96 lines
3.3 KiB
Objective-C
96 lines
3.3 KiB
Objective-C
//
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// SCManagedCaptureDeviceSavitzkyGolayZoomHandler.m
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// Snapchat
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//
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// Created by Yu-Kuan Lai on 4/12/17.
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// Copyright © 2017 Snapchat, Inc. All rights reserved.
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// https://en.wikipedia.org/wiki/Savitzky%E2%80%93Golay_filter
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//
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#import "SCManagedCaptureDeviceSavitzkyGolayZoomHandler.h"
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#import "SCManagedCaptureDevice.h"
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#import "SCManagedCaptureDeviceDefaultZoomHandler_Private.h"
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#import <SCFoundation/SCQueuePerformer.h>
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#import <SCFoundation/SCTraceODPCompatible.h>
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static NSUInteger const kSCSavitzkyGolayWindowSize = 9;
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static CGFloat const kSCUpperSharpZoomThreshold = 1.15;
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@interface SCManagedCaptureDeviceSavitzkyGolayZoomHandler ()
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@property (nonatomic, strong) NSMutableArray *zoomFactorHistoryArray;
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@end
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@implementation SCManagedCaptureDeviceSavitzkyGolayZoomHandler
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- (instancetype)initWithCaptureResource:(SCCaptureResource *)captureResource
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{
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self = [super initWithCaptureResource:captureResource];
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if (self) {
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_zoomFactorHistoryArray = [[NSMutableArray alloc] init];
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}
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return self;
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}
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- (void)setZoomFactor:(CGFloat)zoomFactor forDevice:(SCManagedCaptureDevice *)device immediately:(BOOL)immediately
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{
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if (self.currentDevice != device) {
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// reset if device changed
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self.currentDevice = device;
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[self _resetZoomFactor:zoomFactor forDevice:self.currentDevice];
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return;
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}
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if (immediately || zoomFactor == 1 || _zoomFactorHistoryArray.count == 0) {
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// reset if zoomFactor is 1 or this is the first data point
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[self _resetZoomFactor:zoomFactor forDevice:device];
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return;
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}
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CGFloat lastVal = [[_zoomFactorHistoryArray lastObject] floatValue];
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CGFloat upperThreshold = lastVal * kSCUpperSharpZoomThreshold;
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if (zoomFactor > upperThreshold) {
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// sharp change in zoomFactor, reset
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[self _resetZoomFactor:zoomFactor forDevice:device];
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return;
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}
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[_zoomFactorHistoryArray addObject:@(zoomFactor)];
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if ([_zoomFactorHistoryArray count] > kSCSavitzkyGolayWindowSize) {
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[_zoomFactorHistoryArray removeObjectAtIndex:0];
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}
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float filteredZoomFactor =
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SC_CLAMP([self _savitzkyGolayFilteredZoomFactor], kSCMinVideoZoomFactor, kSCMaxVideoZoomFactor);
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[self _setZoomFactor:filteredZoomFactor forManagedCaptureDevice:device];
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}
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- (CGFloat)_savitzkyGolayFilteredZoomFactor
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{
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if ([_zoomFactorHistoryArray count] == kSCSavitzkyGolayWindowSize) {
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CGFloat filteredZoomFactor =
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59 * [_zoomFactorHistoryArray[4] floatValue] +
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54 * ([_zoomFactorHistoryArray[3] floatValue] + [_zoomFactorHistoryArray[5] floatValue]) +
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39 * ([_zoomFactorHistoryArray[2] floatValue] + [_zoomFactorHistoryArray[6] floatValue]) +
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14 * ([_zoomFactorHistoryArray[1] floatValue] + [_zoomFactorHistoryArray[7] floatValue]) -
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21 * ([_zoomFactorHistoryArray[0] floatValue] + [_zoomFactorHistoryArray[8] floatValue]);
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filteredZoomFactor /= 231;
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return filteredZoomFactor;
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} else {
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return [[_zoomFactorHistoryArray lastObject] floatValue]; // use zoomFactor directly if we have less than 9
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}
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}
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- (void)_resetZoomFactor:(CGFloat)zoomFactor forDevice:(SCManagedCaptureDevice *)device
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{
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[_zoomFactorHistoryArray removeAllObjects];
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[_zoomFactorHistoryArray addObject:@(zoomFactor)];
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[self _setZoomFactor:zoomFactor forManagedCaptureDevice:device];
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}
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@end
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