CODEWITHSUNDEEP
androidarrayscamerargbyuv
LordrAider
LordrAider

Reputation: 65

How to retrieve RGB value for each color apart from one dimensional integer RGB array

I am not too familiar with bit shifting so I have the following question. I use the function below (found elsewhere) to decode from YUV to an RGB int array.

Now I want to adjust red or green or blue values to create some custom filter effect. I need to retrieve the R value, G value, and B value. Each value ranging from 0-255. After that I need to restore it in the rgb array at the specified index. So I need to retrieve each color from rgb[i] and than be able to store it again in rgb[i]

void decodeYUV420SP(int[] rgb, byte[] yuv420sp, int width, int height) {
final int frameSize = width * height;
for (int j = 0, yp = 0; j < height; j++) { 
 int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
 for (int i = 0; i < width; i++, yp++) {
   int y = (0xff & ((int) yuv420sp[yp])) - 16;
   if (y < 0)
   y = 0;
   if ((i & 1) == 0) {
   v = (0xff & yuv420sp[uvp++]) - 128;
   u = (0xff & yuv420sp[uvp++]) - 128;
    }
  int y1192 = 1192 * y;
  int r = (y1192 + 1634 * v);
  int g = (y1192 - 833 * v - 400 * u);
  int b = (y1192 + 2066 * u);
  if (r < 0)
    r = 0;
  else if (r > 262143)
    r = 262143;
  if (g < 0) 
    g = 0;
  else if (g > 262143)
    g = 262143;
  if (b < 0)
    b = 0;
  else if (b > 262143)
    b = 262143;
   rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00) | ((b >> 10) & 0xff);
  }
}
  }
}

Upvotes: 1

Views: 1852

Answers (2)

Konstantin Pribluda
Konstantin Pribluda

Reputation: 12367

Basically color transformation is multiplication of color vector by matrix, and android offers support for it. Look:

http://developer.android.com/reference/android/graphics/ColorMatrix.html

It offers several convenience methods to create desired transformations. ( see sample on end)

How to change colors of a Drawable in Android?

Upvotes: 1

Jave
Jave

Reputation: 31846

For your convenience the Color-class contains many methods for getting and setting specific parts of a 32bit color integer, such as

Color.red(color)

returns the red part of the int color.
Or 

Color.argb(alpha, red, green, blue)

to create an integer from the specified values (range 0-255).
The documentation for the different methods also specifies how to implement the bit-shifting yourself, if that is what you want to do.

Upvotes: 0

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