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// Copyright 2019 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 ccitt
import (
"bytes"
"fmt"
"image"
"image/png"
"io"
"io/ioutil"
"os"
"path/filepath"
"reflect"
"strings"
"testing"
"unsafe"
)
func compareImages(t *testing.T, img0 image.Image, img1 image.Image) {
t.Helper()
b0 := img0.Bounds()
b1 := img1.Bounds()
if b0 != b1 {
t.Fatalf("bounds differ: %v vs %v", b0, b1)
}
for y := b0.Min.Y; y < b0.Max.Y; y++ {
for x := b0.Min.X; x < b0.Max.X; x++ {
c0 := img0.At(x, y)
c1 := img1.At(x, y)
if c0 != c1 {
t.Fatalf("pixel at (%d, %d) differs: %v vs %v", x, y, c0, c1)
}
}
}
}
func decodePNG(fileName string) (image.Image, error) {
f, err := os.Open(fileName)
if err != nil {
return nil, err
}
defer f.Close()
return png.Decode(f)
}
func TestMaxCodeLength(t *testing.T) {
br := bitReader{}
size := unsafe.Sizeof(br.bits)
size *= 8 // Convert from bytes to bits.
// Check that the size of the bitReader.bits field is large enough to hold
// nextBitMaxNBits bits.
if size < nextBitMaxNBits {
t.Fatalf("size: got %d, want >= %d", size, nextBitMaxNBits)
}
// Check that bitReader.nextBit will always leave enough spare bits in the
// bitReader.bits field such that the decode function can unread up to
// maxCodeLength bits.
if want := size - nextBitMaxNBits; maxCodeLength > want {
t.Fatalf("maxCodeLength: got %d, want <= %d", maxCodeLength, want)
}
// The decode function also assumes that, when saving bits to possibly
// unread later, those bits fit inside a uint32.
if maxCodeLength > 32 {
t.Fatalf("maxCodeLength: got %d, want <= %d", maxCodeLength, 32)
}
}
func testDecodeTable(t *testing.T, decodeTable [][2]int16, codes []code, values []uint32) {
// Build a map from values to codes.
m := map[uint32]string{}
for _, code := range codes {
m[code.val] = code.str
}
// Build the encoded form of those values in LSB order.
enc := []byte(nil)
bits := uint8(0)
nBits := uint32(0)
for _, v := range values {
code := m[v]
if code == "" {
panic("unmapped code")
}
for _, c := range code {
bits |= uint8(c&1) << nBits
nBits++
if nBits == 8 {
enc = append(enc, bits)
bits = 0
nBits = 0
}
}
}
if nBits > 0 {
enc = append(enc, bits)
}
// Decode that encoded form.
got := []uint32(nil)
r := &bitReader{
r: bytes.NewReader(enc),
}
finalValue := values[len(values)-1]
for {
v, err := decode(r, decodeTable)
if err != nil {
t.Fatalf("after got=%d: %v", got, err)
}
got = append(got, v)
if v == finalValue {
break
}
}
// Check that the round-tripped values were unchanged.
if !reflect.DeepEqual(got, values) {
t.Fatalf("\ngot: %v\nwant: %v", got, values)
}
}
func TestModeDecodeTable(t *testing.T) {
testDecodeTable(t, modeDecodeTable[:], modeCodes, []uint32{
modePass,
modeV0,
modeV0,
modeVL1,
modeVR3,
modeVL2,
modeExt,
modeVL1,
modeH,
modeVL1,
modeVL1,
modeEOL,
})
}
func TestWhiteDecodeTable(t *testing.T) {
testDecodeTable(t, whiteDecodeTable[:], whiteCodes, []uint32{
0, 1, 256, 7, 128, 3, 2560,
})
}
func TestBlackDecodeTable(t *testing.T) {
testDecodeTable(t, blackDecodeTable[:], blackCodes, []uint32{
63, 64, 63, 64, 64, 63, 22, 1088, 2048, 7, 6, 5, 4, 3, 2, 1, 0,
})
}
func TestDecodeInvalidCode(t *testing.T) {
// The bit stream is:
// 1 010 000000011011
// Packing that LSB-first gives:
// 0b_1101_1000_0000_0101
src := []byte{0x05, 0xD8}
decodeTable := modeDecodeTable[:]
r := &bitReader{
r: bytes.NewReader(src),
}
// "1" decodes to the value 2.
if v, err := decode(r, decodeTable); v != 2 || err != nil {
t.Fatalf("decode #0: got (%v, %v), want (2, nil)", v, err)
}
// "010" decodes to the value 6.
if v, err := decode(r, decodeTable); v != 6 || err != nil {
t.Fatalf("decode #0: got (%v, %v), want (6, nil)", v, err)
}
// "00000001" is an invalid code.
if v, err := decode(r, decodeTable); v != 0 || err != errInvalidCode {
t.Fatalf("decode #0: got (%v, %v), want (0, %v)", v, err, errInvalidCode)
}
// The bitReader should not have advanced after encountering an invalid
// code. The remaining bits should be "000000011011".
