Tiled checkerboard behind image with transparency

[simonmurdock]

I understand IM has this built in via some pattern parameter, but I do not know how to pass this in via Magick.NET.

Or even a way to specify my own checkerboard pattern as a jpg and tile it?

Could you possibly assist? :)

[dlemstra]

Do you know the command line variant of what you are trying to achieve? Do you want to draw an image over a tiled checkerboard background like Photoshop does?

[simonmurdock]

I tried some command line variants but had trouble getting those to work how I wanted.

But yes, I want to replicate the photoshop effect where the checkerboard is shown below the transparent areas of the image provided. in this case a .png file. But using my own image for the checkerboard, a 16x16 png file.

The reason I need this is because our gallery web page has a white background, and one client is uploading white logos with a transparent background, making their thumbnails appear invisible.

Thank you

[dlemstra]

You could also use the MagickImage.ColorAlpha method for and use a color instead of a pattern. But I think you would want to use the Tile method. Your first action has to be to extend the image to as size that it won't show 'half' of your pattern. A 30x20 image would become 32x32 in your case (16x16 pattern). And then you can use the following method logo.Tile(pattern, CompositeOperator.??) I am not sure which operator you would need, prob SrcOver or DstOver.

[simonmurdock]

I think i was using DstOver in my previous exmaples.

I will give that a go, thanks

update:

Here was the code I used:

using (var image = new MagickImage())
{
    image.Read(Files.GetPath(file), settings);

    using (var checkerBoardImage = new MagickImage())
    {
        checkerBoardImage.Read(CheckerboardPath);
        image.BackgroundColor = MagickColor.Transparent;
        image.Tile(checkerBoardImage, CompositeOperator.DstOver);
    }
    image.Write(path); 
}

[simonmurdock]

Just For my information - is there a methodology to how the API is laid out for Magick.net? Because I can often find a raw imageMagick commandline for what I want to do, but find it very difficult to convert that to a Magick.Net way.

Would it be possible to get some documentation?

[dlemstra]

Most command line options are methods/properties on the MagickImage class. There are some examples available here: https://magick.codeplex.com/documentation but I agree with you that this project needs more and better documentation. I don't have/make enough time for that.

[simonmurdock]

ah okay, I might have a go some day
thank you for your help! working nicely.