java source code of CameraConfigurationManager

/*
 * Copyright (C) 2008 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package zxing.camera;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Point;
import android.hardware.Camera;
import android.util.Log;
import android.view.Display;
import android.view.WindowManager;

public final class CameraConfigurationManager {

	private static final String TAG = "CameraConfiguration";

	private static final int MIN_PREVIEW_PIXELS = 480 * 320;
	private static final double MAX_ASPECT_DISTORTION = 0.15;

	private final Context context;

	// 屏幕分辨率
	private Point screenResolution;
	// 相机分辨率
	private Point cameraResolution;

	public CameraConfigurationManager(Context context) {
		this.context = context;
	}

	public void initFromCameraParameters(Camera camera) {
		Camera.Parameters parameters = camera.getParameters();
		WindowManager manager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
		Display display = manager.getDefaultDisplay();
		Point theScreenResolution = new Point();
		theScreenResolution = getDisplaySize(display);

		screenResolution = theScreenResolution;
		Log.i(TAG, "Screen resolution: " + screenResolution);

		/** 因为换成了竖屏显示，所以不替换屏幕宽高得出的预览图是变形的 */
		Point screenResolutionForCamera = new Point();
		screenResolutionForCamera.x = screenResolution.x;
		screenResolutionForCamera.y = screenResolution.y;

		if (screenResolution.x < screenResolution.y) {
			screenResolutionForCamera.x = screenResolution.y;
			screenResolutionForCamera.y = screenResolution.x;
		}

		cameraResolution = findBestPreviewSizeValue(parameters, screenResolutionForCamera);
		Log.i(TAG, "Camera resolution x: " + cameraResolution.x);
		Log.i(TAG, "Camera resolution y: " + cameraResolution.y);
	}

	@SuppressLint("NewApi")
	private Point getDisplaySize(final Display display) {
		final Point point = new Point();
		try {
			display.getSize(point);
		} catch (java.lang.NoSuchMethodError ignore) {
			point.x = display.getWidth();
			point.y = display.getHeight();
		}
		return point;
	}

	public void setDesiredCameraParameters(Camera camera, boolean safeMode) {
		Camera.Parameters parameters = camera.getParameters();

		if (parameters == null) {
			Log.w(TAG, "Device error: no camera parameters are available. Proceeding without configuration.");
			return;
		}

		Log.i(TAG, "Initial camera parameters: " + parameters.flatten());

		if (safeMode) {
			Log.w(TAG, "In camera config safe mode -- most settings will not be honored");
		}

		parameters.setPreviewSize(cameraResolution.x, cameraResolution.y);
		camera.setParameters(parameters);

		Camera.Parameters afterParameters = camera.getParameters();
		Camera.Size afterSize = afterParameters.getPreviewSize();
		if (afterSize != null && (cameraResolution.x != afterSize.width || cameraResolution.y != afterSize.height)) {
			Log.w(TAG, "Camera said it supported preview size " + cameraResolution.x + 'x' + cameraResolution.y + ", but after setting it, preview size is " + afterSize.width + 'x' + afterSize.height);
			cameraResolution.x = afterSize.width;
			cameraResolution.y = afterSize.height;
		}

		/** 设置相机预览为竖屏 */
		String model=android.os.Build.MODEL;
		if("Nexus 5X".equals(model)){
			camera.setDisplayOrientation(270);
		}else{
			camera.setDisplayOrientation(90);
		}
	
	}

	public Point getCameraResolution() {
		return cameraResolution;
	}

	public Point getScreenResolution() {
		return screenResolution;
	}

	/**
	 * 从相机支持的分辨率中计算出最适合的预览界面尺寸
	 * 
	 * @param parameters
	 * @param screenResolution
	 * @return
	 */
	private Point findBestPreviewSizeValue(Camera.Parameters parameters, Point screenResolution) {
		List<Camera.Size> rawSupportedSizes = parameters.getSupportedPreviewSizes();
		if (rawSupportedSizes == null) {
			Log.w(TAG, "Device returned no supported preview sizes; using default");
			Camera.Size defaultSize = parameters.getPreviewSize();
			return new Point(defaultSize.width, defaultSize.height);
		}

		// Sort by size, descending
		List<Camera.Size> supportedPreviewSizes = new ArrayList<Camera.Size>(rawSupportedSizes);
		Collections.sort(supportedPreviewSizes, new Comparator<Camera.Size>() {
			@Override
			public int compare(Camera.Size a, Camera.Size b) {
				int aPixels = a.height * a.width;
				int bPixels = b.height * b.width;
				if (bPixels < aPixels) {
					return -1;
				}
				if (bPixels > aPixels) {
					return 1;
				}
				return 0;
			}
		});

		if (Log.isLoggable(TAG, Log.INFO)) {
			StringBuilder previewSizesString = new StringBuilder();
			for (Camera.Size supportedPreviewSize : supportedPreviewSizes) {
				previewSizesString.append(supportedPreviewSize.width).append('x').append(supportedPreviewSize.height).append(' ');
			}
			Log.i(TAG, "Supported preview sizes: " + previewSizesString);
		}

		double screenAspectRatio = (double) screenResolution.x / (double) screenResolution.y;

		// Remove sizes that are unsuitable
		Iterator<Camera.Size> it = supportedPreviewSizes.iterator();
		while (it.hasNext()) {
			Camera.Size supportedPreviewSize = it.next();
			int realWidth = supportedPreviewSize.width;
			int realHeight = supportedPreviewSize.height;
			if (realWidth * realHeight < MIN_PREVIEW_PIXELS) {
				it.remove();
				continue;
			}

			boolean isCandidatePortrait = realWidth < realHeight;
			int maybeFlippedWidth = isCandidatePortrait ? realHeight : realWidth;
			int maybeFlippedHeight = isCandidatePortrait ? realWidth : realHeight;

			double aspectRatio = (double) maybeFlippedWidth / (double) maybeFlippedHeight;
			double distortion = Math.abs(aspectRatio - screenAspectRatio);
			if (distortion > MAX_ASPECT_DISTORTION) {
				it.remove();
				continue;
			}

			if (maybeFlippedWidth == screenResolution.x && maybeFlippedHeight == screenResolution.y) {
				Point exactPoint = new Point(realWidth, realHeight);
				Log.i(TAG, "Found preview size exactly matching screen size: " + exactPoint);
				return exactPoint;
			}
		}

		// If no exact match, use largest preview size. This was not a great
		// idea on older devices because
		// of the additional computation needed. We're likely to get here on
		// newer Android 4+ devices, where
		// the CPU is much more powerful.
		if (!supportedPreviewSizes.isEmpty()) {
			Camera.Size largestPreview = supportedPreviewSizes.get(0);
			Point largestSize = new Point(largestPreview.width, largestPreview.height);
			Log.i(TAG, "Using largest suitable preview size: " + largestSize);
			return largestSize;
		}

		// If there is nothing at all suitable, return current preview size
		Camera.Size defaultPreview = parameters.getPreviewSize();
		Point defaultSize = new Point(defaultPreview.width, defaultPreview.height);
		Log.i(TAG, "No suitable preview sizes, using default: " + defaultSize);

		return defaultSize;
	}
}