How to apply a mask with transparent background?

[TheColorRed]

I am trying to take an image and fade the edges. What I have done is created an elliptical gradient (black in the center and white on the edges). I have tried many things nothing seems to be working. I was able to get this once but it was on the image layer and not the one that I wanted it on causing issues.

The below creates a 100% transparent image and places it on the final image so basically the image disappears. I have tried using White for the maskedImage, but that leaves an image with a white edge and not a transparent one.

var image = new MagickImage("images/background.png");
var boat = new MagickImage("images/boat.png");
var mask = new MagickImage("images/mask.png");

// Create the masked image
var maskedImage = new MagickImage(MagickColors.Transparent, boat.Width, boat.Height);
maskedImage.SetWriteMask(mask);
maskedImage.Composite(boat, Channels.RGB | Channels.Alpha);

// I have tried removing the mask at this point

// Add the masked image to the final image
image.Composite(maskedImage, Gravity.Center, CompositeOperator.Overlay, Channels.RGB);

// I have tried removing the mask at this point

image.Write("out.png");

background.png

boat.png

mask.png

[dlemstra]

Have you tried removing the write mask from layerImage? And is it possible to make your code sample smaller and include some test images?

[TheColorRed]

That looks like it does what I am looking for! Thanks!

[TheColorRed]

Is there anyway for this to work with a Transparent root image? This gives me a blank image...

var image = new MagickImage(MagickColors.Transparent, 800, 600);
var boat = new MagickImage("images/boat.png");
var mask = new MagickImage("images/mask.png");

mask.Extent(image.Width, image.Height, Gravity.Center);

image.SetWriteMask(mask);

image.Composite(boat, Gravity.Center, Channels.RGB | Channels.Alpha);

image.Write("out.png");

[dlemstra]

You will need a slightly different approach for that:

image.Composite(boat, Gravity.Center, CompositeOperator.Over);

mask.Extent(image.Width, image.Height, Gravity.Center);
mask.Negate();

image.Composite(mask, CompositeOperator.CopyAlpha);

[TheColorRed]

After a few hours of trial and error of it working in my testing environment and not in my actual application, I noticed that it wasn't working in my application when using the following to generate a gradient mask.

var start = MagickColors.Black.ToString();
var end = MagickColors.White.ToString();
var readSettings = new MagickReadSettings {
  Width = boat.Width,
  Height = boat.Height
};

readSettings.SetDefine("gradient:extent", "ellipse");
var mask = new MagickImage($"radial-gradient:{start}-{end}", readSettings);

When Negate() is run, the mask is converted to complete transparency along with the boat. When I don't Negate() the boat is 100% opaque.

I have tried many different settings on the gradient, but none of them work. Visually the gradient is created properly.

Note: The radial image I supplied in the OP was generated with the gimp, and that image works.

[TheColorRed]

I got it, just needed to turn off the alpha. Thanks for the help!

mask.Alpha(AlphaOption.Off);
mask.Negate();