Android相机预览拉伸

Question

我一直在努力在Android上制作我的自定义相机活动，但当旋转相机时，表面视图的纵横比会变得混乱。

在我的oncreate for the activity中，我设置了framelayout，它保存了显示相机参数的曲面视图。

//FrameLayout that will hold the camera preview
        FrameLayout previewHolder = (FrameLayout) findViewById(R.id.camerapreview);

        //Setting camera's preview size to the best preview size
        Size optimalSize = null;
        camera = getCameraInstance();
        double aspectRatio = 0;
        if(camera != null){
            //Setting the camera's aspect ratio
            Camera.Parameters parameters = camera.getParameters();
            List<Size> sizes = parameters.getSupportedPreviewSizes();
            optimalSize = CameraPreview.getOptimalPreviewSize(sizes, getResources().getDisplayMetrics().widthPixels, getResources().getDisplayMetrics().heightPixels);
            aspectRatio = (float)optimalSize.width/optimalSize.height;
        }

        if(optimalSize!= null){
            RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.MATCH_PARENT, (int)(getResources().getDisplayMetrics().widthPixels*aspectRatio));
            previewHolder.setLayoutParams(params);
            LayoutParams surfaceParams = new LayoutParams(LayoutParams.MATCH_PARENT, (int)(getResources().getDisplayMetrics().widthPixels*aspectRatio));
            cameraPreview.setLayoutParams(surfaceParams);

        }

        cameraPreview.setCamera(camera);

        //Adding the preview to the holder
        previewHolder.addView(cameraPreview);

然后，在曲面视图中，我设置要显示的相机参数

public void setCamera(Camera camera) {
        if (mCamera == camera) { return; }

        mCamera = camera;

        if (mCamera != null) {
            requestLayout();

            try {
                mCamera.setPreviewDisplay(mHolder);
            } catch (IOException e) {
                e.printStackTrace();
            }


            if(mCamera != null){
                //Setting the camera's aspect ratio
                Camera.Parameters parameters = mCamera.getParameters();
                List<Size> sizes = parameters.getSupportedPreviewSizes();
                Size optimalSize = getOptimalPreviewSize(sizes, getResources().getDisplayMetrics().widthPixels, getResources().getDisplayMetrics().heightPixels);

                parameters.setPreviewSize(optimalSize.width, optimalSize.height);
                mCamera.setParameters(parameters);
            }

            /*
              Important: Call startPreview() to start updating the preview surface. Preview must 
              be started before you can take a picture.
              */
            mCamera.startPreview();
        }

    }

您可以看到，当手机旋转时，乐高男会变得更高、更瘦：

如何确保相机视图的纵横比正确？

Answer 1

注：我的解决方案是HESAM解决方案的延续：https://stackoverflow.com/a/22758359/1718734

我的地址：Hesam说有些手机上可能会出现一些空白，如下所示：

Hesam提出了第二种解决方案，但这会挤压预览。在某些设备上，它会严重扭曲。

那么我们如何解决这个问题呢。这很简单。。。将纵横比相乘，直到填满屏幕。我注意到，Snapchat、WhatsApp等几种流行应用程序的工作方式都是一样的。

您所要做的就是将其添加到onInstrure方法中：

float camHeight = (int) (width * ratio);
    float newCamHeight;
    float newHeightRatio;

    if (camHeight < height) {
        newHeightRatio = (float) height / (float) mPreviewSize.height;
        newCamHeight = (newHeightRatio * camHeight);
        Log.e(TAG, camHeight + " " + height + " " + mPreviewSize.height + " " + newHeightRatio + " " + newCamHeight);
        setMeasuredDimension((int) (width * newHeightRatio), (int) newCamHeight);
        Log.e(TAG, mPreviewSize.width + " | " + mPreviewSize.height + " | ratio - " + ratio + " | H_ratio - " + newHeightRatio + " | A_width - " + (width * newHeightRatio) + " | A_height - " + newCamHeight);
    } else {
        newCamHeight = camHeight;
        setMeasuredDimension(width, (int) newCamHeight);
        Log.e(TAG, mPreviewSize.width + " | " + mPreviewSize.height + " | ratio - " + ratio + " | A_width - " + (width) + " | A_height - " + newCamHeight);
    }

这将计算屏幕高度，并获得屏幕高度与mPreviewSize高度的比率。然后将相机的宽度和高度乘以新的高度比，并相应地设置测量尺寸。

接下来你知道的是，你最终得到了这个： D

这也适用于前置摄像头。我相信这是最好的方法。现在，我的应用程序只剩下单击“捕获”保存预览本身但是，是的，就是这样。

Answer 2

F1Sher的解决方案很好，但有时不起作用。尤其是当你的surfaceView没有覆盖整个屏幕时。在这种情况下，需要重写onMeasure（）方法。我已将代码复制到这里供您参考。

