GZip compression support

README.md

@@ -14,6 +14,7 @@ Imgproxy is 12factor-ready and can be configured with env variables:
 * IMGPROXY_MAX_SRC_DIMENSION - the maximum dimension of source image. Images with larger size will be rejected. Default: 4096;
 * IMGPROXY_QUALITY - quality of a result image. Default: 80;
 * IMGPROXY_COMPRESSION - compression of a result image. Default: 6;
+* IMGPROXY_COMPRESSION - GZip compression level. Default: 5;
 * IMGPROXY_KEY - hex-encoded key
 * IMGPROXY_SALT - hex-encoded salt
 

config.go

@@ -80,8 +80,9 @@ type config struct {
 
 	MaxSrcDimension int
 
-	Quality     int
-	Compression int
+	Quality         int
+	Compression     int
+	GZipCompression int
 
 	Key  []byte
 	Salt []byte
@@ -94,6 +95,7 @@ var conf = config{
 	MaxSrcDimension: 4096,
 	Quality:         80,
 	Compression:     6,
+	GZipCompression: 5,
 }
 
 func init() {
@@ -109,6 +111,7 @@ func init() {
 
 	intEnvConfig(&conf.Quality, "IMGPROXY_QUALITY")
 	intEnvConfig(&conf.Compression, "IMGPROXY_COMPRESSION")
+	intEnvConfig(&conf.GZipCompression, "IMGPROXY_GZIP_COMPRESSION")
 
 	hexEnvConfig(&conf.Key, "IMGPROXY_KEY")
 	hexEnvConfig(&conf.Salt, "IMGPROXY_SALT")

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"compress/gzip"
 	"encoding/base64"
 	"errors"
 	"fmt"
@@ -88,12 +89,25 @@ func logResponse(status int, msg string) {
 	log.Printf("|\033[7;%dm %d \033[0m| %s\n", color, status, msg)
 }
 
-func respondWithImage(rw http.ResponseWriter, data []byte, imgURL string, po processingOptions) {
+func respondWithImage(r *http.Request, rw http.ResponseWriter, data []byte, imgURL string, po processingOptions) {
 	logResponse(200, fmt.Sprintf("Processed: %s; %+v", imgURL, po))
 
-	rw.WriteHeader(200)
+	gzipped := strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") && conf.GZipCompression > 0
+
 	rw.Header().Set("Content-Type", imageContentType(data))
-	rw.Write(data)
+	if gzipped {
+		rw.Header().Set("Content-Encoding", "gzip")
+	}
+
+	rw.WriteHeader(200)
+
+	if gzipped {
+		gz, _ := gzip.NewWriterLevel(rw, conf.GZipCompression)
+		gz.Write(data)
+		gz.Close()
+	} else {
+		rw.Write(data)
+	}
 }
 
 func respondWithError(rw http.ResponseWriter, status int, err error, msg string) {
@@ -129,7 +143,7 @@ func (h httpHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	respondWithImage(rw, b, imgURL, procOpt)
+	respondWithImage(r, rw, b, imgURL, procOpt)
 }
 
 func main() {