Android Camera开发系列：调整Camera预览方向
<p>有时候我们想根据自己的需要调整下Camera的预览方向，那么是调用哪个API可以达到我们的目的呢？</p><p>我们看下下图拍的几张小可爱的照片，分别是正常方向、旋转180度、90度拍的照片。<br>
<img src="https://upload-images.jianshu.io/upload_images/16344730-e128564ad393c519?imageMogr2/auto-orient/strip%7CimageView2/2/w/200"></p>
<p><img src="https://upload-images.jianshu.io/upload_images/16344730-a4cabb6fb3a4dbd4?imageMogr2/auto-orient/strip%7CimageView2/2/w/200"></p>
<p><img src="https://upload-images.jianshu.io/upload_images/16344730-6e67716d589d9fd7?imageMogr2/auto-orient/strip%7CimageView2/2/w/200"></p>
<h3 id="一camera-api">一、Camera API</h3>
<p>Camera1上，我们可以通过<strong>setDisplayOrientation（int degress）；</strong>来设置camera预览的方向。</p>
<pre><code>mCamera.setDisplayOrientation(Surface.ROTATION_180);
</code></pre>
<p>这里也贴下源码里面关于setDisplayOrientaion接口的详细说明。</p>
<pre><code> /**
* Set the clockwise rotation of preview display in degrees. This affects
* the preview frames and the picture displayed after snapshot. This method
* is useful for portrait mode applications. Note that preview display of
* front-facing cameras is flipped horizontally before the rotation, that
* is, the image is reflected along the central vertical axis of the camera
* sensor. So the users can see themselves as looking into a mirror.
*
* <p>This does not affect the order of byte array passed in {@link
* PreviewCallback#onPreviewFrame}, JPEG pictures, or recorded videos. This
* method is not allowed to be called during preview.
*
* <p>If you want to make the camera image show in the same orientation as
* the display, you can use the following code.
* <pre>
* public static void setCameraDisplayOrientation(Activity activity,
* int cameraId, android.hardware.Camera camera) {
* android.hardware.Camera.CameraInfo info =
* new android.hardware.Camera.CameraInfo();
* android.hardware.Camera.getCameraInfo(cameraId, info);
* int rotation = activity.getWindowManager().getDefaultDisplay()
* .getRotation();
* int degrees = 0;
* switch (rotation) {
* case Surface.ROTATION_0: degrees = 0; break;
* case Surface.ROTATION_90: degrees = 90; break;
* case Surface.ROTATION_180: degrees = 180; break;
* case Surface.ROTATION_270: degrees = 270; break;
* }
*
* int result;
* if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
* result = (info.orientation + degrees) % 360;
* result = (360 - result) % 360;// compensate the mirror
* } else {// back-facing
* result = (info.orientation - degrees + 360) % 360;
* }
* camera.setDisplayOrientation(result);
* }
* </pre>
*
* <p>Starting from API level 14, this method can be called when preview is
* active.
*
* <p><b>Note: </b>Before API level 24, the default value for orientation is 0\. Starting in
* API level 24, the default orientation will be such that applications in forced-landscape mode
* will have correct preview orientation, which may be either a default of 0 or
* 180\. Applications that operate in portrait mode or allow for changing orientation must still
* call this method after each orientation change to ensure correct preview display in all
* cases.</p>
*
* @param degrees the angle that the picture will be rotated clockwise.
* Valid values are 0, 90, 180, and 270.
* @throws RuntimeException if setting orientation fails; usually this would
* be because of a hardware or other low-level error, or because
* release() has been called on this Camera instance.
* @see #setPreviewDisplay(SurfaceHolder)
*/
public native final void setDisplayOrientation(int degrees);
</code></pre>
<h3 id="二camera2-api"><strong>二、Camera2 API</strong></h3>
<p>Camera2的API上，找了一通，发现并没有像Camera1上，可以通过类似的接口来设置预览方向，不过可以通过TextureView.setTransform(matrix);来通过调整textureView的显示来达到目的。</p>
<pre><code>public void openCamera(){
CameraManager manager = (CameraManager) mContext.getSystemService(Context.CAMERA_SERVICE);
try {
......
//调整预览画面显示方向
configureTextureViewTransform(mTextureView.getWidth(),mTextureView.getHeight());
manager.openCamera(cameraId, mStateCallback, null);
......
}
}
private void configureTextureViewTransform(int viewWidth, int viewHeight) {
if (null == mTextureView) {
return;
}
int rotation = 0 ;/*activity.getWindowManager().getDefaultDisplay().getRotation();*/
Matrix matrix = new Matrix();
RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);
RectF bufferRect = new RectF(0, 0, mPreviewSize.getHeight(), mPreviewSize.getWidth());
float centerX = viewRect.centerX();
float centerY = viewRect.centerY();
if (Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation) {
bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());
matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);
float scale = Math.max(
(float) viewHeight / mPreviewSize.getHeight(),
(float) viewWidth / mPreviewSize.getWidth());
matrix.postScale(scale, scale, centerX, centerY);
matrix.postRotate(90 * (rotation - 2), centerX, centerY);
}else if (Surface.ROTATION_180 == rotation) {
matrix.postRotate(180, centerX, centerY);
}
mTextureView.setTransform(matrix);
}
</code></pre>
<p>=======================================================================</p>
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<p><img src="https://img2020.cnblogs.com/blog/2279751/202101/2279751-20210113164428529-1663209907.png"></p><br><br>
来源：https://www.cnblogs.com/york-zhou/p/14273314.html
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