自己計算的RGB值與實際的RGB值不匹配

我正在研究一個程序，在該程序中，我獲取圖像的一部分並計算該圖像的平均RGB值。當我計算它時，我會得到完全不同的值，就像我使用內置函數一樣。當我測試我的數字並將它們放入RGB彩色圖表時，它們關閉，而內置函數非常準確。使用內置函數的問題在於它幾乎沒有功能。它只是打印出我的計算結果，但我無法使用這些數據。 link to function called dump()自己計算的RGB值與實際的RGB值不匹配

public void readSquares(Mat img){ 

    int width = 20; 
    int height = 20; 
    int rSum = 0; 
    int gSum = 0; 
    int bSum = 0; 
    int rAvg = 0; 
    int gAvg = 0; 
    int bAvg = 0; 

    Imgproc.cvtColor(img, img, Imgproc.COLOR_BGR2RGB); 
    int channels = img.channels(); 

    int totalBytes = (int)(img.total() * img.channels()); 

    byte buff[] = new byte[totalBytes]; 
    img.get(0, 0, buff); 

    for (int i=0; i< height; i++) { 
     //stride is the number of bytes in a row of smallImg 
     int stride = channels * width; 
     for (int j=0; j<stride; j+=channels) { 
      int r = buff[(i * stride) + j]; 
      int g = buff[(i * stride) + j + 1]; 
      int b = buff[(i * stride) + j + 2]; 

      if(r < 0 || g < 0 || b < 0){ 
       r = Math.abs(r); 
       g = Math.abs(g); 
       b = Math.abs(b);  
      } 

      rSum += r; 
      gSum += g; 
      bSum += b; 

     } 
    } 

    rAvg = (int) (rSum/img.total()); //total pixels in picture 
    gAvg = (int) (gSum/img.total()); 
    bAvg = (int) (bSum/img.total()); 
    System.out.println("R: " + rAvg); 
    System.out.println("G: " + gAvg); 
    System.out.println("B: " + bAvg);

