = new ColorMatrix(); 
         cm.setSaturation(0); 
         ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm); 
         paint.setColorFilter(f); 
         c.drawBitmap(mybitmap, 0, 0, paint);     
         //Done bmpgrayscale is the grayscale image formed 
         Toast toast23=Toast.makeText(getApplicationContext(),"Grayscale made", Toast.LENGTH_LONG); 
         toast23.show(); 
         for (int i=0;i<210;i++){ 
          for (int j=0;j<170;j++){ 
            int a=bmpGrayscale.getPixel(i, j); 
            ByteBuffer b = ByteBuffer.allocate(4); 
            //b.order(ByteOrder.BIG_ENDIAN); // optional, the initial order of a byte buffer is always BIG_ENDIAN. 
            b.putInt(a ); 

            byte[] result = b.array();          
            Log.d("gray value is=", String.valueOf((int)result[0])); 

          } 
         }

來源

2012-12-07 Aakash Anuj

我很困惑，爲什麼你的回報expecint 0-255。如果轉換爲十六進制，則較大的值更有意義：83886079 = 4FFFFFFF。 1223552493 = 48EDEDED。注意最後3組字節總是相等的？（灰度值總是RGB相等） – Grambot

@TheCapn好的。但是我希望範圍[0,255]中的值用於進一步的操作。我該怎麼辦？如何將值轉換爲該範圍？ –

將int值轉換爲一系列字節，取最後8個字節並將它們轉換回int？你會得到一個0-255的範圍（0-FF十六進制與0-255十進制相同） – Grambot

不知道爲什麼你得到負值，可能是溢出的事情嗎？這就是我所做的

int value = getLastBytes(1223552493); //Prints 237, the dec value of ED 

public int getLastBytes(long original) { 
String hexBytes = Long.toHexString(original); 
return Integer.parseInt(hexBytes.substring(hexBytes.length()-2),16); 
}

你的情況，你也許可以把它像這樣：

Log.d("gray value is=", getLastBytes(bmpGrayscale.getPixel(i, j)));

來源

2012-12-07 19:07:07 Grambot

位圖 - 獲得非常大的值

回答

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