Skip to content

Commit

Permalink
Merge pull request #127 from karolbielski/bugfix/issue-124-113-89
Browse files Browse the repository at this point in the history
[#89] [#113] [#124] Focus improvements on dual and tripple cameras
  • Loading branch information
nathanfallet authored Feb 23, 2024
2 parents bf5d708 + a9dc96a commit 7da6b1e
Show file tree
Hide file tree
Showing 2 changed files with 144 additions and 0 deletions.
19 changes: 19 additions & 0 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ You can provide a variety of extra customization options to `CodeScannerView` in
- `showViewfinder` determines whether to show a box-like viewfinder over the UI. Default: false.
- `simulatedData` allows you to provide some test data to use in Simulator, when real scanning isn’t available. Default: an empty string.
- `shouldVibrateOnSuccess` allows you to determine whether device should vibrate when a code is found. Default: true.
- `videoCaptureDevice` allows you to choose different capture device that is most suitable for code to scan.

If you want to add UI customization, such as a dedicated Cancel button, you should wrap your `CodeScannerView` instance in a `NavigationView` and use a `toolbar()` modifier to add whatever buttons you want.

Expand Down Expand Up @@ -87,6 +88,24 @@ struct QRCodeScannerExampleView: View {
}
```

## Scanning small QR codes

Scanning small QR code on devices with dual or tripple cameras has to be adjusted because of minimum focus distance built in these cameras.
To have the best possible focus on the code we scan it is needed to choose the most suitable camera and apply recommended zoom factor.

Example for scanning 20x20mm QR codes.

```swift
CodeScannerView(codeTypes: [.qr], videoCaptureDevice: AVCaptureDevice.zoomedCameraForQRCode(withMinimumCodeSize: 20)) { response in
switch response {
case .success(let result):
print("Found code: \(result.string)")
case .failure(let error):
print(error.localizedDescription)
}
}
```


## Credits

Expand Down
125 changes: 125 additions & 0 deletions Sources/CodeScanner/AVCaptureDevice+bestForBuiltInCamera.swift
Original file line number Diff line number Diff line change
@@ -0,0 +1,125 @@
//
// AVCaptureDevice+bestForBuiltInCamera.swift
// https://github.com/twostraws/CodeScanner
//
// Created by Karol Bielski on 10/02/2024.
// Copyright © 2024 Paul Hudson. All rights reserved.
//

import AVFoundation

@available(macCatalyst 14.0, *)
extension AVCaptureDevice {

/// Returns best built in back camera for scanning QR codes zoomed for a given minimum code size.
static func zoomedCameraForQRCode(withMinimumCodeSize minimumCodeSize: Float = 20) -> AVCaptureDevice? {
let captureDevice = AVCaptureDevice.DiscoverySession(
deviceTypes: [.builtInWideAngleCamera],
mediaType: .video,
position: .back
).devices.first ?? AVCaptureDevice.default(for: .video)

if #available(iOS 15.0, *) {
captureDevice?.setRecommendedZoomFactor(forMinimumCodeSize: minimumCodeSize)
}

return captureDevice
}

/// Sets recommended zoom factor for a given minimum code size.
@available(iOS 15.0, *)
func setRecommendedZoomFactor(forMinimumCodeSize minimumCodeSize: Float) {
/*
Optimize the user experience for scanning QR codes down to given size.
When scanning a QR code of that size, the user may need to get closer than
the camera's minimum focus distance to fill the rect of interest.
To have the QR code both fill the rect and still be in focus, we may need to apply some zoom.
*/
let deviceMinimumFocusDistance = Float(minimumFocusDistance)
guard deviceMinimumFocusDistance != -1 else { return }

let deviceFieldOfView = activeFormat.videoFieldOfView
let formatDimensions = CMVideoFormatDescriptionGetDimensions(activeFormat.formatDescription)
let rectOfInterestWidth = Double(formatDimensions.height) / Double(formatDimensions.width)
let minimumSubjectDistanceForCode = minimumSubjectDistanceForCode(
fieldOfView: deviceFieldOfView,
minimumCodeSize: minimumCodeSize,
previewFillPercentage: Float(rectOfInterestWidth)
)

guard minimumSubjectDistanceForCode < deviceMinimumFocusDistance else { return }

let zoomFactor = deviceMinimumFocusDistance / minimumSubjectDistanceForCode
do {
try lockForConfiguration()
videoZoomFactor = CGFloat(zoomFactor)
unlockForConfiguration()
} catch {
print("Could not lock for configuration: \(error)")
}
}

private func minimumSubjectDistanceForCode(
fieldOfView: Float,
minimumCodeSize: Float,
previewFillPercentage: Float
) -> Float {
/*
Given the camera horizontal field of view, we can compute the distance (mm) to make a code
of minimumCodeSize (mm) fill the previewFillPercentage.
*/
let radians = (fieldOfView / 2).radians
let filledCodeSize = minimumCodeSize / previewFillPercentage
return filledCodeSize / tan(radians)
}
}

private extension Float {
var radians: Float {
self * Float.pi / 180
}
}

/*
Part of this code is copied from Apple sample project "AVCamBarcode: Using AVFoundation to capture barcodes".
IMPORTANT: This Apple software is supplied to you by Apple
Inc. ("Apple") in consideration of your agreement to the following
terms, and your use, installation, modification or redistribution of
this Apple software constitutes acceptance of these terms. If you do
not agree with these terms, please do not use, install, modify or
redistribute this Apple software.
In consideration of your agreement to abide by the following terms, and
subject to these terms, Apple grants you a personal, non-exclusive
license, under Apple's copyrights in this original Apple software (the
"Apple Software"), to use, reproduce, modify and redistribute the Apple
Software, with or without modifications, in source and/or binary forms;
provided that if you redistribute the Apple Software in its entirety and
without modifications, you must retain this notice and the following
text and disclaimers in all such redistributions of the Apple Software.
Neither the name, trademarks, service marks or logos of Apple Inc. may
be used to endorse or promote products derived from the Apple Software
without specific prior written permission from Apple. Except as
expressly stated in this notice, no other rights or licenses, express or
implied, are granted by Apple herein, including but not limited to any
patent rights that may be infringed by your derivative works or by other
works in which the Apple Software may be incorporated.
The Apple Software is provided by Apple on an "AS IS" basis. APPLE
MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND
OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.
IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL
OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION,
MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED
AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE),
STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
Copyright (C) 2016 Apple Inc. All Rights Reserved.
*/

0 comments on commit 7da6b1e

Please sign in to comment.