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|
package api
import (
"bytes"
"errors"
"fmt"
"image"
"image/jpeg"
"image/png"
"io"
"net/http"
"path/filepath"
"strings"
"github.com/mediocregopher/blog.mediocregopher.com/srv/api/apiutil"
"github.com/mediocregopher/blog.mediocregopher.com/srv/post"
"golang.org/x/image/draw"
)
func resizeImage(out io.Writer, in io.Reader, maxWidth float64) error {
img, format, err := image.Decode(in)
if err != nil {
return fmt.Errorf("decoding image: %w", err)
}
imgRect := img.Bounds()
imgW, imgH := float64(imgRect.Dx()), float64(imgRect.Dy())
if imgW > maxWidth {
newH := imgH * maxWidth / imgW
newImg := image.NewRGBA(image.Rect(0, 0, int(maxWidth), int(newH)))
// Resize
draw.BiLinear.Scale(
newImg, newImg.Bounds(), img, img.Bounds(), draw.Over, nil,
)
img = newImg
}
switch format {
case "jpeg":
return jpeg.Encode(out, img, nil)
case "png":
return png.Encode(out, img)
default:
return fmt.Errorf("unknown image format %q", format)
}
}
func (a *api) servePostAssetHandler() http.Handler {
return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
id := filepath.Base(r.URL.Path)
maxWidth, err := apiutil.StrToInt(r.FormValue("w"), 0)
if err != nil {
apiutil.BadRequest(rw, r, fmt.Errorf("invalid w parameter: %w", err))
return
}
buf := new(bytes.Buffer)
err = a.params.PostAssetStore.Get(id, buf)
if errors.Is(err, post.ErrAssetNotFound) {
http.Error(rw, "Asset not found", 404)
return
} else if err != nil {
apiutil.InternalServerError(
rw, r, fmt.Errorf("fetching asset with id %q: %w", id, err),
)
return
}
if maxWidth == 0 {
if _, err := io.Copy(rw, buf); err != nil {
apiutil.InternalServerError(
rw, r,
fmt.Errorf(
"copying asset with id %q to response writer: %w",
id, err,
),
)
}
return
}
switch ext := strings.ToLower(strings.TrimPrefix(filepath.Ext(id), ".")); ext {
case "jpg", "jpeg", "png":
if err := resizeImage(rw, buf, float64(maxWidth)); err != nil {
apiutil.InternalServerError(
rw, r,
fmt.Errorf(
"resizing image with id %q to size %d: %w",
id, maxWidth, err,
),
)
}
default:
apiutil.BadRequest(rw, r, fmt.Errorf("cannot resize file with extension %q", ext))
return
}
})
}
|
