PNG encoder unit test.

R=rsc,r
APPROVED=r
DELTA=84  (77 added, 6 deleted, 1 changed)
OCL=35456
CL=35458

2 files changed, 78 insertions, 7 deletions

diff --git a/src/pkg/image/png/reader_test.go b/src/pkg/image/png/reader_test.go
index 4aa3c0a2a..4bc6d891e 100644
--- a/src/pkg/image/png/reader_test.go
+++ b/src/pkg/image/png/reader_test.go
@@ -33,6 +33,14 @@ var filenames = []string {
 	//"basn6a16",	// bit depth is not 8
 }
 
+func readPng(filename string) (image.Image, os.Error) {
+	f, err := os.Open(filename, os.O_RDONLY, 0444);
+	if err != nil {
+		return nil, err;
+	}
+	defer f.Close();
+	return Decode(f);
+}
 
 // An approximation of the sng command-line tool.
 func sng(w io.WriteCloser, filename string, png image.Image) {
@@ -103,13 +111,7 @@ func sng(w io.WriteCloser, filename string, png image.Image) {
 func TestReader(t *testing.T) {
 	for _, fn := range filenames {
 		// Read the .png file.
-		pf, err := os.Open("testdata/pngsuite/" + fn + ".png", os.O_RDONLY, 0444);
-		if err != nil {
-			t.Error(fn, err);
-			continue
-		}
-		defer pf.Close();
-		image, err := Decode(pf);
+		image, err := readPng("testdata/pngsuite/" + fn + ".png");
 		if err != nil {
 			t.Error(fn, err);
 			continue
diff --git a/src/pkg/image/png/writer_test.go b/src/pkg/image/png/writer_test.go
new file mode 100644
index 000000000..b832f1c26
--- /dev/null
+++ b/src/pkg/image/png/writer_test.go
@@ -0,0 +1,69 @@
+// Copyright 2009 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 (
+	"fmt";
+	"image";
+	"io";
+	"os";
+	"testing";
+)
+
+func diff(m0, m1 image.Image) os.Error {
+	if m0.Width() != m1.Width() || m0.Height() != m1.Height() {
+		return os.NewError(fmt.Sprintf("dimensions differ: %dx%d vs %dx%d", m0.Width(), m0.Height(), m1.Width(), m1.Height()));
+	}
+	for y := 0; y < m0.Height(); y++ {
+		for x := 0; x < m0.Width(); x++ {
+			r0, g0, b0, a0 := m0.At(x, y).RGBA();
+			r1, g1, b1, a1 := m1.At(x, y).RGBA();
+			if r0 != r1 || g0 != g1 || b0 != b1 || a0 != a1 {
+				return os.NewError(fmt.Sprintf("colors differ at (%d, %d): %v vs %v", x, y, m0.At(x, y), m1.At(x, y)));
+			}
+		}
+	}
+	return nil;
+}
+
+func TestWriter(t *testing.T) {
+	// The filenames variable is declared in reader_test.go.
+	for _, fn := range filenames {
+		qfn := "testdata/pngsuite/" + fn + ".png";
+		// Read the image.
+		m0, err := readPng(qfn);
+		if err != nil {
+			t.Error(fn, err);
+			continue;
+		}
+		// Read the image again, and push it through a pipe that encodes at the write end, and decodes at the read end.
+		pr, pw := io.Pipe();
+		defer pr.Close();
+		go func() {
+			defer pw.Close();
+			m1, err := readPng(qfn);
+			if err != nil {
+				t.Error(fn, err);
+				return;
+			}
+			err = Encode(pw, m1);
+			if err != nil {
+				t.Error(fn, err);
+				return;
+			}
+		}();
+		m2, err := Decode(pr);
+		if err != nil {
+			t.Error(fn, err);
+			continue;
+		}
+		// Compare the two.
+		err = diff(m0, m2);
+		if err != nil {
+			t.Error(fn, err);
+			continue;
+		}
+	}
+}