/
function.go
94 lines (77 loc) · 2.44 KB
/
function.go
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package generatethumbnails
import (
"bytes"
"context"
"fmt"
"image"
"image/jpeg"
"log"
"regexp"
"cloud.google.com/go/storage"
"github.com/disintegration/imaging"
"github.com/pkg/errors"
)
type gcsEvent struct {
Bucket string `json:"bucket"`
ObjectName string `json:"name"`
ContentType string `json:"contentType"`
}
// GenerateThumbnails generates 100px, 500px and 1000px thumbnails for the uploaded image
func GenerateThumbnails(ctx context.Context, e gcsEvent) error {
gcsClient, err := storage.NewClient(ctx)
if err != nil {
log.Fatalf("failed to init storage client: %v", err)
}
if !shouldGenerateThumbnails(e.ObjectName, e.ContentType) {
return nil
}
bucket := gcsClient.Bucket(e.Bucket)
obj := bucket.Object(e.ObjectName)
thumbnailSizes := []int{100, 500, 1000}
for _, size := range thumbnailSizes {
if err := generateResizedImage(ctx, bucket, obj, size, size); err != nil {
return errors.Wrapf(err, "failed to generate thumbnails for %q", e.ObjectName)
}
}
log.Printf("thumbnails for %q have been generated", e.ObjectName)
return nil
}
func generateResizedImage(ctx context.Context, bucket *storage.BucketHandle, originalImage *storage.ObjectHandle, width, height int) error {
reader, err := originalImage.NewReader(ctx)
if err != nil {
return errors.Wrap(err, "failed to read image")
}
objName := fmt.Sprintf("%dx%d@%s", width, height, originalImage.ObjectName())
writer := bucket.Object(objName).NewWriter(ctx)
defer writer.Close()
src, err := imaging.Decode(reader, imaging.AutoOrientation(true))
if err != nil {
return errors.Wrap(err, "failed to decode original image")
}
img := imaging.Thumbnail(src, width, height, imaging.Lanczos)
buff, err := encodeToJpeg(img)
if err != nil {
return errors.Wrapf(err, "failed to encode %dx%d thumbnail image", width, height)
}
if _, err = writer.Write(buff.Bytes()); err != nil {
return errors.Wrap(err, "failed to write resized image")
}
return nil
}
func shouldGenerateThumbnails(fileName string, contentType string) bool {
if !(contentType == "image/jpeg" || contentType == "image/png") {
log.Printf("%q is not image", fileName)
return false
}
resizedImage, _ := regexp.MatchString("^[0-9]+x[0-9]+@", fileName)
if resizedImage {
log.Printf("%q is already resized", fileName)
return false
}
return true
}
func encodeToJpeg(img *image.NRGBA) (*bytes.Buffer, error) {
buff := &bytes.Buffer{}
err := jpeg.Encode(buff, img, nil)
return buff, err
}