下面這打印出精確的值，但我不能單獨通道或發現平均RGB它只是吐出所有的東西作爲我不能使用的字符串。

System.out.println(img.dump()); 
}

這裏是一個例子;我讀像素紅色圖像，這是輸出：

我的計算值

R:18 
G:27 
B:64

功能第一個數字代表將R的第二G和第三B.它確實，對於每一個像素在圖像中。

[237, 24, 60, 236, 23, 59, 236, 26, 56, 234, 25, 55, 238, 27, 62, 238, 27, 62, 238, 27, 62, 236, 25, 60, 234, 24, 59, 233, 23, 57, 234, 24, 59, 234, 24, 59, 235, 22, 59, 235, 22, 59, 237, 21, 59, 235, 20, 58, 237, 19, 56, 237, 19, 56, 239, 19, 52, 237, 18, 51; 
236, 24, 55, 237, 25, 56, 237, 25, 54, 237, 25, 54, 236, 26, 56, 237, 27, 57, 238, 28, 58, 239, 29, 59, 238, 27, 62, 234, 24, 59, 237, 24, 62, 237, 24, 62, 238, 22, 63, 237, 20, 61, 235, 20, 58, 235, 20, 58, 237, 19, 58, 239, 21, 61, 237, 19, 56, 236, 18, 55; 
238, 26, 57, 238, 26, 57, 234, 25, 53, 232, 23, 50, 236, 26, 54, 237, 27, 55, 237, 27, 55, 237, 27, 55, 237, 26, 61, 236, 25, 60, 237, 24, 62, 237, 24, 62, 238, 22, 63, 237, 20, 61, 238, 22, 63, 238, 22, 63, 238, 20, 61, 238, 20, 61, 237, 19, 56, 236, 18, 55; 
242, 30, 60, 240, 27, 58, 235, 24, 49, 233, 21, 47, 234, 22, 48, 237, 26, 52, 236, 25, 50, 237, 26, 52, 238, 26, 57, 237, 25, 56, 239, 23, 62, 239, 23, 62, 238, 22, 63, 238, 22, 63, 238, 19, 63, 239, 20, 65, 238, 20, 61, 239, 21, 63, 238, 20, 59, 236, 18, 57; 
240, 27, 62, 236, 23, 59, 236, 24, 53, 236, 24, 53, 235, 23, 51, 234, 22, 50, 235, 23, 51, 236, 24, 53, 237, 24, 60, 236, 23, 59, 237, 24, 64, 237, 24, 64, 237, 24, 64, 236, 22, 63, 238, 22, 63, 238, 22, 63, 237, 20, 61, 237, 20, 61, 237, 21, 59, 235, 20, 58; 
238, 25, 61, 237, 24, 60, 237, 24, 60, 237, 24, 60, 235, 22, 57, 236, 23, 59, 235, 22, 57, 235, 22, 57, 234, 21, 56, 236, 23, 59, 237, 24, 62, 236, 23, 61, 237, 20, 61, 237, 20, 61, 238, 21, 65, 238, 21, 65, 238, 22, 63, 237, 20, 61, 235, 22, 59, 235, 22, 59; 
238, 27, 62, 237, 26, 61, 237, 24, 60, 236, 23, 59, 236, 24, 55, 236, 24, 55, 236, 24, 55, 234, 22, 52, 237, 22, 53, 237, 22, 53, 237, 21, 57, 237, 21, 57, 237, 21, 59, 237, 21, 59, 237, 20, 61, 237, 20, 61, 236, 22, 63, 236, 22, 63, 236, 22, 63, 235, 21, 61; 
237, 26, 63, 236, 25, 62, 237, 24, 62, 237, 24, 62, 238, 25, 63, 237, 24, 62, 237, 21, 57, 238, 22, 59, 237, 21, 57, 237, 21, 57, 235, 20, 56, 235, 20, 56, 235, 20, 56, 237, 21, 57, 237, 21, 57, 238, 22, 59, 235, 23, 53, 236, 24, 55, 236, 24, 53, 236, 24, 53; 
236, 29, 69, 235, 28, 68, 238, 26, 70, 239, 27, 71, 240, 25, 68, 238, 24, 67, 237, 24, 64, 236, 22, 63, 237, 20, 61, 235, 19, 60, 237, 19, 58, 236, 18, 57, 237, 21, 59, 237, 21, 59, 238, 22, 59, 240, 25, 61, 237, 25, 56, 236, 24, 55, 236, 24, 53, 237, 25, 54; 
235, 28, 66, 235, 28, 66, 237, 25, 65, 240, 29, 68, 241, 27, 67, 238, 25, 65, 239, 23, 64, 238, 22, 63, 237, 19, 58, 237, 19, 58, 237, 17, 57, 237, 17, 57, 240, 20, 57, 241, 21, 59, 238, 21, 53, 239, 22, 55, 240, 26, 55, 238, 23, 53, 237, 22, 51, 237, 22, 51; 
237, 25, 69, 237, 25, 69, 239, 27, 73, 239, 27, 73, 240, 25, 70, 241, 26, 71, 239, 22, 66, 237, 20, 63, 238, 20, 61, 237, 18, 60, 236, 17, 59, 237, 18, 60, 238, 20, 59, 239, 21, 61, 238, 22, 59, 238, 22, 59, 239, 25, 54, 237, 22, 51, 237, 23, 49, 235, 22, 48; 
237, 25, 65, 238, 27, 66, 238, 27, 66, 238, 27, 66, 238, 27, 66, 237, 25, 65, 236, 22, 63, 235, 21, 61, 235, 22, 59, 235, 22, 59, 234, 18, 57, 237, 21, 59, 238, 22, 61, 238, 22, 61, 238, 22, 59, 238, 22, 59, 238, 20, 57, 238, 20, 57, 237, 20, 52, 237, 20, 52; 
236, 25, 60, 236, 25, 60, 238, 27, 62, 239, 29, 63, 237, 26, 61, 236, 25, 60, 237, 26, 61, 236, 25, 60, 236, 23, 59, 235, 22, 57, 236, 23, 59, 235, 22, 57, 237, 24, 60, 236, 23, 59, 238, 22, 59, 237, 21, 57, 237, 21, 57, 235, 20, 56, 236, 18, 55, 235, 17, 54; 
237, 25, 56, 238, 26, 57, 237, 27, 57, 237, 27, 57, 236, 26, 56, 237, 27, 57, 238, 28, 58, 237, 27, 57, 237, 27, 57, 238, 28, 58, 240, 27, 58, 237, 25, 56, 236, 23, 59, 236, 23, 59, 237, 21, 57, 237, 21, 57, 235, 20, 58, 235, 20, 58, 236, 18, 55, 236, 18, 55; 
237, 25, 54, 237, 25, 54, 237, 25, 54, 235, 23, 51, 237, 25, 56, 240, 27, 58, 237, 26, 61, 236, 25, 60, 237, 26, 63, 237, 26, 63, 238, 27, 66, 236, 24, 64, 237, 24, 64, 236, 22, 63, 237, 20, 61, 235, 19, 60, 236, 17, 59, 236, 17, 59, 236, 18, 57, 235, 16, 56; 
237, 25, 56, 237, 25, 56, 236, 23, 59, 238, 25, 61, 237, 24, 62, 238, 25, 63, 237, 24, 64, 238, 25, 65, 240, 25, 68, 238, 24, 67, 237, 23, 66, 237, 23, 66, 238, 21, 65, 238, 21, 65, 237, 20, 63, 237, 20, 63, 235, 19, 62, 235, 19, 62, 235, 19, 60, 235, 19, 60; 
237, 25, 56, 237, 25, 56, 237, 24, 60, 237, 24, 60, 237, 24, 64, 234, 20, 60, 237, 23, 66, 238, 24, 67, 238, 24, 69, 237, 23, 68, 236, 23, 70, 234, 22, 69, 236, 22, 67, 233, 18, 63, 236, 22, 65, 235, 21, 63, 236, 22, 63, 234, 20, 60, 235, 22, 59, 235, 22, 59; 
238, 27, 55, 238, 27, 55, 239, 24, 56, 241, 27, 58, 237, 24, 62, 237, 24, 62, 237, 23, 66, 238, 24, 67, 237, 24, 71, 237, 24, 71, 236, 23, 72, 234, 22, 71, 231, 19, 65, 236, 23, 70, 236, 24, 68, 236, 24, 68, 237, 24, 62, 236, 23, 61, 236, 24, 55, 238, 26, 57; 
239, 29, 63, 236, 25, 60, 236, 25, 62, 236, 25, 62, 236, 24, 64, 237, 25, 65, 234, 27, 67, 232, 26, 66, 238, 31, 74, 236, 29, 71, 234, 26, 71, 231, 24, 69, 232, 25, 70, 234, 26, 71, 236, 29, 71, 238, 31, 74, 235, 28, 68, 232, 26, 66, 237, 26, 63, 236, 25, 62; 
237, 24, 60, 237, 24, 60, 237, 26, 61, 236, 25, 60, 233, 22, 59, 234, 24, 61, 232, 26, 62, 234, 28, 63, 234, 27, 65, 234, 27, 65, 234, 26, 69, 234, 26, 69, 234, 26, 73, 234, 26, 73, 237, 29, 79, 238, 30, 80, 236, 29, 71, 234, 26, 69, 237, 26, 63, 238, 27, 64]

