Transparent Linear Gradient

[stevetayloruk]

Hi,

I'm trying to add a linear gradient the starts solid and fades to transparent over the top of an existing image but can't seem to achieve the transparancy aspect of it.

Before:

After:

I'm using the LinearGradientBrush and the code works with two solid colours, but I can't seem to get the transparancy working.

TIA

[JimBobSquarePants]

Without any code it’s hard to say what you are doing wrong. My guess is though that you’re using a pixel format that does not support alpha transparency.

[stevetayloruk]

Here is the code I'm using. The transparency comes out as black

public FormattedImage Process(FormattedImage image, ILogger logger, CommandCollection commands, CommandParser parser, CultureInfo culture)
  {
    var extension = commands.GetValueOrDefault(Logo);

    if (!string.IsNullOrEmpty(extension))
    {
      var linearGradientBrush = new LinearGradientBrush(new Point(0, 0), new Point(0, 100), GradientRepetitionMode.DontFill, new ColorStop(0, Color.Black), new ColorStop(1, Color.Transparent));

      image.Image.Mutate(x =>  { 
        x.Fill(linearGradientBrush);
      }   
    );
    }

    return image;
  }

Thanks for helping.

[stevetayloruk]

Yes, the latest version. 2.0.2

    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.3" />
    <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="1.0.0-beta15" />
    <PackageReference Include="SixLabors.ImageSharp.Web" Version="2.0.2" />
    <PackageReference Include="SixLabors.ImageSharp.Web.Providers.Azure" Version="2.0.2" />

[JimBobSquarePants]

What's the value of IImageWebProcessor.RequiresAlphaAwarePixelFormat?

[stevetayloruk]

Sorry, I can't seem to find this property on IImageWebProcessor and can't see it referenced in the documentation either. The interface only seems to have RequiresTrueColorPixelFormat

[JimBobSquarePants]

Ah yes, I forgot I updated that before release.

That property needs to return true so that the pipeline knows we require a 32-bit True Color pixel format pixel format (8 bits per color component plus an 8-bit alpha channel). You could be smart about it and only return true if your linear gradient contains a transparent color.

[stevetayloruk]

Thanks! yes that did the trick.

Appreciate the help.