制作视频填充屏幕并保持宽高比答案

【问题标题】：Make video fill screen and keep aspect ratio制作视频填充屏幕并保持宽高比
【发布时间】：2018-03-08 11:04:58
【问题描述】：

接受 Java 和 C# (Xamarin.Android)

我有一个 MediaRecorder，可以将相机帧流式传输到 TextureView（基本的 camera2 方法）
TextureView 填满了我的屏幕。

我希望视频填满屏幕但保持宽高比。

我知道我最终必须剪切视频的左/右或上/下部分，以保持纵横比。

如何使视频适合 TextureView 并“放大”直到填满整个屏幕？我不希望为了保持比率而妥协的“黑条”。

我想这必须通过覆盖 TextureView 的 OnMeasure 来完成

C# 扩展 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);
                }
            }
        }

【问题讨论】：

如果你能提供一个minimal reproducible example 你迄今为止的工作，那就太棒了。
我添加了相应地缩放纹理视图的代码。我实际上说我的纹理视图填满了屏幕，事实并非如此。
我认为这篇文章为我的答案提供了一个解决方案，但它是一个更大的帖子，现在必须通过它。 stackoverflow.com/questions/17019588/…

标签： java c# fill aspect-ratio textureview

【解决方案1】：

感谢this post的this comment，我找到了答案。

C# Xamarin.Android：

当我的表面纹理大小发生变化时，我调用以下方法（SurfaceTextureListener 中的OnSurfaceSizeTextureChanged 回调）

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);
}

【讨论】：