Converting YUV->RGB(Image processing)->YUV during onPreviewFrame in android?
https://stackoverflow.com/questions/9325861
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27-10-2019 - |
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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. :)
Solution
Why not specify that camera preview should provide RGB images?
i.e. Camera.Parameters.setPreviewFormat(ImageFormat.RGB_565);
OTHER TIPS
Although the documentation suggests that you can set which format the image data should arrive from the camera in, in practice you often have a choice of one: NV21, a YUV format. For lots of information on this format see http://www.fourcc.org/yuv.php#NV21 and for information on the theory behind converting it to RGB see http://www.fourcc.org/fccyvrgb.php. There is a picture based explanation at Extract black and white image from android camera's NV21 format.
Another format, called YUV420SP, is also quite prevalent.
However, once you've set up your onPreviewFrame routine, the mechanics of going from the byte array it sends you to useful data is somewhat, ummmm, unclear. From API 8 onwards, the following solution is available, to get to a ByteStream holiding a JPEG of the image (compressToJpeg is the only conversion option offered by YuvImage):
// pWidth and pHeight define the size of the preview Frame
ByteArrayOutputStream out = new ByteArrayOutputStream();
// Alter the second parameter of this to the actual format you are receiving
YuvImage yuv = new YuvImage(data, ImageFormat.NV21, pWidth, pHeight, null);
// bWidth and bHeight define the size of the bitmap you wish the fill with the preview image
yuv.compressToJpeg(new Rect(0, 0, bWidth, bHeight), 50, out);
This JPEG may then need to be converted into the format you want. If you want a Bitmap:
byte[] bytes = out.toByteArray();
Bitmap bitmap= BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
If, for whatever reason, you are unable to do this, you can do the conversion manually. Some problems to be overcome in doing this:
The data arrives in a byte array. By definition, bytes are signed numbers, meaning that they go from -128 to 127. However, the data is actually unsigned bytes (0 to 255). If this isn't dealt with, the outcome is doomed to have some odd clipping effects.
The data is in a very specific order (as per the previously mentioned web page) and each pixel needs to be extracted carefully.
Each pixel needs to be put into the right place on a bitmap, say. This also requires a rather messy (in my view) approach of building a buffer of the data and then filling a bitmap from it.
If you've actually got NV12 (or 420SP), then you will need to swap the reads for U and V.
I present a solution (which seems to work), with requests for corrections, improvements and ways of making the whole thing less costly to run. It creates a bitmap the size of the preview image:
The data variable is coming from the call to onPreviewFrame
// the bitmap we want to fill with the image
Bitmap bitmap = Bitmap.createBitmap(imageWidth, imageHeight, Bitmap.Config.ARGB_8888);
int numPixels = imageWidth*imageHeight;
// the buffer we fill up which we then fill the bitmap with
IntBuffer intBuffer = IntBuffer.allocate(imageWidth*imageHeight);
// If you're reusing a buffer, next line imperative to refill from the start,
// if not good practice
intBuffer.position(0);
// Set the alpha for the image: 0 is transparent, 255 fully opaque
final byte alpha = (byte) 255;
// Get each pixel, one at a time
for (int y = 0; y < imageHeight; y++) {
for (int x = 0; x < imageWidth; x++) {
// Get the Y value, stored in the first block of data
// The logical "AND 0xff" is needed to deal with the signed issue
int Y = data[y*imageWidth + x] & 0xff;
// Get U and V values, stored after Y values, one per 2x2 block
// of pixels, interleaved. Prepare them as floats with correct range
// ready for calculation later.
int xby2 = x/2;
int yby2 = y/2;
// make this V for NV12/420SP
float U = (float)(data[numPixels + 2*xby2 + yby2*imageWidth] & 0xff) - 128.0f;
// make this U for NV12/420SP
float V = (float)(data[numPixels + 2*xby2 + 1 + yby2*imageWidth] & 0xff) - 128.0f;
// Do the YUV -> RGB conversion
float Yf = 1.164f*((float)Y) - 16.0f;
int R = (int)(Yf + 1.596f*V);
int G = (int)(Yf - 0.813f*V - 0.391f*U);
int B = (int)(Yf + 2.018f*U);
// Clip rgb values to 0-255
R = R < 0 ? 0 : R > 255 ? 255 : R;
G = G < 0 ? 0 : G > 255 ? 255 : G;
B = B < 0 ? 0 : B > 255 ? 255 : B;
// Put that pixel in the buffer
intBuffer.put(alpha*16777216 + R*65536 + G*256 + B);
}
}
// Get buffer ready to be read
intBuffer.flip();
// Push the pixel information from the buffer onto the bitmap.
bitmap.copyPixelsFromBuffer(intBuffer);
As @Timmmm points out below, you could do the conversion in int by multiplying the scaling factors by 1000 (ie. 1.164 becomes 1164) and then dividng the end results by 1000.
