Make requested changes according to the PR comments

Add default parameters to the NewCCITTFaxEncoder. Default values
are taken from the PDF specification.
ccittfaxdecode was moved to pdf/internal and renamed to ccittfax.
ccittfax package errors were unexported.

pdf/core/encoding.go

@@ -34,7 +34,7 @@ import (
 	lzw1 "golang.org/x/image/tiff/lzw"
 
 	"github.com/unidoc/unidoc/common"
-	"github.com/unidoc/unidoc/pdf/core/ccittfaxdecode"
+	"github.com/unidoc/unidoc/pdf/internal/ccittfax"
 )
 
 const (
@@ -1633,7 +1633,10 @@ type CCITTFaxEncoder struct {
 
 // NewCCITTFaxEncoder makes a new CCITTFax encoder.
 func NewCCITTFaxEncoder() *CCITTFaxEncoder {
-	return &CCITTFaxEncoder{}
+	return &CCITTFaxEncoder{
+		Columns:    1728,
+		EndOfBlock: true,
+	}
 }
 
 // GetFilterName gets the filter name.
@@ -1842,7 +1845,7 @@ func (enc *CCITTFaxEncoder) UpdateParams(params *PdfObjectDictionary) {
 
 // DecodeBytes decodes the CCITTFax encoded image data.
 func (enc *CCITTFaxEncoder) DecodeBytes(encoded []byte) ([]byte, error) {
-	encoder := &ccittfaxdecode.Encoder{
+	encoder := &ccittfax.Encoder{
 		K:                      enc.K,
 		Columns:                enc.Columns,
 		EndOfLine:              enc.EndOfLine,
@@ -1913,7 +1916,7 @@ func (enc *CCITTFaxEncoder) EncodeBytes(data []byte) ([]byte, error) {
 		pixels = append(pixels, pixelsRow)
 	}
 
-	encoder := &ccittfaxdecode.Encoder{
+	encoder := &ccittfax.Encoder{
 		K:                      enc.K,
 		Columns:                enc.Columns,
 		EndOfLine:              enc.EndOfLine,

pdf/creator/creator_test.go

@@ -59,6 +59,7 @@ const testImageFile2 = "./testdata/signature.png"
 const testRobotoRegularTTFFile = "./testdata/roboto/Roboto-Regular.ttf"
 const testRobotoBoldTTFFile = "./testdata/roboto/Roboto-Bold.ttf"
 const testWts11TTFFile = "./testdata/wts11.ttf"
+const testImageFileCCITT = "./testdata/p3_0.png"
 
 // TODO(peterwilliams97): /tmp/2_p_multi.pdf which is created in this test gives an error message
 //      when opened in Adobe Reader: The font FreeSans contains bad Widths.
@@ -166,6 +167,58 @@ func TestImageWithEncoder(t *testing.T) {
 	testWriteAndRender(t, creator, "1_dct.pdf")
 }
 
+func TestImageWithCCITTFaxEncoder(t *testing.T) {
+	creator := New()
+
+	file, err := os.Open(testImageFileCCITT)
+	if err != nil {
+		t.Errorf("Error opening test image file: %v\n", err)
+		return
+	}
+
+	imgF, _, err := goimage.Decode(file)
+	if err != nil {
+		file.Close()
+		t.Errorf("Error decoding test image file: %v\n", err)
+		return
+	}
+
+	file.Close()
+
+	modelImg, err := model.ImageHandling.NewImageFromGoImage(imgF)
+	if err != nil {
+		t.Errorf("Error creating image from go image: %v\n", err)
+		return
+	}
+
+	modelImg.BitsPerComponent = 1
+	modelImg.ColorComponents = 1
+
+	img, err := creator.NewImage(modelImg)
+	if err != nil {
+		t.Errorf("Error creating image: %v\n", err)
+		return
+	}
+
+	encoder := core.NewCCITTFaxEncoder()
+	encoder.Columns = int(img.Width())
+	img.SetEncoder(encoder)
+
+	img.SetPos(0, 0)
+	img.ScaleToWidth(612.0)
+	height := 612.0 * img.Height() / img.Width()
+	creator.SetPageSize(PageSize{612, height})
+	creator.NewPage()
+
+	err = creator.Draw(img)
+	if err != nil {
+		t.Errorf("Fail: %v\n", err)
+		return
+	}
+
+	testWriteAndRender(t, creator, "1_ccitt.pdf")
+}
+
 func TestShapes1(t *testing.T) {
 	creator := New()
 

pdf/internal/ccittfax/codes.go

@@ -3,9 +3,10 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-package ccittfaxdecode
+package ccittfax
 
