[BUG] Huge memory consumption when writing images to PDF

[zenyui]

Description

I am trying to create a PDF from an array of golang image.Image objects. The images are about ~30MB together, and when I write them to the PDF, I observe the docker container spike to 1.4GB memory usage.

In production, this is causing my container to OOM and exit.

See implementation below.

Expected Behavior

I would expect the memory usage to be close to (or 2x, 3x) the size of the images, not 1.4GB! I also don't see a way to incrementally build/finalize the PDF, so I don't see a way to decrease the memory usage.

Actual Behavior

Memory usage is 1.4GB, and I don't see an avenue to accomplish what I'm hoping to do.

Attachments

// pdfFromGoImages creates a pdf from an array of images, each on a separate page
func pdfFromGoImages(ctx context.Context, images ...image.Image) (io.ReadSeeker, error) {
	c := creator.New()

	margins := float64(10)

	for ix, img := range images {
		pImg, err := c.NewImageFromGoImage(img)
		if err != nil {
			return nil, err
		}
		_ = c.NewPage()

		// scale to page width
		pImg.ScaleToWidth(c.Width() - margins*2)
		pImg.SetPos(margins, margins)
		if pImg.Height() >= c.Height() {
			pImg.ScaleToHeight(c.Height() - margins*2)
			pImg.SetPos(margins, margins)
		}
		b := creator.NewBlock(1, 1)
		if err := b.Draw(pImg); err != nil {
			return nil, err
		}
		if err := c.Draw(b); err != nil {
			return nil, err
		}

	}

	var outBytes bytes.Buffer
	writer := bufio.NewWriter(&outBytes)
	if err := c.Write(writer); err != nil {
		return nil, err
	}

	return bytes.NewReader(outBytes.Bytes()), nil
}

[github-actions]

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[zenyui]

FYI, I am a licensed enterprise customer

[sampila]

Hi @zenyui,

Could you share the images that you load into golang image.Image object? so we can reproduce the issue in our ends

[zenyui]

Here is a google drive folder with a few pprof dumps and the source PDF.

The larger algorithm is:

1. extract the images from the source pdf
2. convert to golang image.Image and compress it to 75% quality (attempt to make it smaller)
3. pass into above function to write images to a new PDF

[sampila]

Here is a google drive folder with a few pprof dumps and the source PDF.

The larger algorithm is:

1. extract the images from the source pdf
2. convert to golang image.Image and compress it to 75% quality (attempt to make it smaller)
3. pass into above function to write images to a new PDF

Thanks for the information, we will investigate this issue.

[zenyui]

Still waiting on a solution.

[ipod4g]

@zenyui
We have already improved partly PDF creation from images and introduced lazy mode allowing us to reduce memory consumption.
you can check it here:
https://github.com/unidoc/unipdf-examples/blob/master/image/pdf_images_to_pdf_lazy.go

As for image extraction, we are actively working on that and and we will keep you updated on our progress.