I’m creating an Android application that requires me to create a bitmap of the camera preview so that I can average the pixels in the center of the preview, however no matter what the camera is pointed at, the app always returns 0, 0, 0, as the RGB value read from an average of a 9×9 square in the center of the screen. Both preview.java, and the main java file are there. Is this an issue with android (and if so is there a way around it), or is it an issue with my code? Thanks! (sorry if the code is slightly messy)
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.hardware.Camera.ShutterCallback;
import android.os.Bundle;
import android.util.Log;
import android.view.Display;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.FrameLayout;
public class CameraTest2Activity extends Activity {
private static final String TAG = "ZTG";
Camera camera;
Preview preview;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
preview = new Preview(this);
((FrameLayout) findViewById(R.id.preview)).addView(preview);
final Button button = (Button) findViewById(R.id.bFire);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
long timeAtStart = System.currentTimeMillis();
TextView rgbDisplay = (TextView) findViewById(R.id.RGBText);
Display display = getWindowManager().getDefaultDisplay();
int width = display.getWidth();
int height = display.getHeight();
Log.d(TAG, "Width and Height Retrieved As: " + width + ", " + height);
Bitmap b = Bitmap.createBitmap(width, height, Bitmap.Config. RGB_565);
Canvas c = new Canvas(b);
Preview view = (Preview) ((ViewGroup) findViewById(R.id.preview)).getChildAt(0);
view.draw(c);
String hexValue;
int centerX = (display.getWidth() / 2);
int centerY = (display.getHeight() / 2);
int test;
//test = b.getPixel(240, 350);
int sampleWidth = 9;
int sampleHeight = 9;
int[] pixels = new int[sampleWidth * sampleHeight];
b.getPixels(pixels, 0, 9, centerX - 4, centerY - 4, sampleWidth, sampleHeight);
int l = 0;
int tempNum;
int tempBlue;
int tempRed;
int tempGreen;
int blue = 0; //Color.blue(test);
int red = 0; //Color.red(test);
int green = 0; // Color.green(test);
test = 0;
Log.d("lookingFor", "test: " + pixels[1]);
while(l < 81){
tempNum = (Integer) pixels[l];
Log.d("lookingFor", "Pixel Num: " + Color.blue(tempNum));
tempBlue = Color.blue(tempNum);
tempRed = Color.red(tempNum);
tempGreen = Color.green(tempNum);
Log.d("lookingFor", "current Blue: " + tempBlue);
blue = blue + tempBlue;
Log.d("lookingFor", "added blue: " + blue);
red = red + tempRed;
green = green + tempGreen;
l = l + 1; //test g
}
Log.v("lookingFor", blue + " " + red + " " + green);
blue = blue / 81;
red = red / 81;
green = green / 81;
hexValue = Integer.toHexString(test);
Log.d(TAG, "pixel at (" + centerX + ", " + centerY + " succesfully retreived! with value of: " + test);
Log.d(TAG, "and an Hex value of: " + hexValue);
// blue = Color.blue(test);
// red = Color.red(test);
// green = Color.green(test);
//this is a modification
Log.d(TAG, "RGB COLOR! R:" + red + " G:" + green + " B:" + blue);
long timeAtEnd = System.currentTimeMillis();
long totalTime = timeAtEnd - timeAtStart;
Log.d(TAG, "Fetching the color took " + totalTime + " milliseconds");
rgbDisplay.setText("R:" + red + " G:" + green + " B:" + blue);
}
});
Log.d(TAG, "onCreate'd");
}
ShutterCallback shutterCallback = new ShutterCallback() {
public void onShutter() {
Log.d(TAG, "onShutter'd");
}
};
/** Handles data for raw picture */
PictureCallback rawCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
Log.d(TAG, "onPictureTaken - raw");
}
};
/** Handles data for jpeg picture */
PictureCallback jpegCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
FileOutputStream outStream = null;
try {
// write to local sandbox file system
// outStream =
// CameraDemo.this.openFileOutput(String.format("%d.jpg",
// System.currentTimeMillis()), 0);
// Or write to sdcard
outStream = new FileOutputStream(String.format(
"/sdcard/%d.jpg", System.currentTimeMillis()));
outStream.write(data);
outStream.close();
Log.d(TAG, "onPictureTaken - wrote bytes: " + data.length);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
}
Log.d(TAG, "onPictureTaken - jpeg");
}
};
}
(thats the main java file)
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.hardware.Camera;
import android.hardware.Camera.PreviewCallback;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
class Preview extends SurfaceView implements SurfaceHolder.Callback {
private static final String TAG = "Preview";
SurfaceHolder mHolder;
public Camera camera;
Preview(Context context) {
super(context);
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell it where
// to draw.
camera = Camera.open();
try {
camera.setPreviewDisplay(holder);
camera.setPreviewCallback(new PreviewCallback() {
public void onPreviewFrame(byte[] data, Camera arg1) {
/*FileOutputStream outStream = null;
try {
outStream = new FileOutputStream(String.format(
"/sdcard/%d.jpg", System.currentTimeMillis()));
outStream.write(data);
outStream.close();
Log.d(TAG, "onPreviewFrame - wrote bytes: "
+ data.length);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
}*/
Preview.this.invalidate();
}
});
} catch (IOException e) {
e.printStackTrace();
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
// Because the CameraDevice object is not a shared resource, it's very
// important to release it when the activity is paused.
camera.stopPreview();
camera = null;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewSize(w, h);
camera.setParameters(parameters);
camera.startPreview();
}
@Override
public void draw(Canvas canvas) {
super.draw(canvas);
Paint p = new Paint(Color.RED);
Log.d(TAG, "draw");
canvas.drawText("PREVIEW", canvas.getWidth() / 2,
canvas.getHeight() / 2, p);
}
}
Your code averages the pixel values in your new bitmap
bthat you created and not the pixels returned by the camera preview or the camera picture.I think you’ll need to take the byte array passed to onPreviewFrame, convert it from the preview format (most likely YUV422 or YUV420) to your favorite RGB format and then do your math on the RGB colors.