Function fetchOpenGraphImage

helpers.go:744–787

(ctx context.Context, pageURL *url.URL, imageURLStr string)

			break
		}
	}

	result := openGraphResult{Title: title, Description: description}

	pageURL, err := url.Parse(urlStr)
	if err != nil {
		log.Warn().Err(err).Str("url", urlStr).Msg("Failed to parse page URL for resolving image URL")
		return result
	}

	fetchOpenGraphImage(ctx, pageURL, imageURLStr, &result)
	return result
}

func encodeJPEGThumbnail(img image.Image) []byte {
	var buf bytes.Buffer
	if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: openGraphJpegQuality}); err != nil {
		log.Warn().Err(err).Msg("Failed to encode thumbnail to JPEG")
		return nil
	}
	return buf.Bytes()
}

func fetchOpenGraphImage(ctx context.Context, pageURL *url.URL, imageURLStr string, result *openGraphResult) {
	// No image found on the page; an empty string would resolve to the page
	// URL itself and we would try to decode HTML as an image.
	if imageURLStr == "" {
		return
	}

	imageURL, err := url.Parse(imageURLStr)
	if err != nil {
		log.Warn().Err(err).Str("imageURL", imageURLStr).Msg("Failed to parse Open Graph image URL")
		return
	}

	resolvedImageURL := pageURL.ResolveReference(imageURL).String()
	imgBytes, _, err := fetchURLBytes(ctx, resolvedImageURL, openGraphImageMaxBytes)
	if err != nil {
		log.Warn().Err(err).Str("imageURL", resolvedImageURL).Msg("Failed to fetch Open Graph image")
		return
	}

	imgConfig, _, err := image.DecodeConfig(bytes.NewReader(imgBytes))
	if err != nil {
		log.Warn().Err(err).Str("imageURL", resolvedImageURL).Msg("Failed to decode Open Graph image config")
		return