Thursday, April 25, 2013

[android help] Converting YUV->RGB(Image processing)->YUV during onPreviewFrame in android?


I am capturing image using SurfaceView and getting Yuv Raw preview data in public void onPreviewFrame4(byte[] data, Camera camera)


I have to perform some image preprocessing in onPreviewFrame so i need to convert Yuv preview data to RGB data than image preprocessing and back to Yuv data.


I have used both function for encoding and decoding Yuv data to RGB as following :



public void onPreviewFrame(byte[] data, Camera camera) {
Point cameraResolution = configManager.getCameraResolution();
if (data != null) {
Log.i("DEBUG", "data Not Null");

// Preprocessing
Log.i("DEBUG", "Try For Image Processing");
Camera.Parameters mParameters = camera.getParameters();
Size mSize = mParameters.getPreviewSize();
int mWidth = mSize.width;
int mHeight = mSize.height;
int[] mIntArray = new int[mWidth * mHeight];

// Decode Yuv data to integer array
decodeYUV420SP(mIntArray, data, mWidth, mHeight);

// Converting int mIntArray to Bitmap and
// than image preprocessing
// and back to mIntArray.

// Encode intArray to Yuv data
encodeYUV420SP(data, mIntArray, mWidth, mHeight);
}
}

static public void decodeYUV420SP(int[] rgba, 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);
// rgba, divide 2^10 ( >> 10)
rgba[yp] = ((r << 14) & 0xff000000) | ((g << 6) & 0xff0000)
| ((b >> 2) | 0xff00);
}
}
}


static public void encodeYUV420SP_original(byte[] yuv420sp, int[] rgba,
int width, int height) {
final int frameSize = width * height;

int[] U, V;
U = new int[frameSize];
V = new int[frameSize];

final int uvwidth = width / 2;

int r, g, b, y, u, v;
for (int j = 0; j < height; j++) {
int index = width * j;
for (int i = 0; i < width; i++) {
r = (rgba[index] & 0xff000000) >> 24;
g = (rgba[index] & 0xff0000) >> 16;
b = (rgba[index] & 0xff00) >> 8;

// rgb to yuv
y = (66 * r + 129 * g + 25 * b + 128) >> 8 + 16;
u = (-38 * r - 74 * g + 112 * b + 128) >> 8 + 128;
v = (112 * r - 94 * g - 18 * b + 128) >> 8 + 128;

// clip y
yuv420sp[index++] = (byte) ((y < 0) ? 0 : ((y > 255) ? 255 : y));
U[index] = u;
V[index++] = v;
}
}


The problem is that encoding and decoding Yuv data might have some mistake because if i skip the preprocessing step than also encoded Yuv data are differ from original data of PreviewCallback.


Please help me to resolve this issue. I have to used this code in OCR scanning so i need to implement this type of logic.


If any other way of doing same thing than please provide me.


Thanks in advance. :)



.

stackoverflow.comm

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