Set every Pixel's Color Component

[brianmed]

I want to set all .A color component of a Rgba32, Bgra32, or Argb32 pixel format image to 255. Is the ProcessPixelRows Api the best way to do this? Considering I want all pixels to have the exact same value, would a custom IPixel class be better?

[antonfirsov]

Considering that your image needs to be fully opaque, can't you use Rgb24 or Bgr24 ? Otherwise ProcessPixelRows is the fastest, while ProcessPixelRowsAsVector4 is a convenient pixel-agnostic way to do it.

[brianmed]

That's a good point about Rgb24 or Bgr24. What I did not articulate is that there is a pipeline. First, we set the .A color component to a known value and then we adjust as needed via Opacity.

[JimBobSquarePants]

I want all pixels to have the exact same value, would a custom IPixel class be better

That wouldn't be useful in your scenario since you have a pipeline and the aforementioned pixel formats do the same thing.

We actually have a processor in the test project that does this operation. This should be fairly efficient (though could be SIMD optimized). I'd just copy that for now.

ImageSharp/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs

Lines 19 to 24 in 4989e14

	/// <summary>
	/// TODO: Consider adding this private processor to the library
	/// </summary>
	/// <param name="ctx">The image processing context.</param>
	public static void MakeOpaque(this IImageProcessingContext ctx) =>
	ctx.ApplyProcessor(new MakeOpaqueProcessor());