使用AVFoundation自定义相机如何调整相机焦距

Sian

1、如何使用AVFoundation框架自定义相机请先参照 http://www.yusian.com/bbs/thread-10503-1-1.html

2.1、上述帖子中有讲到，如果需要对焦，可以通过AVCaptureDevice的setFocusPointOfInterest:方法来实现，传入一个CGPoint值，但这里的CGPoint不是View上面的点，而是范围的0~1的相对百分点；

2.2、这个CGPoint如何得来呢，我们在点击屏幕时可以监听相关View的点击事件，添加一个UITapGestureRecognizer手势，在点时后，可以通过UITapGestureRecognizer的locationInView:方法得到CGPoint，这是一个绝对值，即点击了相关View上的某个点，有了这个点，再通过AVCaptureVideoPreviewLayer的一个转换方法：captureDevicePointOfInterestForPoint:可以将绝对点转换成相对点。

2.3、得到CGPoint后，就可以调用AVCaptureDevice（即摄像头）的setFocusPointOfInterest:方法来实现了，但需要注意的是，这个方法不能直接调用，要分三步曲来完成：锁定AVCaptureDevice，修改参数值，解锁AVCaptureDevice。一般形式如：

[Objective-C] 纯文本查看 复制代码

/// 对焦事件
- (void)focusAtPoint:(CGPoint)point
{
    AVCaptureDevice *device = self.deviceInput.device;
    NSError *error;
    if ([device isFocusModeSupported:AVCaptureFocusModeAutoFocus] && [device isFocusPointOfInterestSupported])
    {
        if ([device lockForConfiguration:&error]) {
            [device setFocusPointOfInterest:point];     // 对焦点
            [device setExposurePointOfInterest:point];  // 曝光点
            [device setFocusMode:AVCaptureFocusModeAutoFocus];  // 自动对焦模式
            [device unlockForConfiguration];
        } else {
            NSLog(@"Error: %@", error);
        }
    }
}

3、自动对焦实现了，如何调节焦距呢？

3.1、这里所谓的调节焦距不是对焦的意思，而是在拍摄远景时所需要的放大（拉近）影像

3.2、有两种方式来实现，第一种方式，通过放大AVCaptureVideoPreviewLayer及AVCaptureStillImageOutput的videoScaleAndCropFactor属性来实现，简单一点讲就是把预览图层放大，这样在屏幕上就只能看到一部分影像了，然后在捕捉生成图片时做相同倍数的放大，裁剪超出部分的像素实现，这种方式好比原本拍摄的照片是4000*3000的分辨率，现在通过放大只取中间2000*1500的部分输出同样大小的照片，最终的效果就是放大了图像。（如果这部分看不懂，说明没有理解AVFoundation的工作原理，参照：http://www.yusian.com/bbs/thread-10580-1-1.html）

3.3、另一种方式，通过调节AVCaptureDevice的videoZoomFactor属性来实现焦距的调整，这种方式事实上是在图像取景的时候就进行了相关调整，取摄像头的部分影像进入sesstion，这样更合理，并且前面那种方式有个问题：因为是通过放大图层来模拟拉近焦距，所以实际上图层是不清晰的，对焦也没什么效果。然而第二种方式中videoZoomFactor属性需要iOS7以上才支持。

3.4、设置videoZoomFactor属性与对焦一样同样需要三部曲来实现，锁定Device、设置属性、解锁Device

[Objective-C] 纯文本查看 复制代码

/// 调整摄像头焦距
- (void)setDevice:(AVCaptureDevice *)device videoZoomFactor:(CGFloat)scale
{
    [device lockForConfiguration:nil];
    device.videoZoomFactor = scale;
    [device unlockForConfiguration];
}

4、关键代码示例：

[Objective-C] 纯文本查看 复制代码

//
//  SACameraCtrl.m
//  Test
//
//  Created by 余西安 on 15/4/13.
//  Copyright (c) 2015年 Sian. All rights reserved.
//