因为我是根据宽度来测量surfaceView的，所以我在屏幕的末端有一点白色的间隙，我是通过设计来填充的。如果您保持高度并将其乘以比率来增加宽度，则可以解决此问题。然而，它会稍微挤压surfaceView。

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

    private static final String TAG = "CameraPreview";

    private Context mContext;
    private SurfaceHolder mHolder;
    private Camera mCamera;
    private List<Camera.Size> mSupportedPreviewSizes;
    private Camera.Size mPreviewSize;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mContext = context;
        mCamera = camera;

        // supported preview sizes
        mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
        for(Camera.Size str: mSupportedPreviewSizes)
                Log.e(TAG, str.width + "/" + str.height);

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // empty. surfaceChanged will take care of stuff
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // empty. Take care of releasing the Camera preview in your activity.
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        Log.e(TAG, "surfaceChanged => w=" + w + ", h=" + h);
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.
        if (mHolder.getSurface() == null){
            // preview surface does not exist
            return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
            // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or reformatting changes here
        // start preview with new settings
        try {
            Camera.Parameters parameters = mCamera.getParameters();
            parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
            mCamera.setParameters(parameters);
            mCamera.setDisplayOrientation(90);
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
        final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);

        if (mSupportedPreviewSizes != null) {
            mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
        }

        if (mPreviewSize!=null) {
            float ratio;
            if(mPreviewSize.height >= mPreviewSize.width)
                ratio = (float) mPreviewSize.height / (float) mPreviewSize.width;
            else
                ratio = (float) mPreviewSize.width / (float) mPreviewSize.height;

            // One of these methods should be used, second method squishes preview slightly
            setMeasuredDimension(width, (int) (width * ratio));
  //        setMeasuredDimension((int) (width * ratio), height);
        }
    }

    private Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {
        final double ASPECT_TOLERANCE = 0.1;
        double targetRatio = (double) h / w;

        if (sizes == null)
            return null;

        Camera.Size optimalSize = null;
        double minDiff = Double.MAX_VALUE;

        int targetHeight = h;

        for (Camera.Size size : sizes) {
            double ratio = (double) size.height / size.width;
            if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE)
                continue;

            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }

        if (optimalSize == null) {
            minDiff = Double.MAX_VALUE;
            for (Camera.Size size : sizes) {
                if (Math.abs(size.height - targetHeight) < minDiff) {
                    optimalSize = size;
                    minDiff = Math.abs(size.height - targetHeight);
                }
            }
        }

        return optimalSize;
    }
}

Answer 3

我在用这个方法-

private Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {
        final double ASPECT_TOLERANCE = 0.1;
        double targetRatio=(double)h / w;

        if (sizes == null) return null;

        Camera.Size optimalSize = null;
        double minDiff = Double.MAX_VALUE;

        int targetHeight = h;

        for (Camera.Size size : sizes) {
            double ratio = (double) size.width / size.height;
            if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }

        if (optimalSize == null) {
            minDiff = Double.MAX_VALUE;
            for (Camera.Size size : sizes) {
                if (Math.abs(size.height - targetHeight) < minDiff) {
                    optimalSize = size;
                    minDiff = Math.abs(size.height - targetHeight);
                }
            }
        }
        return optimalSize;
    }

正如您所看到的，您必须输入屏幕的宽度和高度。此方法将根据这些值计算屏幕比率，然后从支持的预览大小列表中选择最适合您的可用大小。在相机对象不为空的地方，使用

mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();

然后在onMeasure中，您可以获得如下最佳预览大小：

@Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
        final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
        setMeasuredDimension(width, height);

        if (mSupportedPreviewSizes != null) {
           mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
        }
    }

然后（在我的surfaceChanged方法中的代码中，就像我说的，我正在使用CameraActivity代码的API演示结构，您可以在Eclipse中生成它）：

Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
mCamera.setParameters(parameters);
mCamera.startPreview();

给你一个提示，因为我和你做了几乎相同的应用程序。相机活动的良好做法是隐藏StatusBar。Instagram等应用程序正在这样做。它会降低您的屏幕高度值并改变您的比率值。在某些设备上可能会出现奇怪的预览尺寸（您的SurfaceView会被削减一点）

为了回答您的问题，如何检查预览比率是否正确？然后获取在中设置的参数的高度和宽度：

mCamera.setParameters(parameters);

您的设置比率等于高度/宽度。如果您希望相机在屏幕上看起来不错，那么您设置给相机的参数的高度/宽度比率必须与屏幕的高度（减去状态栏）/宽度比率相同。