In MewUI, what is the best way to create images directly from RGBA data?

[harry-xi]

ImageSource always require an encoded byte as its input. but in many case I may have image data in an decoded way. How should I do that?

When I try to implement the IImageSource, I found I should pass a IPixelBufferSource into CreateImageView to get an image, the I found out that StaticPixelBufferSource is an wonderful implement of IPixelBufferSource for my need, but it is an internal class so I can't use it. So, what should I do?

[al6uiz]

Thanks for the feedback!

In the upcoming release, I plan to expose many classes that are currently internal as public APIs. This will not be completed in a single short-term change, though. I would like to refine the public API surface gradually while collecting more feedback and real use cases.

StaticPixelBufferSource may be one such candidate.

However, I still need to decide whether it should be exposed directly, or whether this should be handled through a factory API or a separate image/pixel-buffer system with clearer BGRA/RGBA interop.

Creating images directly from decoded pixel data is a valid use case, and I will consider this while refining the public image-related APIs.

[al6uiz]

I added a new raw-pixel path for this case in ImageSource.FromBgraPixels:

MewUI/src/MewUI/Resources/ImageSource.cs

Lines 162 to 190 in 48de17f

	public static ImageSource FromBgraPixels(int width, int height, byte[] bgra, bool hasAlpha = true)
	{
	ArgumentNullException.ThrowIfNull(bgra);
	return new(new Bgra32PixelBuffer(width, height, bgra, hasAlpha));
	}
	/// <summary>
	/// Copies BGRA32 pixels into a new buffer.
	/// </summary>
	public static ImageSource FromBgraPixels(int width, int height, ReadOnlySpan<byte> bgra, bool hasAlpha = true)
	{
	if (width <= 0 || height <= 0)
	{
	throw new ArgumentOutOfRangeException(nameof(width), "Dimensions must be positive.");
	}
	int expected = checked(width * height * 4);
	if (bgra.Length != expected)
	{
	throw new ArgumentException($"Expected {expected} bytes (tight-packed BGRA32), got {bgra.Length}.", nameof(bgra));
	}
	var copy = GC.AllocateUninitializedArray<byte>(expected);
	bgra.CopyTo(copy);
	return new(new Bgra32PixelBuffer(width, height, copy, hasAlpha));
	}
	/// <summary>
	/// Wraps an existing <see cref="Bgra32PixelBuffer"/>. The buffer's array is referenced (not copied).
	/// </summary>
	public static ImageSource FromBgraPixels(Bgra32PixelBuffer buffer) => new(buffer);

var image = ImageSource.FromBgraPixels(width, height, bgra);

MewUI now allows ImageSource to be created directly from BGRA32 pixel data without going through an encoded image format.

The API is BGRA-based because MewUI internally treats decoded image data as BGRA32. This also matches the common native pixel layout used by many graphics APIs and backends.

If your source data is RGBA, you can convert it to MewUI's BGRA layout first by using PixelFormatConverter.FromRgba:

MewUI/src/MewUI/Resources/PixelFormatConverter.cs

Lines 20 to 35 in 98b14ae

	public static Bgra32PixelBuffer FromRgba(int width, int height, ReadOnlySpan<byte> rgba, bool hasAlpha = true)
	{
	if (width <= 0 || height <= 0)
	{
	throw new ArgumentOutOfRangeException(nameof(width), "Dimensions must be positive.");
	}
	int expected = checked(width * height * 4);
	if (rgba.Length != expected)
	{
	throw new ArgumentException($"Expected {expected} bytes (tight-packed RGBA32), got {rgba.Length}.", nameof(rgba));
	}
	var bgra = GC.AllocateUninitializedArray<byte>(expected);
	SimdDispatcher.SwapRedBlue32(rgba, bgra);
	return new Bgra32PixelBuffer(width, height, bgra, hasAlpha);
	}

var buffer = PixelFormatConverter.FromRgba(width, height, rgba);
var image = ImageSource.FromBgraPixels(buffer);

The change was added in this commit:

b813d4b