This question has been asked many times already but i cannot seem to find what i want exactly. I am trying to create a camera app where I want to display the YUV or RGB value into the log when I point my camera to some color. The values must me 0...255 range for RGB or correspondent YUV color format. I can manage the conversion between them as there are many such examples on stack overflow. However, i cannot store the values into 3 separate variables and display them in the log.
so far i have managed to get
package com.example.virus.bpreader;
public class CaptureVideo extends SurfaceView implements SurfaceHolder.Callback, Camera.PreviewCallback {
private SurfaceHolder mHolder;
private Camera mCamera;
private int[] pixels;
public CaptureVideo(Context context, Camera cameraManager) {
super(context);
mCamera = cameraManager;
mCamera.setDisplayOrientation(90);
//get holder and set the class as callback
mHolder = getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_NORMAL);
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
//when the surface is created, let the camera start the preview
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
mCamera.cancelAutoFocus();
Camera.Parameters params = mCamera.getParameters();
//get fps
params.getSupportedPreviewFpsRange();
//get resolution
params.getSupportedPreviewSizes();
//stop auto exposure
params.setAutoExposureLock(false);
// Check what resolutions are supported by your camera
List<Camera.Size> sizes = params.getSupportedPictureSizes();
// Iterate through all available resolutions and choose one
for (Camera.Size size : sizes) {
Log.i("Resolution", "Available resolution: " + size.width + " " + size.height);
}
//set resolution at 320*240
params.setPreviewSize(320,240);
//set frame rate at 10 fps
List<int[]> frameRates = params.getSupportedPreviewFpsRange();
int last = frameRates.size() - 1;
params.setPreviewFpsRange(10000, 10000);
//set Image Format
//params.setPreviewFormat(ImageFormat.NV21);
mCamera.setParameters(params);
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
//need to stop the preview and restart on orientation change
if (mHolder.getSurface() == null) {
return;
}
//stop preview
mCamera.stopPreview();
//start again
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
//stop and release
mCamera.startPreview();
mCamera.release();
}
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
int frameHeight = camera.getParameters().getPreviewSize().height;
int frameWidth = camera.getParameters().getPreviewSize().width;
// number of pixels//transforms NV21 pixel data into RGB pixels
int rgb[] = new int[frameWidth * frameHeight];
// convertion
int[] myPixels = decodeYUV420SP(rgb, data, frameWidth, frameHeight);
Log.d("myPixel", String.valueOf(myPixels.length));
}
//yuv decode
int[] decodeYUV420SP(int[] rgb, 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 RGB
rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00) | ((b >> 10) | 0xff);
}
}
return rgb;
}
}
Here the decode method should give a hex format of RGB color space (quite sure its all right as most of the answers are the same). The problem i am facing is when i am not quite sure how to call it inside the OnPreviewFrame method so that it displays the RGB values separately into the log.
N.B like i said i have seen lot of similar questions but could not find a solution to it. I do not want to store the file (image/video) as i only need the RGB/YUV values from the live camera preview when i point the camera to some color.
I need the rgb or yuv values because i want to plot a graph out of it against time.
Any help will be much appreciated.
