1 files changed, 74 insertions, 0 deletions
diff --git a/src/image/png/fuzz_test.go b/src/image/png/fuzz_test.go
new file mode 100644
index 0000000..ea4bf4e
--- /dev/null
+++ b/src/image/png/fuzz_test.go
@@ -0,0 +1,74 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package png
+
+import (
+	"bytes"
+	"image"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func FuzzDecode(f *testing.F) {
+	if testing.Short() {
+		f.Skip("Skipping in short mode")
+	}
+
+	testdata, err := os.ReadDir("../testdata")
+	if err != nil {
+		f.Fatalf("failed to read testdata directory: %s", err)
+	}
+	for _, de := range testdata {
+		if de.IsDir() || !strings.HasSuffix(de.Name(), ".png") {
+			continue
+		}
+		b, err := os.ReadFile(filepath.Join("../testdata", de.Name()))
+		if err != nil {
+			f.Fatalf("failed to read testdata: %s", err)
+		}
+		f.Add(b)
+	}
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		cfg, _, err := image.DecodeConfig(bytes.NewReader(b))
+		if err != nil {
+			return
+		}
+		if cfg.Width*cfg.Height > 1e6 {
+			return
+		}
+		img, typ, err := image.Decode(bytes.NewReader(b))
+		if err != nil || typ != "png" {
+			return
+		}
+		levels := []CompressionLevel{
+			DefaultCompression,
+			NoCompression,
+			BestSpeed,
+			BestCompression,
+		}
+		for _, l := range levels {
+			var w bytes.Buffer
+			e := &Encoder{CompressionLevel: l}
+			err = e.Encode(&w, img)
+			if err != nil {
+				t.Errorf("failed to encode valid image: %s", err)
+				continue
+			}
+			img1, err := Decode(&w)
+			if err != nil {
+				t.Errorf("failed to decode roundtripped image: %s", err)
+				continue
+			}
+			got := img1.Bounds()
+			want := img.Bounds()
+			if !got.Eq(want) {
+				t.Errorf("roundtripped image bounds have changed, got: %s, want: %s", got, want)
+			}
+		}
+	})
+}