关于ios:iOS-拍照录频画质问题相关

后面写了拍照、扫码、录视频的性能，后面要求性能实现即可，前面发现画质不够

可能起因剖析：

1.AVCaptureSession设置输入格局会影响画质清晰度

2.拍照中并未做聚焦/曝光解决, 或 聚焦/曝光设置参数导致含糊

解决

针对起因1，列举如下sessionPreset对应的像素(height *width):

AVCaptureSessionPresetHigh                  1920*1080AVCaptureSessionPresetMedium                480*360AVCaptureSessionPresetLow                   192*144AVCaptureSessionPresetPhoto                 4032*3024AVCaptureSessionPreset352x288               352*288AVCaptureSessionPreset640x480               640*480AVCaptureSessionPreset1280x720              1280*720AVCaptureSessionPreset1920x1080             1920*1080AVCaptureSessionPreset3840x2160             3840*2160AVCaptureSessionPresetiFrame960x540         960*540AVCaptureSessionPresetiFrame1280x720        1280*720AVCaptureSessionPresetInputPriority         1920*1080

按需来设置该参数

针对起因2，聚焦/曝光设置:

/* 必须先设置聚焦地位，再设定聚焦形式 */CGRect rectLayer = self.preView.frame;CGPoint ccenter = CGPointMake((rectLayer.origin.x + rectLayer.size.width) / 2, (rectLayer.origin.y + rectLayer.size.height) / 2);CGPoint cpoint = [self.preView captureDevicePointForPoint:ccenter];AVCaptureDevice *devices= [self.dInput device];[self.session beginConfiguration];[devices lockForConfiguration:nil];// 设置聚焦点的地位if ([devices isFocusPointOfInterestSupported]) {    [devices setFocusPointOfInterest:cpoint];}// 设置聚焦模式if ([devices isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus]) {    [devices setFocusMode:AVCaptureFocusModeContinuousAutoFocus];}// 设置曝光点的地位if ([devices isExposurePointOfInterestSupported]) {    [devices setExposurePointOfInterest:cpoint];}// 设置曝光模式if ([devices isExposureModeSupported:AVCaptureExposureModeContinuousAutoExposure]) {    [devices setExposureMode:AVCaptureExposureModeContinuousAutoExposure];}[device unlockForConfiguration];[self.session commitConfiguration];

其中聚焦模式 跟曝光模式的设置很有意思：

typedef NS_ENUM(NSInteger, AVCaptureFocusMode) {    // 将焦点锁定在镜头的以后地位    AVCaptureFocusModeLocked              = 0,    // 设施应主动对焦一次，而后将对焦模式更改为AVCaptureFocusModeLocked    AVCaptureFocusModeAutoFocus           = 1,    // 设施应在须要时主动对焦    AVCaptureFocusModeContinuousAutoFocus = 2,}typedef NS_ENUM(NSInteger, AVCaptureExposureMode) {    // 将曝光锁定在其以后值    AVCaptureExposureModeLocked                            = 0,    // 主动调整一次曝光，而后将曝光模式更改为AVCaptureExposureModeLocked    AVCaptureExposureModeAutoExpose                        = 1,    // 在须要时主动调整曝光    AVCaptureExposureModeContinuousAutoExposure            = 2,    // 仅依据用户提供的ISO，DurationDuration值来调整曝光    AVCaptureExposureModeCustom API_AVAILABLE(macos(10.15), ios(8.0)) = 3,}

当我设置聚焦模式 = AVCaptureFocusModeAutoFocus，曝光模式 = AVCaptureExposureModeAutoExpose，会有聚焦的过程，但跟零碎拍照有差距。

调试下参数别离为ContinuousAuto模式后，画质清晰度跟零碎拍照差不多了。