Camera 开发实战(一)——预览尺寸的选取与旋转角度的设定

private final SizeMap mPreviewSizes = new SizeMap();

// 变量所有的预览尺寸, 按照比例分类
for (Camera.Size size : mCameraParams.getSupportedPreviewSizes()) {
    mPreviewSizes.add(new Size(size.width, size.height));
}

class SizeMap {

    private final ArrayMap<AspectRatio, SortedSet<Size>> mRatios = new ArrayMap<>();

    /**
     * Add a new {@link Size} to this collection.
     *
     * @param size The size to add.
     * @return {@code true} if it is added, {@code false} if it already exists and is not added.
     */
    public boolean add(Size size) {
        for (AspectRatio ratio : mRatios.keySet()) {
            if (ratio.matches(size)) {
                final SortedSet<Size> sizes = mRatios.get(ratio);
                if (sizes.contains(size)) {
                    return false;
                } else {
                    sizes.add(size);
                    return true;
                }
            }
        }
        // None of the existing ratio matches the provided size; add a new key
        SortedSet<Size> sizes = new TreeSet<>();
        sizes.add(size);
        mRatios.put(AspectRatio.of(size.getWidth(), size.getHeight()), sizes);
        return true;
    }

}

// 1. 获取用户期望的比例的集合
SortedSet<Size> previewSizes = mPreviewSizes.sizes(aspectRatio);
if (previewSizes == null) {
    // 1.1 用户期望的比例不存在, 选取获取默认比例
    previewSizes = mPreviewSizes.sizes(chooseDefaultAspectRatio());
}
// 2. 选择最合适的预览帧尺寸
final Size previewSize = chooseOptimalPreviewSize(previewSizes);
// 参数注入
mCameraParams.setPreviewSize(previewSize.getWidth(), previewSize.getHeight());

private AspectRatio chooseDefaultAspectRatio() {
    AspectRatio result = null;
    for (AspectRatio ratio : mPreviewSizes.ratios()) {
        result = ratio;
        if (AspectRatio.DEFAULT.equals(ratio)) {
            break;
        }
    }
    return result;
}

 E/TAG: desire aspect is 1:1, closely is 11:9
 E/TAG: desired size is: [1080, 1080]; choose preview size is: [352x288]

private Size chooseOptimalPreviewSize(SortedSet<Size> sizes) {
    // 1. 确定期望的宽高
    int desiredWidth;
    int desiredHeight;
    // 横屏状态, 直接使用 view 的宽高
    if (isLandscape(screenOrientationDegrees)) {
        desiredWidth = viewWidth;
        desiredHeight = viewHeight;
    }
    // 竖屏状态, 反转宽高
    else {
        desiredWidth = viewHeight;
        desiredHeight = viewWidth;
    }
    // 2. 查找最合适的预览尺寸
    Size result = null;
    for (Size size : sizes) {// sizes 已按照从小到大排序
        result = size;
        // 选取宽高都比期望稍大的
        if (desiredWidth <= size.getWidth() && desiredHeight <= size.getHeight()) {
            return size;
        }
    }
    return result;
}

// 期望比例 4:3
E/TAG: desired size is: [1440, 1080]; choose preview size is: [1600x1200]
 
// 期望比例 16:19
E/TAG: desired size is: [1920, 1080]; choose preview size is: [1920x1080]

// 期望比例 1:1
E/TAG: desired size is: [1440, 1080]; choose preview size is: [1600x1200]

public class Camera {
    
    /**
     * ......
     * <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>
     * ......
     */
    public native final void setDisplayOrientation(int degrees);
    
}

public class Camera {
    
     public static class CameraInfo {
        /**
         * <p>The orientation of the camera image. The value is the angle that the
         * camera image needs to be rotated clockwise so it shows correctly on
         * the display in its natural orientation. It should be 0, 90, 180, or 270.</p>
         *
         * <p>For example, suppose a device has a naturally tall screen. The
         * back-facing camera sensor is mounted in landscape. You are looking at
         * the screen. If the top side of the camera sensor is aligned with the
         * right edge of the screen in natural orientation, the value should be
         * 90. If the top side of a front-facing camera sensor is aligned with
         * the right of the screen, the value should be 270.</p>
         *
         * .......
         */
        public int orientation;
    }
}

public static void setCameraDisplayOrientation(Activity activity,
        int cameraId, android.hardware.Camera camera) {
    ......
    int degrees = 0;
    ......
    int result;
    if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
        ......
    } 
    // back-facing
    else {
        result = (info.orientation - degrees + 360) % 360;
    }
    camera.setDisplayOrientation(result);
}

public static void setCameraDisplayOrientation(Activity activity,
        int cameraId, android.hardware.Camera camera) {
    ......
    int degrees = 0;
    ......
    int result;
    if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
        result = (info.orientation + degrees) % 360;
        result = (360 - result) % 360;  // 抵消镜像
    } 
    // back-facing
    else {
        ......
    }
    camera.setDisplayOrientation(result);
}

PreviewConfig config = new PreviewConfig.Builder()
         // CameraX 的宽高比和 Camera1 相反, 为 3:4 9:16......
         .setTargetAspectRatio(new Rational(aspectRatio.getY(), aspectRatio.getX()))
         // 分辨率
         .setTargetResolution(new android.util.Size(previewWidth, previewHeight))
         // 前置与否
         .setLensFacing(facing == Constants.FACING_FRONT ? CameraX.LensFacing.FRONT
                 : CameraX.LensFacing.BACK)
         .build();
Preview preview = new Preview(config);
CameraX.bindToLifecycle(mLifecycleOwner, preview);