feat: limit image resize workers

img/service.go

@@ -0,0 +1,172 @@
+//go:generate go-enum --sql --marshal --file $GOFILE
+package img
+
+import (
+	"context"
+	"errors"
+	"io"
+	"path/filepath"
+
+	"github.com/disintegration/imaging"
+	"github.com/marusama/semaphore/v2"
+	"github.com/spf13/afero"
+)
+
+// ErrUnsupportedFormat means the given image format is not supported.
+var ErrUnsupportedFormat = errors.New("unsupported image format")
+
+// Service
+type Service struct {
+	lowPrioritySem  semaphore.Semaphore
+	highPrioritySem semaphore.Semaphore
+}
+
+func New(workers int) *Service {
+	return &Service{
+		lowPrioritySem:  semaphore.New(workers),
+		highPrioritySem: semaphore.New(workers),
+	}
+}
+
+// Format is an image file format.
+/*
+ENUM(
+jpeg
+png
+gif
+tiff
+bmp
+)
+*/
+type Format int
+
+func (x Format) toImaging() imaging.Format {
+	switch x {
+	case FormatJpeg:
+		return imaging.JPEG
+	case FormatPng:
+		return imaging.PNG
+	case FormatGif:
+		return imaging.GIF
+	case FormatTiff:
+		return imaging.TIFF
+	case FormatBmp:
+		return imaging.BMP
+	default:
+		return imaging.JPEG
+	}
+}
+
+/*
+ENUM(
+high
+medium
+low
+)
+*/
+type Quality int
+
+func (x Quality) resampleFilter() imaging.ResampleFilter {
+	switch x {
+	case QualityHigh:
+		return imaging.Lanczos
+	case QualityMedium:
+		return imaging.Box
+	case QualityLow:
+		return imaging.NearestNeighbor
+	default:
+		return imaging.Linear
+	}
+}
+
+/*
+ENUM(
+fit
+fill
+)
+*/
+type ResizeMode int
+
+func (s *Service) FormatFromExtension(ext string) (Format, error) {
+	format, err := imaging.FormatFromExtension(ext)
+	if err != nil {
+		return -1, ErrUnsupportedFormat
+	}
+	switch format {
+	case imaging.JPEG:
+		return FormatJpeg, nil
+	case imaging.PNG:
+		return FormatPng, nil
+	case imaging.GIF:
+		return FormatGif, nil
+	case imaging.TIFF:
+		return FormatTiff, nil
+	case imaging.BMP:
+		return FormatBmp, nil
+	}
+	return -1, ErrUnsupportedFormat
+}
+
+type resizeConfig struct {
+	prioritized bool
+	resizeMode  ResizeMode
+	quality     Quality
+}
+
+type Option func(*resizeConfig)
+
+func WithMode(mode ResizeMode) Option {
+	return func(config *resizeConfig) {
+		config.resizeMode = mode
+	}
+}
+
+func WithQuality(quality Quality) Option {
+	return func(config *resizeConfig) {
+		config.quality = quality
+	}
+}
+
+func WithHighPriority() Option {
+	return func(config *resizeConfig) {
+		config.prioritized = true
+	}
+}
+
+func (s *Service) Resize(ctx context.Context, file afero.File, width, height int, out io.Writer, options ...Option) error {
+	config := resizeConfig{
+		resizeMode: ResizeModeFit,
+		quality:    QualityMedium,
+	}
+	for _, option := range options {
+		option(&config)
+	}
+
+	sem := s.lowPrioritySem
+	if config.prioritized {
+		sem = s.highPrioritySem
+	}
+
+	if err := sem.Acquire(ctx, 1); err != nil {
+		return err
+	}
+	defer sem.Release(1)
+
+	format, err := s.FormatFromExtension(filepath.Ext(file.Name()))
+	if err != nil {
+		return ErrUnsupportedFormat
+	}
+	img, err := imaging.Decode(file, imaging.AutoOrientation(true))
+	if err != nil {
+		return err
+	}
+
+	switch config.resizeMode {
+	case ResizeModeFill:
+		img = imaging.Fill(img, width, height, imaging.Center, config.quality.resampleFilter())
+	default:
+		img = imaging.Fit(img, width, height, config.quality.resampleFilter())
+	}
+
+	return imaging.Encode(out, img, format.toImaging())
+}