#import "SACameraCtrl.h"
#import "SAPreview.h"
#import "SAPhotoViewCtrl.h"
#import <AVFoundation/AVFoundation.h>
#import <CoreMotion/CoreMotion.h>
#define SourcePath [[NSBundle mainBundle] pathForResource:@"SAImagePickerController.bundle" ofType:nil]

@interface SACameraCtrl () <UIAccelerometerDelegate>
{
    CGFloat _deviceScale;
}
// 输入流预览图层
@property (nonatomic, strong)   AVCaptureVideoPreviewLayer  *previewLayer;

@property (weak, nonatomic) IBOutlet SAPreview *preview;

// AVCaptureSession对象来执行输入设备和输出设备之间的数据传递
@property (nonatomic, strong)   AVCaptureSession            *session;

// 设备输入流
@property (nonatomic, strong)   AVCaptureDeviceInput        *deviceInput;

// 照片输出流
@property (nonatomic, strong)   AVCaptureStillImageOutput   *imageOutput;

// 摄像头焦倍
@property (nonatomic, assign)   CGFloat         deviceScale;

// 图片输出视图
@property (nonatomic, strong)   UIImageView     *cameraShowView;

// 摄像头数组
@property (nonatomic, strong, readonly) NSArray     *devices;       // AVCaptureDevices

// 闪光灯切换按钮
@property (weak, nonatomic) IBOutlet    UIButton    *flashButton;

@end

@implementation SACameraCtrl

- (void)viewDidLoad
{
    [super viewDidLoad];
    // 创建交互流
    self.session = [[AVCaptureSession alloc] init];
    self.session.sessionPreset = AVCaptureSessionPresetPhoto;
    
    // 媒体输入
    AVCaptureDevice *device = [self.devices firstObject];
    [self setDevice:device FlashMode:AVCaptureFlashModeAuto];
    self.deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:NULL];
    if([self.session canAddInput:self.deviceInput])[self.session addInput:self.deviceInput];

    // 媒体输出
    self.imageOutput = [[AVCaptureStillImageOutput alloc] init];
    self.imageOutput.outputSettings = @{AVVideoCodecKey : AVVideoCodecJPEG};
    AVCaptureConnection * connection = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
    connection.videoOrientation = AVCaptureVideoOrientationLandscapeRight;
    if([self.session canAddOutput:self.imageOutput])[self.session addOutput:self.imageOutput];
    
    // 媒体预览
    self.previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.session];
    self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspect;
    [self.preview.layer addSublayer:self.previewLayer];
    [self setPreviewGesture];
}


#pragma mark - 前后摄像头
- (NSArray *)devices
{
    return [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    self.deviceScale = 1.0;
    self.previewLayer.frame = self.preview.layer.bounds;
    self.navigationController.navigationBar.hidden = YES;
    [self setDevice:self.deviceInput.device videoZoomFactor:self.deviceScale];
    [self.session startRunning];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    [[UIApplication sharedApplication] setStatusBarHidden:YES];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [[UIApplication sharedApplication] setStatusBarHidden:NO];
}

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
    [self.session stopRunning];
}

/// 媒体预览图层手势事件
- (void)setPreviewGesture
{
    // 注册一个手势事件来实现对焦功能
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapPreview:)];
    UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchPreview:)];
    [self.preview addGestureRecognizer:tap];
    if ([UIDevice currentDevice].systemVersion.floatValue >= 7.0) [self.preview addGestureRecognizer:pinch];
}

/// 预览图层点击事件
- (void)tapPreview:(UITapGestureRecognizer *)gesture
{
    CGPoint point = [gesture locationInView:gesture.view];
    CGPoint p = [self.previewLayer captureDevicePointOfInterestForPoint:point];
    [self focusAtPoint:p];
    // 对焦动画
    self.preview.aperture.center = point;
    [self.preview showAperture];
}

