I'm writing an app to help with astrophotography, and I need to perform a contrast stretch to the image, because it was taken with a specialized astrophotography camera in monochrome and most of the data is very dark. Most astrophotography software (astropy, Pixinsight) has something called an autostretch, which is a form of contrast stretching. I would like to do the same thing in my iOS app, using the tools available to me in SwiftUI, UIImage, CIImage, and CGImage. I am to the point that I have created a buffer .withUnsafeMutableBufferPointer that contains the image data as 16-bit unsigned integers (the format given to me by the camera). I then create a vImage_Buffer using: var buffer = vImage_Buffer(data: outPtr.baseAddress, height: vImagePixelCount(imageHeight), width: vImagePixelCount(imageWidth), rowBytes: MemoryLayout<Float>.size * imageWidth) ... and now I would like to apply either an equalizeHistogram() or a contrastStretch() to the buffer. What do I need to do? Do I need to create a CGImageFormat, like this? let cgiImageFormat = vImage_CGImageFormat(bitsPerComponent: 16, bitsPerPixel: 16, colorSpace: CGColorSpaceCreateDeviceGray(), bitmapInfo: bitmapInfo)! Which function should I use to do the equalization or contrast stretch? There appears to be a vImageContrastStretch_PlanarF() function, but I'm not sure the input data will be in the proper format (is a monochrome CGImage 32-bit planar F?), and I certainly don't know how to setup the histogram_entries parameter for that function. It seems like the function could just scan the image itself, form the histogram, and then stretch it, right? So a code example would help a lot! Thanks in advance, Robert

I have an app that is communicating with a non-HTTP server over TCP/IP. Most everything is working, but I was testing some error conditions and the first one I tried was turning the server off and then trying to send it a message. I'm using code that uses NWConnection and involves an async method that includes a withCheckedContinuation. Inside this code are checks for errors in the closures, etc. You've seen the example code posted here in the forums. But none of the error code ever gets invoked. I also have a state handler to check the state of the TCP connection. What I see when I send the request is: connection goes to .preparing state nothing happens for about 45 seconds I then get two errors: inline-code nw_endpoint_flow_failed_with_error [C4.1.1 192.168.86.44:3040 in_progress channel-flow (satisfied (Path is satisfied), viable, interface: en0[802.11], ipv4, dns, uses wifi)] already failing, returning inline-code nw_endpoint_flow_failed_with_error [C4.1.1 192.168.86.44:3040 cancelled channel-flow ((null))] already failing, returning then the connection state goes to .waiting and nothing else happens. I would really like to capture the errors I see in the Xcode console, but I don't know how to catch them. Anyone have any ideas? Is there a better way to send the first message (or a ping or whatever) to a non-HTTP server and see if it is there? Thanks, Robert

This is obviously a user error, but I've been working on different possibilities for a couple of days and nothing works. The problem is my Section in the following code doesn't expand or collapse when I click on the chevron: `class AstroCat { var title: String var contents: [ String ] var isExpanded: Bool init(title: String, contents: [String], isExpanded: Bool) { self.title = title self.contents = contents self.isExpanded = isExpanded } } struct TestView: View { @Binding var isShowingTargetSelection: Bool @State var catalog: AstroCat @State private var expanded = false var body: some View { NavigationStack { List { Section(catalog.title, isExpanded: $catalog.isExpanded) { ForEach(catalog.contents, id: \.self) { object in Text(object) } } } .navigationTitle("Target") .listStyle(.sidebar) } } } #Preview { struct TestPreviewContainer : View { @State private var value = false @State var catalog = AstroCat(title: "Solar System", contents: ["Sun", "Mercury", "Venus", "Earth"], isExpanded: true) var body: some View { TestView(isShowingTargetSelection: $value, catalog: catalog) } } return TestPreviewContainer() }` If I change the "isExpanded: $catalog.isExpanded" to just use the local variable "expanded", then it works, so I think I have the basic SwiftUI pieces correct. But using a boolean inside of the class doesn't seem to work (the section just remains expanded or collapsed based on the initial value of the class variable). Any hints? Am I not specifying the binding correctly? (I've tried a bunch of alternatives) Thanks for the help, Robert