來源

2017-04-03 cuber

這些值是正確的。你沒有意識到的是你正在使用帶符號的字節，這意味着所有高於127的紅色值都是負值。 240變成-15等。然後你採取絕對和平均的。這可能不是你想要的。轉換爲無符號和平均值。一個簡單的調試會話會立即告訴你這些值發生了什麼。 –

我如何將它們轉換爲無符號字節？ @SamiKuhmonen – cuber

我會對我的轉換做些什麼？ @SamiKuhmonen – cuber

嚴格地說，Java語言規範指出，一個字節的數據類型-128的範圍 - 127，這就是Java將如何解釋一個字節。例如，如果一個字節被提升或轉換爲int，則Java會將第一位解釋爲符號並使用符號擴展。沒有語言支持來幫助您以不同的方式解釋一個字節。（例如，在Java中沒有無符號關鍵字。）

即使這樣，沒有任何東西阻止您將字節視爲8位值，並將這些位解釋爲無符號。只要記住，你無法做出任何事情來迫使你對別人的方法進行解釋。如果一個方法接受一個字節，那麼該方法接受一個介於-128和127之間的值，除非另有明確說明。

public static int unsignedToBytes(byte b) { 
     return b & 0xFF; 
    }

這種方法做你所問。希望這可以幫助！！！

編輯：Stack Overflow和其他地方有很多很好的答案。我建議您在發佈問題前嘗試找到答案。謝謝。

來源

2017-04-03 05:00:26

我想出了謝謝你的幫助:) – cuber

沒問題，很高興幫助。 –

自己計算的RGB值與實際的RGB值不匹配

回答

相關問題