Access to pointer position in image pixel coordinates through a property

[parandyk]

Hey, I started using UVtools Avalonia custom controls a while ago and it's really great; the AdvancedImageBox feels like a whole app in and of itself.

Anyway, I thought adding a property for easy access to image pixel coordinates of the pointer could be useful - the methods for it are all there already (the PointToImage method). If I reckon correctly, this would entail just adding a new property and tracking the changes along the original PointerPosition in ViewPortOnPointerMoved method.

[sn4k3]

Extra property will cause a extra calls and executions.
As I understand you want a property that reflects:

Point currentPixel = PointToImage(PointerPosition);

If that right, can you tell me the use case / benefit?
Because same can be obtained by subscribe to PointerPosition and then calculate it as: Point currentPixel = PointToImage(PointerPosition);

[parandyk]

Sadly not, at least not in the raw form - it changes if the image is panned or zoomed, and it shouldn't. I did get the expected outcome with a custom behavior though, here's the code:

using System;
using System.Windows.Input;
using Avalonia.Xaml.Interactivity;
using Avalonia;
using UVtools.AvaloniaControls;

namespace ImageAnnotationTool.Behaviors;

public class InvokeImageCoordinateAction : AvaloniaObject, IAction
{
    public static readonly StyledProperty<ICommand?> CommandProperty =
        AvaloniaProperty.Register<InvokeImageCoordinateAction, ICommand?>(
            nameof(Command));
    
    public ICommand? Command
    {
        get => GetValue(CommandProperty);
        set => SetValue(CommandProperty, value);
    }

    public object? Execute(object? sender, object? parameter)
    {
        if (sender is not AdvancedImageBox imgBox || Command is null)
        {
            return null;
        }

        var pointer = imgBox.PointerPosition;
        var pixel = imgBox.PointToImage(pointer);

        var outputTuple = new Tuple<Point, Point>(pointer, pixel);
        
        if (Command.CanExecute(outputTuple))
            Command.Execute(outputTuple);

        return outputTuple;
    }
}

Right now I'm trying to get the boxes drawn nicely, as the panning and zooming only affects the AdvancedImageBox itself.

[sn4k3]

So you want to select region while pan and/or zoom right?
I don't mind exposing the ViewPort if you need it.

[parandyk]

Yes, that would be ideal as it would allow for easy conversion of coordinates.

[sn4k3]

Ok, in meantime I think you can use the imagebox itself, as viewport fill the imagebox without margin, the coordinates should be the same

[parandyk]

Of course, this isn't anything I desperately need ASAP. Thanks!