From e2ef9fd86ddb97647f7aca80868a5c20824f20f8 Mon Sep 17 00:00:00 2001
From: JP Hastings-Spital <jphastings@gmail.com>
Date: Fri, 23 Sep 2022 23:42:59 +0100
Subject: [PATCH] Adds compatibility with the std image lib

Adding `import _ "github.com/kolesa-team/go-webp"` to a file will allow `image.Decode` to automatically detect and decode WebP files.

Repicates the approach used in [golang.org/x/image/webp](https://cs.opensource.google/go/x/image/+/master:webp/decode.go).
---
 webp.go      | 23 +++++++++++++++++++++++
 webp/webp.go | 21 +++++++++++++++++++--
 2 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 webp.go

diff --git a/webp.go b/webp.go
new file mode 100644
index 0000000..933b645
--- /dev/null
+++ b/webp.go
@@ -0,0 +1,23 @@
+package webp
+
+// Importing this package allows decoding of webp image files using the standard library's image.Decode.
+// It will clash with the golang.org/x/image/webp package
+
+import (
+	"image"
+	"io"
+
+	"github.com/kolesa-team/go-webp/webp"
+)
+
+func init() {
+	image.RegisterFormat("webp", "RIFF????WEBPVP8", quickDecode, quickDecodeConfig)
+}
+
+func quickDecode(r io.Reader) (image.Image, error) {
+	return webp.Decode(r, nil)
+}
+
+func quickDecodeConfig(r io.Reader) (image.Config, error) {
+	return webp.DecodeConfig(r, nil)
+}
diff --git a/webp/webp.go b/webp/webp.go
index 0f9c87d..9c3bf34 100644
--- a/webp/webp.go
+++ b/webp/webp.go
@@ -22,10 +22,12 @@
 package webp
 
 import (
-	"github.com/kolesa-team/go-webp/decoder"
-	"github.com/kolesa-team/go-webp/encoder"
 	"image"
+	"image/color"
 	"io"
+
+	"github.com/kolesa-team/go-webp/decoder"
+	"github.com/kolesa-team/go-webp/encoder"
 )
 
 // Decode picture from reader
@@ -37,6 +39,21 @@ func Decode(r io.Reader, options *decoder.Options) (image.Image, error) {
 	}
 }
 
+// DecodeConfig extracts simple metadata without decoding the image
+func DecodeConfig(r io.Reader, options *decoder.Options) (image.Config, error) {
+	dec, err := decoder.NewDecoder(r, options)
+	if err != nil {
+		return image.Config{}, err
+	}
+
+	feat := dec.GetFeatures()
+	return image.Config{
+		ColorModel: color.NRGBAModel,
+		Width:      feat.Width,
+		Height:     feat.Height,
+	}, nil
+}
+
 // Encode encode picture and write to io.Writer
 func Encode(w io.Writer, src image.Image, options *encoder.Options) error {
 	if enc, err := encoder.NewEncoder(src, options); err != nil {