Make video fill screen and keep aspect ratio

问题:

Java and C# (Xamarin.Android) accepted

• I have a MediaRecorder that streams the cameraframes onto a TextureView (basic camera2 approach)
• the TextureView fills my screen.

I want the video to fill the screen but keep the aspect ratio.

I know I have to eventually cut of either left/right or top/bottom parts of the video, to keep the aspect ratio.

How can I make the video fit the TextureView and "zoom in" until the whole screen is filled? I don't want "black bars" that compromise for the ratio to be kept.

I guess this has to be accomplished through overriding the OnMeasure of the TextureView

C# extended TextureView

//Called by my MediaRecorder Implementation, when I set the video dimensions (mostly width = 1280, height = 720)
public void SetAspectRatio(int width, int height)
        {
            if (width == 0 || height == 0)
                throw new ArgumentException("Size cannot be negative.");
            mRatioWidth = width;
            mRatioHeight = height;
            RequestLayout();
        }

        protected override void OnMeasure(int widthMeasureSpec, int heightMeasureSpec)
        {
            base.OnMeasure(widthMeasureSpec, heightMeasureSpec);
            int width = MeasureSpec.GetSize(widthMeasureSpec);
            int height = MeasureSpec.GetSize(heightMeasureSpec);
            if (0 == mRatioWidth || 0 == mRatioHeight)
            {
                SetMeasuredDimension(width, height);
            }
            else
            {
                if (width > (float)height * mRatioWidth / (float)mRatioHeight)
                {
                    SetMeasuredDimension(width, width * mRatioHeight / mRatioWidth);
                }
                else
                {
                    SetMeasuredDimension(height * mRatioWidth / mRatioHeight, height);
                }
            }
        }

回答1:

I have found the answer, thanks to this comment from this post.

C# Xamarin.Android:

I call the following method when my surface texture size changes (OnSurfaceSizeTextureChanged callback in SurfaceTextureListener)

public void ConfigureTransform(int viewWidth, int viewHeight)
{
    int rotation = (int)ThisActivity.WindowManager.DefaultDisplay.Rotation;
    var matrix = new Matrix();
    var viewRect = new RectF(0, 0, viewWidth, viewHeight);
    var bufferRect = new RectF(0, 0, previewSize.Height, previewSize.Width);
    float centerX = viewRect.CenterX();
    float centerY = viewRect.CenterY();

    //Set the scale accordingly, to have the preview texture view fill the whole screen with cutting of the least amount of the preview as possible 
    //(but this way we keep the aspect ratio -> no preview distortion)
    bool isLandscape = ((int)SurfaceOrientation.Rotation90 == rotation || (int)SurfaceOrientation.Rotation270 == rotation);
    float scale;

    if (isLandscape)
    {
        scale = System.Math.Max(
            (float)viewWidth / previewSize.Height,
            (float)viewWidth / previewSize.Width);
    }
    else
    {
         scale = System.Math.Max(
            (float)viewHeight / previewSize.Height,
            (float)viewHeight / previewSize.Width);
    }


    if ((int)SurfaceOrientation.Rotation90 == rotation || (int)SurfaceOrientation.Rotation270 == rotation || (int)SurfaceOrientation.Rotation180 == rotation)
    {
        bufferRect.Offset((centerX - bufferRect.CenterX()), (centerY - bufferRect.CenterY()));
        matrix.SetRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.Fill);
        matrix.PostScale(scale, scale, centerX, centerY);

        //Small check if orientation is Reverse Portrait -> dont substract 2 from rotation, otherwise the preview is flipped by 180°
        if ((int)SurfaceOrientation.Rotation180 == rotation)
            matrix.PostRotate(90 * rotation, centerX, centerY);
        else
            matrix.PostRotate(90 * (rotation - 2), centerX, centerY);
    }
    TextureView.SetTransform(matrix);
}