CODEWITHSUNDEEP
androidcolorsbitmap
Jeungmin Oh
Jeungmin Oh

Reputation: 364

How can I convert android bitmap to NV12 color format?

I'm writing some code for converting android bitmap to NV12 format.

I found code that gives me NV21 from android bitmap, and it seems that the code works. (Convert bitmap array to YUV (YCbCr NV21))

Only difference I found is to switch U and V byte between NV12 and NV21 according to reference. (http://www.fourcc.org/yuv.php)

So I changed the position of U and V from original code, and then the result is like following.

byte [] getNV12(int inputWidth, int inputHeight, Bitmap scaled) {
    // Reference (Variation) : https://gist.github.com/wobbals/5725412

    int [] argb = new int[inputWidth * inputHeight];

    //Log.i(TAG, "scaled : " + scaled);
    scaled.getPixels(argb, 0, inputWidth, 0, 0, inputWidth, inputHeight);

    byte [] yuv = new byte[inputWidth*inputHeight*3/2];
    encodeYUV420SP(yuv, argb, inputWidth, inputHeight);

    scaled.recycle();

    return yuv;
}

void encodeYUV420SP(byte[] yuv420sp, int[] argb, int width, int height) {
    final int frameSize = width * height;

    int yIndex = 0;
    int uvIndex = frameSize;

    int a, R, G, B, Y, U, V;
    int index = 0;
    for (int j = 0; j < height; j++) {
        for (int i = 0; i < width; i++) {

            a = (argb[index] & 0xff000000) >> 24; // a is not used obviously
        R = (argb[index] & 0xff0000) >> 16;
            G = (argb[index] & 0xff00) >> 8;
            B = (argb[index] & 0xff) >> 0;

        // well known RGB to YUV algorithm
        Y = ( (  66 * R + 129 * G +  25 * B + 128) >> 8) +  16;
        V = ( ( -38 * R -  74 * G + 112 * B + 128) >> 8) + 128; // Previously U
        U = ( ( 112 * R -  94 * G -  18 * B + 128) >> 8) + 128; // Previously V

        yuv420sp[yIndex++] = (byte) ((Y < 0) ? 0 : ((Y > 255) ? 255 : Y));
        if (j % 2 == 0 && index % 2 == 0) { 
            yuv420sp[uvIndex++] = (byte)((V<0) ? 0 : ((V > 255) ? 255 : V));
            yuv420sp[uvIndex++] = (byte)((U<0) ? 0 : ((U > 255) ? 255 : U));
        }

        index ++;
        }
    }
}

Am I wrong in converting images? (I'm pretty sure that encoder has no problem.)

Broken image screenshot : https://www.dropbox.com/s/vho14831fgnh1kl/Thu%20Aug%2001%2008_56_14%20GMT%2B09_00%202013%20%281%29.mp4_000002000.jpg

Upvotes: 4

Views: 4995

Answers (3)

Monster Brain
Monster Brain

Reputation: 2119

I was using the same code for creating video using mediaEncoder from camera images. There was an issue of color ( for example images look here) in the generated video. It seems mediaEncoder supports few formats (Ref - Q5)

So had to convert it to N12 (or I420 format), I modified the above code like this based on wikipedia article

int uIndex = frameSize;
int vIndex = frameSize + frameSize/4;

....
     yuv420sp[uIndex++] = (byte)((U<0) ? 0 : ((U > 255) ? 255 : U));
     yuv420sp[vIndex++] = (byte)((V<0) ? 0 : ((V > 255) ? 255 : V));
...

Now the generated video seems to be working fine.

Upvotes: 1

Alexandr
Alexandr

Reputation: 170

you can just use 

R = Color.red(argb[index]);
G = Color.green(argb[index]);
B = Color.blue(argb[index]);

rest of your code works great.

Upvotes: 1

Shashika
Shashika

Reputation: 1161

Replace 

a = (argb[index] & 0xff000000) >> 24; // a is not used obviously
 R = (argb[index] & 0xff0000) >> 16;
 G = (argb[index] & 0xff00) >> 8;
 B = (argb[index] & 0xff) >> 0;

with,

R = (argb[index] & 0xff000000) >>> 24;
G = (argb[index] & 0xff0000) >> 16;
B = (argb[index] & 0xff00) >> 8;

Upvotes: 2

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