Android[ how to get RGB values of bitmap in android ]

讀取Bitmap Pixel ARGB (Alpha,red,green,blue),
並且轉換為灰階 (灰階公式: gray = (r*0.299 + g*0.587 + b*0.114))
相較於 bitmap 的 getPixels() 函式快了許多!! 

程式碼：

public static Bitmap toGray(Bitmap src){
        int bmWidth  = src.getWidth();
        int bmHeight = src.getHeight();
        int[] newBitmap = new int[bmWidth * bmHeight];

        src.getPixels(newBitmap, 0, bmWidth, 0, 0, bmWidth, bmHeight);

        for (int h = 0; h < bmHeight; h++){
            for (int w = 0; w < bmWidth; w++){
                int index = h * bmWidth + w;
                int a = (newBitmap[index] >> 24) & 0xff;//讀取Alpha
                int r = (newBitmap[index] >> 16) & 0xff;//讀取red
                int g = (newBitmap[index] >> 8) & 0xff;//讀取green
                int b =  newBitmap[index] & 0xff;//讀取blue
                int gray = (int)(r*0.299 + g*0.587 + b*0.114) ;

                r = gray;
                g = gray;
                b = gray;

                newBitmap[index] = (a << 24) | (r << 16) | (g << 8) | b;
            }
        }

        Bitmap mBmp = Bitmap.createBitmap(bmWidth, bmHeight, Bitmap.Config.ARGB_8888);
        mBmp.setPixels(newBitmap, 0, bmWidth, 0, 0, bmWidth, bmHeight);

        return mBmp;
    }