Can't get TIFF compression to work

[Tom-EllisEVENTS]

I'm trying to convert PDF to multi-page TIFF and can't get the compression working.

Currently, my code looks like this:

    using (var images = new MagickImageCollection())
    {
        // Add all the pages of the pdf file to the collection
        images.Read(e.FullPath, settings);

        using (var tif = new MagickImageCollection())
        {
            var page = 1;
            foreach (var image in images)
            {
                Console.WriteLine("converting page " + page);
                image.Format = MagickFormat.Tiff;
                image.SetCompression(CompressionMethod.LZW);
                tif.Add(image);

                page++;
            }

            tif.Write(e.Name + ".tif", MagickFormat.Tiff);

        }
    }

But when looking at the resulting file with IrfanView, it tells me that the file is uncompressed - a 7 page PDF with 170 KB size is inflated to a 250 MB TIF file with 300 dpi density settings.

I thought "image.setCompression(...)" should do the trick... Apparently, this seems to be a recurring topic :-)

Using Magick.NET Version 9.1.2

[dlemstra]

Can you share your input file? The initial size does not mean anything because the image is a vector image and when it is read with ImageMagick it will be changed to a raster image.

[Tom-EllisEVENTS]

See attached ZIP file with the PDF and TIF file.

But I don't think the point is the actual file, because if I save the tiff file from IrfanView with LZW compression, it shrinks to a few 100 kb.

It seems like the SetCompression call is just ineffective.

While debugging, one thing caught my attention:

The compression attribute of each image in the "tif" collection is set to "LZW", but not _settings.compression, which is "undefined"

Lorem ipsum dolor sit amet.pdf.zip

[dlemstra]

You should not call SetCompression but set the compression of the first image in the collection instead.

using (var images = new MagickImageCollection())
{
    images.Read("Lorem ipsum dolor sit amet.pdf", new MagickReadSettings
    {
        Density = new Density(150),
    });

    images[0].Settings.Compression = CompressionMethod.LZW;

    images.Write("test.tif");
}

[Tom-EllisEVENTS]

It works, but does this make sense...?

What is the reason that SetCompression() does not set Settings.Compression as well?

This is not very intuitive...

[dlemstra]

I agree that it isn't and that is why that method has the following comment:

Gets the compression of the image. This method should only be used when the encoder uses the compression of the image. For most usecases Setting.Compression should be used instead.