Function createPreview

http/preview.go:113–153

(imgSvc ImgService, fileCache FileCache,
	file *files.FileInfo, previewSize PreviewSize)

}

func createPreview(imgSvc ImgService, fileCache FileCache,
	file *files.FileInfo, previewSize PreviewSize) ([]byte, error) {
	fd, err := file.Fs.Open(file.Path)
	if err != nil {
		return nil, err
	}
	defer fd.Close()

	var (
		width   int
		height  int
		options []img.Option
	)

	switch previewSize {
	case PreviewSizeBig:
		width = 1080
		height = 1080
		options = append(options, img.WithMode(img.ResizeModeFit), img.WithQuality(img.QualityMedium))
	case PreviewSizeThumb:
		width = 256
		height = 256
		options = append(options, img.WithMode(img.ResizeModeFill), img.WithQuality(img.QualityLow), img.WithFormat(img.FormatJpeg))
	default:
		return nil, img.ErrUnsupportedFormat
	}

	buf := &bytes.Buffer{}
	if err := imgSvc.Resize(context.Background(), fd, width, height, buf, options...); err != nil {
		return nil, err
	}

	go func() {
		cacheKey := previewCacheKey(file, previewSize)
		if err := fileCache.Store(context.Background(), cacheKey, buf.Bytes()); err != nil {
			fmt.Printf("failed to cache resized image: %v", err)
		}
	}()

	return buf.Bytes(), nil
}

func previewCacheKey(f *files.FileInfo, previewSize PreviewSize) string {
	return fmt.Sprintf("%x%x%x", f.RealPath(), f.ModTime.Unix(), previewSize)