After some tests on Samsung S4 mini fastest code is (120% faster then Neil's [floats!] and 30% faster then original Hitesh's):
static public void decodeYUV420SP(int[] rgba, byte[] yuv420sp, int width,
int height) {
final int frameSize = width * height;
// define variables before loops (+ 20-30% faster algorithm o0`)
int r, g, b, y1192, y, i, uvp, u, v;
for (int j = 0, yp = 0; j < height; j++) {
uvp = frameSize + (j >> 1) * width;
u = 0;
v = 0;
for (i = 0; i < width; i++, yp++) {
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;
}
y1192 = 1192 * y;
r = (y1192 + 1634 * v);
g = (y1192 - 833 * v - 400 * u);
b = (y1192 + 2066 * u);
// Java's functions are faster then 'IFs'
r = Math.max(0, Math.min(r, 262143));
g = Math.max(0, Math.min(g, 262143));
b = Math.max(0, Math.min(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);
}
}
}
Speed is comparable to YuvImage.compressToJpeg() with ByteArrayOutputStream as output (30-50 ms for 640x480 image).
Result: Samsung S4 mini (2x1.7GHz) can't compress to JPEG/convert YUV to RGB in real time (640x480@30fps)
Java implementation is 10 times slow than the c version, I suggest you use GPUImage library or just move this part of code.
There is a android version of GPUImage: https://github.com/CyberAgent/android-gpuimage
You can include this library if you use gradle, and call the method: GPUImageNativeLibrary.YUVtoRBGA( inputArray, WIDTH, HEIGHT, outputArray);
I compare the time, for a NV21 image which is 960x540, use above java code, it cost 200ms+, with GPUImage version, just 10ms~20ms.
You can use RenderScript -> ScriptIntrinsicYuvToRGB
Kotlin Sample
val rs = RenderScript.create(CONTEXT_HERE)
val yuvToRgbIntrinsic = ScriptIntrinsicYuvToRGB.create(rs, Element.U8_4(rs))
val yuvType = Type.Builder(rs, Element.U8(rs)).setX(byteArray.size)
val inData = Allocation.createTyped(rs, yuvType.create(), Allocation.USAGE_SCRIPT)
val rgbaType = Type.Builder(rs, Element.RGBA_8888(rs)).setX(width).setY(height)
val outData = Allocation.createTyped(rs, rgbaType.create(), Allocation.USAGE_SCRIPT)
inData.copyFrom(byteArray)
yuvToRgbIntrinsic.setInput(inData)
yuvToRgbIntrinsic.forEach(outData)
val bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
outData.copyTo(bitmap)
Fixup the above code snippet
static public void decodeYUV420SP(int[] rgba, byte[] yuv420sp, int width,
int height) {
final int frameSize = width * height;
int r, g, b, y1192, y, i, uvp, u, v;
for (int j = 0, yp = 0; j < height; j++) {
uvp = frameSize + (j >> 1) * width;
u = 0;
v = 0;
for (i = 0; i < width; i++, yp++) {
y = (0xff & ((int) yuv420sp[yp])) - 16;
if (y < 0)
y = 0;
if ((i & 1) == 0) {
// above answer is wrong at the following lines. just swap ***u*** and ***v***
u = (0xff & yuv420sp[uvp++]) - 128;
v = (0xff & yuv420sp[uvp++]) - 128;
}
y1192 = 1192 * y;
r = (y1192 + 1634 * v);
g = (y1192 - 833 * v - 400 * u);
b = (y1192 + 2066 * u);
r = Math.max(0, Math.min(r, 262143));
g = Math.max(0, Math.min(g, 262143));
b = Math.max(0, Math.min(b, 262143));
// combine ARGB
rgba[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00)
| ((b >> 10) | 0xff);
}
}
}
Try RenderScript ScriptIntrinsicYuvToRGB, which comes with JellyBean 4.2 (Api 17+).
https://developer.android.com/reference/android/renderscript/ScriptIntrinsicYuvToRGB.html
On Nexus 7 (2013, JellyBean 4.3) a 1920x1080 image conversion (full HD camera preview) takes about 7 ms.
