device.Capture("filename.jpg") creates an invalid file!

Describe the bug

According to the docs here - https://github.com/dotnet/iot/blob/main/src/devices/Media/README.md#videodevice - this should save a jpg to a file:

VideoConnectionSettings settings = new VideoConnectionSettings(busId: 0, captureSize: (2560, 1920), pixelFormat: PixelFormat.YUYV);
using VideoDevice device = VideoDevice.Create(settings);
// Capture static image
device.Capture("/home/pi/jpg_direct_output.jpg");

but the file is created corrupted and/or in wrong format.

Steps to reproduce

just run your code or provide a complete working example.

Versions used

	<PropertyGroup>
		<OutputType>Exe</OutputType>
		<TargetFramework>net6.0</TargetFramework>
		<Platforms>AnyCPU;ARM64</Platforms>
		<LangVersion>Latest</LangVersion>
		<Nullable>enable</Nullable>
		<TreatWarningsAsErrors>true</TreatWarningsAsErrors>
	</PropertyGroup>
...
	<ItemGroup>
		...
		<PackageReference Include="Iot.Device.Bindings" Version="2.0.0" />
		<PackageReference Include="System.Device.Gpio" Version="2.0.0" />
	</ItemGroup>

then I build and publish it to Raspberry Pi 3:

dotnet publish -r linux-arm --self-contained True -c Debug -p:PublishSingleFile=true -p:GenerateRuntimeConfigurationFiles=true

but THIS code works

(all dependencies are installed)

    private void CaptureThePic(CancellationToken cancellationToken)
    {
        /*
         *
         * https://github.com/dotnet/iot/blob/main/src/devices/Media/README.md
         *
         */

        _logger.LogInformation("Capturing the pic...");

        string picName = DateTimeOffset.UtcNow.ToString("s").Replace(":", "");
        string picFileName = $"{PICS_FOLDER_S}/p{picName}.jpg";

        /*
            THIS DOES NOT WORK

            VideoConnectionSettings settings = new(busId: 0, captureSize: (2560, 1920), pixelFormat: PixelFormat.YUYV);
            using VideoDevice device = VideoDevice.Create(settings);
            device.Capture(picFileName);
        */

        VideoConnectionSettings settings = new(0, (1920, 1080), PixelFormat.YUV420);
        using VideoDevice device = VideoDevice.Create(settings);

        // Capture static image
        _logger.LogInformation($"Saving pic as '{picFileName}'...");

        // Get image stream, convert pixel format and save to file
        byte[] imgBytes = device.Capture();
        using MemoryStream ms = new(imgBytes);
        Color[] colors = VideoDevice.Yv12ToRgb(ms, settings.CaptureSize);
        using (Bitmap bitmap = VideoDevice.RgbToBitmap(settings.CaptureSize, colors))
        {
            if (cancellationToken.IsCancellationRequested) return;

            bitmap.Save(picFileName, ImageFormat.Jpeg);
        }

        if (cancellationToken.IsCancellationRequested) return;

        _logger.LogInformation("Saved.\n");
    }

[raffaeler]

Sure @CodedBeard, that would be great. I did not have much time to make other tests today. As soon as we see this compatibility layer working decently, I will make a pull request with this and other changes I already made on my side.

These are the modified PInvokes that I currently declared. All these calls in the bindings should not point to Libc anymore. In the pull request I’ll make sure that this is transparent to the user of course.

    [DllImport("v4l2-compat.so", SetLastError = true)]
    internal static extern int open([MarshalAs(UnmanagedType.LPStr)] string pathname, Interop.FileOpenFlags flags);

    [DllImport("v4l2-compat.so")]
    public static extern int close(int fd);

    [DllImport("v4l2-compat.so", SetLastError = true)]
    public static extern int ioctl(int fd, int request, IntPtr argp);

    [DllImport("v4l2-compat.so", SetLastError = true)]
    public static extern IntPtr mmap(IntPtr addr, int length, MemoryMappedProtections prot, MemoryMappedFlags flags, int fd, int offset);

    [DllImport("v4l2-compat.so")]
    public static extern int munmap(IntPtr addr, int length);

    public enum MemoryMappedProtections
    {
        PROT_NONE = 0x0,
        PROT_READ = 0x1,
        PROT_WRITE = 0x2,
        PROT_EXEC = 0x4
    }

    [Flags]
    public enum MemoryMappedFlags
    {
        MAP_SHARED = 0x01,
        MAP_PRIVATE = 0x02,
        MAP_FIXED = 0x10
    }

[CodedBeard]

@raffaeler cool, as I couldn’t get any of those settings to work either 😃