src/pkg/image/png/writer_test.go

// 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;
		}
	}
}