在检测到的面部上绘制 bitmap，将眼镜对准眼睛

Question

I'm learning face detection on Android using java. I'm doing a tutorial where you draw sunglasses on a detected face. I have the faces and I'm able to draw the bitmap but the sunglasses aren't exactly aligned- they're close. But more specifically where I'm getting held up is the tilting/rotating of the bitmap to match what I'm assuming should be the getHeadEulerAngleY() position from firebase vision faces. I used a Matrix to try and "tilt" the glasses with the Y axis but the glasses only rotate in one direction- so not necessarily the eyes. If it's a float I get from the head Euler Angle Y, wouldn't the negative bitmap rotation corrispond with the value of the float?

I'm also still very knew and trying to learn.

many different answers got me to this point, but now I'm stuck.

For example to aling with the eyes:

 if(leftEye != null && rightEye != null){
          distance = (float) Math.sqrt(
                        Math.pow(rightEye.getPosition().getX() - 
                        leftEye.getPosition().getX(), 2) +
                        Math.pow(rightEye.getPosition().getY() - 
                        leftEye.getPosition().getY(), 2)); 

rect = new Rect(
           Math.round(leftEye.getPosition().getX() - distance), 
           Math.round(leftEye.getPosition().getY() - distance), 
           Math.round(rightEye.getPosition().getX() + distance), 
           Math.round(rightEye.getPosition().getY() + distance));
 }else{
    rect = face.getBoundingBox;
}

this gets the glasses quite closly aligned with eyes.

But what I attempted to do before that code executes was using a Matrix to turn the bitmap first, based on the Y axis:

 Matrix matrix = new Matrix();
    matrix.postRotate(face.getHeadEulerAngleY);

then apply the glasses to the canvas
      canvas.drawBitmap(sunglasses, null, rect, null);
image.setImgBitmap(mutable)

I'm sure I'm missing something. That glasses formula is from a similar function that got me closest to the eyes, so I'm guessing there's a similar one to match the axis. I'm not sure where to start.

Thanks for the help!

Answer 1

I think I got it.... It's crude and SO FAR seems to be working and you cant t tilt too far, but I guess you just want the opposite of the Z and Y axis. As in you're turning the bitmap INTO the axis of the face or whatever. Like a plane yoke.

so-

if(signum(face.Z) < 0) {

matrix.setRotate(Mathabs(faceZ);

}else if(signum(faceZ)>0{

matrix.setRotate(-faceZ);

}else{ setrotate(0) }