使用AVFoundation自定义相机如何调整相机焦距

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1、如何使用AVFoundation框架自定义相机请先参照iOS项目实战之自定义相机

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：

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/// 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。

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

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/// 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

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//
//? 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 SAAVFoundation

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