image-transformer/main.go

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// vi:ts=4:sts=4:sw=4:noet:tw=72
package main
import (
"flag"
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"fmt"
"log"
"net/http"
"strconv"
"strings"
"github.com/davidbyttow/govips/pkg/vips"
)
var (
imgServer = flag.String("s", "https://images.example.com/", "URL prefix")
listenAddr = flag.Int("l", "0.0.0.0:8080", "Listen address")
)
func init() {
flag.Parse()
}
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func main() {
// Start vips with the default configuration
vips.Startup(nil)
defer vips.Shutdown()
http.HandleFunc("/", resizeHandler)
log.Fatal(http.ListenAndServe(listenAddr, nil))
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}
func resizeHandler(w http.ResponseWriter, r *http.Request) {
// Get the query parameters from the request URL
path := r.URL.EscapedPath()
parm := strings.Split(path, "/")
if len(parm) < 3 {
w.Write([]byte(fmt.Sprintf("url, width and height are required")))
w.WriteHeader(http.StatusBadRequest)
return
}
queryUrl := parm[2]
size := strings.Split(parm[1], "x")
if len(size) < 2 {
w.Write([]byte(fmt.Sprintf("url, width and height are required")))
w.WriteHeader(http.StatusBadRequest)
return
}
queryWidth := size[0]
queryHeight := size[1]
// Validate that all three required fields are present
if queryUrl == "" || queryWidth == "" || queryHeight == "" {
w.Write([]byte(fmt.Sprintf("url, width and height are required")))
w.WriteHeader(http.StatusBadRequest)
return
}
// Convert width and height to integers
width, errW := strconv.Atoi(queryWidth)
height, errH := strconv.Atoi(queryHeight)
if errW != nil || errH != nil {
w.Write([]byte(fmt.Sprintf("width and height must be integers")))
w.WriteHeader(http.StatusBadRequest)
return
}
// Start fetching the image from the given url
resp, err := http.Get(imgServer + queryUrl)
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if err != nil {
w.Write([]byte(fmt.Sprintf("failed to get %s: %v", queryUrl, err)))
w.WriteHeader(http.StatusBadRequest)
return
}
// Ensure that a valid response was given
if resp.StatusCode/100 != 2 {
w.Write([]byte(fmt.Sprintf("failed to get %s: status %d", queryUrl, resp.StatusCode)))
w.WriteHeader(http.StatusBadRequest)
return
}
defer resp.Body.Close()
// govips returns the output of the image as a []byte object. We don't need
// it since we are directly piping it to the ResponseWriter
_, _, err = vips.NewTransform().
Load(resp.Body).
ResizeStrategy(vips.ResizeStrategyStretch).
Resize(width, height).
Output(w).
Apply()
if err != nil {
w.Write([]byte(fmt.Sprintf("failed to resize %s: %v", queryUrl, err)))
w.WriteHeader(http.StatusInternalServerError)
return
}
}