/// 焦距调整事件
- (void)pinchPreview:(UIPinchGestureRecognizer *)gesture
{
    CGFloat scale = self.deviceScale + (gesture.scale - 1);
    if (scale > 5) scale = 5;   // 最大5倍焦距
    if (scale < 1) scale = 1;   // 最小1倍焦距
    [self setDevice:self.deviceInput.device videoZoomFactor:scale];
    // 缩放结束时记录当前倍焦
    if (gesture.state == UIGestureRecognizerStateEnded) self.deviceScale = scale;
}

/// 对焦事件
- (void)focusAtPoint:(CGPoint)point
{
    AVCaptureDevice *device = self.deviceInput.device;
    NSError *error;
    if ([device isFocusModeSupported:AVCaptureFocusModeAutoFocus] && [device isFocusPointOfInterestSupported])
    {
        if ([device lockForConfiguration:&error]) {
            [device setFocusPointOfInterest:point];     // 对焦点
            [device setExposurePointOfInterest:point];  // 曝光点
            [device setFocusMode:AVCaptureFocusModeAutoFocus];  // 自动对焦模式
            [device unlockForConfiguration];
        } else {
            NSLog(@"Error: %@", error);
        }
    }
}

/// 摄像头切换事件
- (IBAction)switchCamera:(UIButton *)sender
{
    if (self.devices.count < 2) return;
    
    NSInteger oldIndex = [self.devices indexOfObject:self.deviceInput.device];
    NSInteger newIndex = (oldIndex + 1) % self.devices.count;
    AVCaptureDevice *newDevice = [self.devices objectAtIndex:newIndex];
    AVCaptureDeviceInput *newInput = [AVCaptureDeviceInput deviceInputWithDevice:newDevice error:NULL];
    if (newInput) {
        [self.session beginConfiguration];
        [self.session removeInput:self.deviceInput];
        [self.session addInput:newInput];
        [self.session commitConfiguration];
        self.deviceInput = newInput;
        self.flashButton.hidden = !newDevice.isFlashAvailable;
    }
}

/// 取消事件
- (IBAction)cancel:(UIButton *)sender
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

/// 拍照事件
- (IBAction)shutter:(UIButton *)sender
{
    sender.userInteractionEnabled = NO;
    AVCaptureConnection * connection = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
    connection.videoOrientation = AVCaptureVideoOrientationPortrait;
    connection.videoScaleAndCropFactor = 1.0;   // 获取流比例
    if (!connection) {
        NSLog(@"take photo failed!");
        return;
    }
    
    [self.imageOutput captureStillImageAsynchronouslyFromConnection:connection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
        if (imageDataSampleBuffer == NULL) {
            return;
        }
        NSData * imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
        UIImage * image = [UIImage imageWithData:imageData];
        SAPhotoViewCtrl *photoView = [[SAPhotoViewCtrl alloc] initWithImage:image];
        [self.navigationController pushViewController:photoView animated:NO];
        sender.userInteractionEnabled = YES;
    }];
}

/// 调整摄像头焦距
- (void)setDevice:(AVCaptureDevice *)device videoZoomFactor:(CGFloat)scale
{
    [device lockForConfiguration:nil];
    device.videoZoomFactor = scale;
    [device unlockForConfiguration];
}

/// 闪光灯开关按钮
- (IBAction)overTurn:(UIButton *)sender
{
    sender.tag = (sender.tag + 1) % 3;
    NSString *imageName = [NSString stringWithFormat:@"camera_flashlight_%d.png", (int)sender.tag];
    [sender setBackgroundImage:[UIImage imageNamed:imageName] forState:UIControlStateNormal];
    [self setDevice:self.deviceInput.device FlashMode:(2 - sender.tag)];
}

/// 切换闪光灯模式
- (void)setDevice:(AVCaptureDevice *)device FlashMode:(AVCaptureFlashMode)flashModel
{
    if (device.isFlashAvailable == NO) return;
    if ([device lockForConfiguration:nil]) {
        device.flashMode = flashModel;
    }
    [device unlockForConfiguration];
}

@end

5、Demo下载

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