Documentation for ImageProcessing::Builder?

[brian-nicholls]

I am using CarrierWave::MiniMagick. According to the docs:

"...create your own helpers with the powerful minimagick! method, which yields an ImageProcessing::Builder object."

However I don't see any mention here in the docs of how to use the Builder object. I am trying to composite a PNG watermark onto a PDF.

For reference, the below code using manipulate! works on my local environment, but not on the Dockerized production environment. Since the docs say it only exists for backwards compatibility, I am trying to get it working using minimagick! via this gem. Any chance someone could help with translating this into a version using ImageProcessing::Builder?

      manipulate! do |source_pdf|
        watermark_image = MiniMagick::Image.open("#{Rails.root}/app/assets/images/watermark.png")
        source_pdf.composite(watermark_image) do |c|
          c.compose 'overlay'
          c.tile
        end
      end

Thanks for any help!

[janko]

Anything you see in the MiniMagick backend docs can be called on the ImageProcessing::Builder option. It's just an object that supports chaining, similarly to ActiveRecord::Relation.

The following should work:

minimagick! do |builder|
  watermark_path = "#{Rails.root}/app/assets/images/watermark.png"
  builder.composite(watermark_path, mode: "overlay") do |c|
    c.tile
  end
end

[brian-nicholls]

Thanks for the quick reply! Unfortunately using the above I am seeing this:

CarrierWave::ProcessingError (Failed to manipulate with MiniMagick, maybe it is not an image? Original Error: `convert /workspaces/mf_api_server/tmp/1668644236-329297852097376-0005-5183/watermarked/dp_1461_1668644236776.pdf -auto-orient /workspaces/mf_api_server/app/assets/images/watermark.png -compose overlay -tile -composite /tmp/image_processing20221117-18068-1an7xtm.pdf` failed with error:
convert-im6.q16: unable to open image `-composite': No such file or directory @ error/blob.c/OpenBlob/2924.
convert-im6.q16: no decode delegate for this image format `' @ error/constitute.c/ReadImage/575.
):

I've seen this error happening using different methods, even when the extension is clearly PDF and should be a supported image. I've checked the delegates file, which does include PDF. I'm stumped, and probably going to have to use a different method using the HexaPDF gem :(

[janko]

It doesn't seem the problem is PDF, it's interpreting something else as an image; it says no decode delegate for this image format '', and we see the actual format is missing. Are you sure the -tile is valid here? If it is, doesn't -tile expect an argument? I think that might be tripping ImageMagick up.

[brian-nicholls]

I also tried omitting the tile but wound up with a similar error:

      minimagick! do |builder|
        watermark_path = "#{Rails.root}/app/assets/images/watermark.png"
        builder.composite(watermark_path, mode: "overlay")
      end

Gives me

CarrierWave::ProcessingError (Failed to manipulate with MiniMagick, maybe it is not an image? Original Error: `convert /workspaces/mf_api_server/tmp/1668696818-126439900497953-0003-9055/watermarked/dp_1484_1668696818715.pdf -auto-orient /workspaces/mf_api_server/app/assets/images/watermark.png -compose overlay -composite /tmp/image_processing20221117-14443-t7rvs9.pdf` failed with error:
convert-im6.q16: image sequence is required `-composite' @ error/mogrify.c/MogrifyImageList/7987.
convert-im6.q16: no images defined `/tmp/image_processing20221117-14443-t7rvs9.pdf' @ error/convert.c/ConvertImageCommand/3229.
):

And explicitly returning the builder, gives me another version of the error:

      minimagick! do |builder|
        watermark_path = "#{Rails.root}/app/assets/images/watermark.png"
        builder.composite(watermark_path, mode: "overlay")
        builder
      end

CarrierWave::ProcessingError (Failed to manipulate with MiniMagick, maybe it is not an image? Original Error: `convert /workspaces/mf_api_server/tmp/1668697249-551170488041120-0008-3457/watermarked/dp_1489_1668697249843.pdf -auto-orient /tmp/image_processing20221117-14443-1ji0c4p.pdf` failed with error:
convert-im6.q16: no images defined `/tmp/image_processing20221117-14443-1ji0c4p.pdf' @ error/convert.c/ConvertImageCommand/3229.
):

What bugs me is that it works perfectly fine on my development environment, but not on the Dockerized staging environment. Because of this I'm convinced it has to have something to do with the filesystem - I can't think of any other difference.