// ServeArt provides a common method for serving and resizing Art, based on
// an input HTTP request.
func ServeArt(w http.ResponseWriter, r *http.Request, art *data.Art) error {
// Attempt to access art data stream
stream, err := art.Stream()
if err != nil {
return err
}
// Check for resize request, if none, serve directly
size := r.URL.Query().Get("size")
if size == "" {
// Serve content directly, account for range headers, and enabling caching.
http.ServeContent(w, r, art.FileName, time.Unix(art.LastModified, 0), stream)
return nil
}
// Ensure size is a valid integer
sizeInt, err := strconv.Atoi(size)
if err != nil {
return ErrInvalidIntegerSize
}
// Verify positive integer
if sizeInt < 1 {
return ErrNegativeIntegerSize
}
// Decode input image stream
img, imgFormat, err := image.Decode(stream)
if err != nil {
return err
}
// Generate a thumbnail image of the specified size
img = resize.Resize(uint(sizeInt), 0, img, resize.NearestNeighbor)
// Encode to original format for output
buffer := bytes.NewBuffer(nil)
if imgFormat == "jpeg" {
// JPEG, lossy encoding, default quality
if err := jpeg.Encode(buffer, img, nil); err != nil {
return err
}
} else {
// Always send PNG as a backup
// PNG, lossless encoding
if err := png.Encode(buffer, img); err != nil {
return err
}
}
// Serve content directly, account for range headers, and enabling caching.
http.ServeContent(w, r, art.FileName, time.Unix(art.LastModified, 0), bytes.NewReader(buffer.Bytes()))
return nil
}
