Android：將彩色圖像轉換爲灰度

Question

嗨，大家好，我需要你們的幫助，我試圖用紅，綠，藍的平均值將彩色圖像轉換成灰度。但它出來有錯誤，

這裏是我的代碼

imgWidth = myBitmap.getWidth(); 
imgHeight = myBitmap.getHeight(); 

for(int i =0;i<imgWidth;i++) { 
    for(int j=0;j<imgHeight;j++) { 
    int s = myBitmap.getPixel(i, j)/3; 
    myBitmap.setPixel(i, j, s); 
    } 
} 

ImageView img = (ImageView)findViewById(R.id.image1); 
img.setImageBitmap(myBitmap); 

但是當我在模擬器上運行我的應用程序，它是強制關閉。任何想法？

我已經解決了我的問題，使用下面的代碼：

for(int x = 0; x < width; ++x) { 
      for(int y = 0; y < height; ++y) { 
       // get one pixel color 
       pixel = src.getPixel(x, y); 
       // retrieve color of all channels 
       A = Color.alpha(pixel); 
       R = Color.red(pixel); 
       G = Color.green(pixel); 
       B = Color.blue(pixel); 
       // take conversion up to one single value 
       R = G = B = (int)(0.299 * R + 0.587 * G + 0.114 * B); 
       // set new pixel color to output bitmap 
       bmOut.setPixel(x, y, Color.argb(A, R, G, B)); 
      } 
     } 

Answer 1

嘗試解決from this previous answer by leparlon：

public Bitmap toGrayscale(Bitmap bmpOriginal) 
    {   
     int width, height; 
     height = bmpOriginal.getHeight(); 
     width = bmpOriginal.getWidth();  

     Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565); 
     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(bmpOriginal, 0, 0, paint); 
     return bmpGrayscale; 
    } 

Answer 2

拉利特具有最實際的答案。 但是，你想要得到的灰色是平均的紅色，綠色和藍色，並應設置你的矩陣，像這樣：

float oneThird = 1/3f; 
    float[] mat = new float[]{ 
      oneThird, oneThird, oneThird, 0, 0, 
      oneThird, oneThird, oneThird, 0, 0, 
      oneThird, oneThird, oneThird, 0, 0, 
      0, 0, 0, 1, 0,}; 
    ColorMatrixColorFilter filter = new ColorMatrixColorFilter(mat); 
    paint.setColorFilter(filter); 
    c.drawBitmap(original, 0, 0, paint); 

最後，正如我所面對的圖像轉換爲問題灰度前 - 視覺上最令人愉悅的結果在所有情況下由未取平均值，而是通過給予取決於其percieved亮度每個顏色不同的權重來實現，我傾向於使用這些值：

float[] mat = new float[]{ 
      0.3f, 0.59f, 0.11f, 0, 0, 
      0.3f, 0.59f, 0.11f, 0, 0, 
      0.3f, 0.59f, 0.11f, 0, 0, 
      0, 0, 0, 1, 0,}; 

Answer 3

你可以這樣做太：

ColorMatrix matrix = new ColorMatrix(); 
    matrix.setSaturation(0); 

    ColorMatrixColorFilter filter = new ColorMatrixColorFilter(matrix); 
    imageview.setColorFilter(filter);