remaining := []byte(nil)
for {
bit, err := r.nextBit()
if err == io.EOF {
break
} else if err != nil {
t.Fatalf("nextBit: %v", err)
}
remaining = append(remaining, uint8('0'+bit))
}
if got, want := string(remaining), "000000011011"; got != want {
t.Fatalf("remaining bits: got %q, want %q", got, want)
}
}
func testRead(t *testing.T, fileName string, sf SubFormat, align, invert bool) {
t.Helper()
const width, height = 153, 55
opts := &Options{
Align: align,
Invert: invert,
}
got := ""
{
f, err := os.Open(fileName)
if err != nil {
t.Fatalf("Open: %v", err)
}
defer f.Close()
gotBytes, err := ioutil.ReadAll(NewReader(f, MSB, sf, width, height, opts))
if err != nil {
t.Fatalf("ReadAll: %v", err)
}
got = string(gotBytes)
}
want := ""
{
img, err := decodePNG("testdata/bw-gopher.png")
if err != nil {
t.Fatalf("decodePNG: %v", err)
}
gray, ok := img.(*image.Gray)
if !ok {
t.Fatalf("decodePNG: got %T, want *image.Gray", img)
}
bounds := gray.Bounds()
if w := bounds.Dx(); w != width {
t.Fatalf("width: got %d, want %d", w, width)
}
if h := bounds.Dy(); h != height {
t.Fatalf("height: got %d, want %d", h, height)
}
// Prepare to extend each row's width to a multiple of 8, to simplify
// packing from 1 byte per pixel to 1 bit per pixel.
extended := make([]byte, (width+7)&^7)
wantBytes := []byte(nil)
for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
rowPix := gray.Pix[(y-bounds.Min.Y)*gray.Stride:]
rowPix = rowPix[:width]
copy(extended, rowPix)
// Pack from 1 byte per pixel to 1 bit per pixel, MSB first.
byteValue := uint8(0)
for x, pixel := range extended {
byteValue |= (pixel & 0x80) >> uint(x&7)
if (x & 7) == 7 {
wantBytes = append(wantBytes, byteValue)
byteValue = 0
}
}
}
want = string(wantBytes)
}
// We expect a width of 153 pixels, which is 20 bytes per row (at 1 bit per
// pixel, plus 7 final bits of padding). Check that want is 20 * height
// bytes long, and if got != want, format them to split at every 20 bytes.
if n := len(want); n != 20*height {
t.Fatalf("len(want): got %d, want %d", n, 20*height)
}
format := func(s string) string {
b := []byte(nil)
for row := 0; len(s) >= 20; row++ {
b = append(b, fmt.Sprintf("row%02d: %02X\n", row, s[:20])...)
s = s[20:]
}
if len(s) > 0 {
b = append(b, fmt.Sprintf("%02X\n", s)...)
}
return string(b)
}
if got != want {
t.Fatalf("got:\n%s\nwant:\n%s", format(got), format(want))
}
}
func TestRead(t *testing.T) {
for _, fileName := range []string{
"testdata/bw-gopher.ccitt_group3",
"testdata/bw-gopher-aligned.ccitt_group3",
"testdata/bw-gopher-inverted.ccitt_group3",
"testdata/bw-gopher-inverted-aligned.ccitt_group3",
"testdata/bw-gopher.ccitt_group4",
"testdata/bw-gopher-aligned.ccitt_group4",
"testdata/bw-gopher-inverted.ccitt_group4",
"testdata/bw-gopher-inverted-aligned.ccitt_group4",
} {
subFormat := Group3
if strings.HasSuffix(fileName, "group4") {
subFormat = Group4
}
align := strings.Contains(fileName, "aligned")
invert := strings.Contains(fileName, "inverted")
testRead(t, fileName, subFormat, align, invert)
}
}
func TestDecodeIntoGray(t *testing.T) {
for _, tt := range []struct {
fileName string
sf SubFormat
w, h int
}{
{"testdata/bw-gopher.ccitt_group3", Group3, 153, 55},
{"testdata/bw-gopher.ccitt_group4", Group4, 153, 55},
} {
t.Run(tt.fileName, func(t *testing.T) {
testDecodeIntoGray(t, tt.fileName, MSB, tt.sf, tt.w, tt.h, nil)
})
}
}
func testDecodeIntoGray(t *testing.T, fileName string, order Order, sf SubFormat, width int, height int, opts *Options) {
t.Helper()
f, err := os.Open(filepath.FromSlash(fileName))
if err != nil {
t.Fatalf("Open: %v", err)
}
defer f.Close()
got := image.NewGray(image.Rect(0, 0, width, height))
if err := DecodeIntoGray(got, f, order, sf, opts); err != nil {
t.Fatalf("DecodeIntoGray: %v", err)
}
baseName := fileName[:len(fileName)-len(filepath.Ext(fileName))]
want, err := decodePNG(baseName + ".png")
if err != nil {
t.Fatal(err)
}
compareImages(t, got, want)
}