 // map pixel run lengths to the encoded bit sequences
+// all the bit sequences for all groups could be found here https://www.itu.int/rec/T-REC-T.6-198811-I/en
 var (
 	bTerms        map[int]code
 	wTerms        map[int]code

pdf/internal/ccittfax/decode.go

@@ -3,29 +3,31 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-package ccittfaxdecode
+package ccittfax
 
 import (
 	"errors"
 )
 
 var (
-	// ErrEOFBCorrupt is returned when the corrupt EOFB (end-of-block) code is found.
-	ErrEOFBCorrupt = errors.New("EOFB code is corrupted")
-	// ErrRTCCorrupt is returned when the corrupt RTC (return-the-carriage) code is found.
-	ErrRTCCorrupt = errors.New("RTC code is corrupted")
-	// ErrWrongCodeInHorizontalMode is returned when entered the horizontal mode and unknown bit
+	// errEOFBCorrupt is returned when the corrupt EOFB (end-of-block) code is found.
+	errEOFBCorrupt = errors.New("EOFB code is corrupted")
+	// errRTCCorrupt is returned when the corrupt RTC (return-the-carriage) code is found.
+	errRTCCorrupt = errors.New("RTC code is corrupted")
+	// errWrongCodeInHorizontalMode is returned when entered the horizontal mode and unknown bit
 	// sequence met.
-	ErrWrongCodeInHorizontalMode = errors.New("wrong code in horizontal mode")
-	// ErrNoEOLFound is returned when the EndOfLine parameter is true in filter but no EOL (end-of-line) met.
-	ErrNoEOLFound = errors.New("no EOL found while the EndOfLine parameter is true")
-	// ErrInvalidEOL is returned when the EOL code is corrupt.
-	ErrInvalidEOL = errors.New("invalid EOL")
-	// ErrInvalid2DCode is returned when the invalid 2 dimensional code is met. 2 dimensional code
+	errWrongCodeInHorizontalMode = errors.New("wrong code in horizontal mode")
+	// errNoEOLFound is returned when the EndOfLine parameter is true in filter but no EOL (end-of-line) met.
+	errNoEOLFound = errors.New("no EOL found while the EndOfLine parameter is true")
+	// errInvalidEOL is returned when the EOL code is corrupt.
+	errInvalidEOL = errors.New("invalid EOL")
+	// errInvalid2DCode is returned when the invalid 2 dimensional code is met. 2 dimensional code
 	// according to the CCITT reccommendations is one of the following: H, P, V0, V1L, V2L, V3L, V1R, V2R, V3R.
-	ErrInvalid2DCode = errors.New("invalid 2D code")
+	errInvalid2DCode = errors.New("invalid 2D code")
+)
 
-	// trees represent the finite state machine for parsing bit sequences and fetching pixel run lengths
+// trees represent the finite state machine for parsing bit sequences and fetching pixel run lengths
+var (
 	whiteTree = &decodingTreeNode{
 		Val: 255,
 	}
@@ -112,7 +114,7 @@ func (e *Encoder) decodeG31D(encoded []byte) ([][]byte, error) {
 		gotEOL, bitPos = tryFetchEOL(encoded, bitPos)
 		if !gotEOL {
 			if e.EndOfLine {
-				return nil, ErrNoEOLFound
+				return nil, errNoEOLFound
 			}
 		} else {
 			// 5 EOLs left to fill RTC
@@ -124,7 +126,7 @@ func (e *Encoder) decodeG31D(encoded []byte) ([][]byte, error) {
 						break
 					}
 
-					return nil, ErrInvalidEOL
+					return nil, errInvalidEOL
 				}
 			}
 
@@ -176,7 +178,7 @@ byteLoop:
 
 		if !gotEOL {
 			if e.EndOfLine {
-				return nil, ErrNoEOLFound
+				return nil, errNoEOLFound
 			}
 		}
 
@@ -212,7 +214,7 @@ byteLoop:
 					break byteLoop
 				} else {
 					if e.EndOfLine {
-						return nil, ErrNoEOLFound
+						return nil, errNoEOLFound
 					}
 				}
 			}
@@ -238,31 +240,24 @@ byteLoop:
 					}
 				case v0:
 					pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 0)
-
 					isWhite = !isWhite
 				case v1r:
 					pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 1)
-
 					isWhite = !isWhite
 				case v2r:
 					pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 2)
-
 					isWhite = !isWhite
 				case v3r:
 					pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 3)
-
 					isWhite = !isWhite
 				case v1l:
 					pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, -1)
-
 					isWhite = !isWhite
 				case v2l:
 					pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, -2)
-
 					isWhite = !isWhite
 				case v3l:
 					pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, -3)
-
 					isWhite = !isWhite
 				}
 
@@ -327,7 +322,7 @@ func (e *Encoder) decodeG4(encoded []byte) ([][]byte, error) {
 		for a0 < e.Columns {
 			twoDimCode, bitPos, ok = fetchNext2DCode(encoded, bitPos)
 			if !ok {
-				return nil, ErrInvalid2DCode
+				return nil, errInvalid2DCode
 			}
 
 			switch twoDimCode {
@@ -342,31 +337,24 @@ func (e *Encoder) decodeG4(encoded []byte) ([][]byte, error) {
 				}
 			case v0:
 				pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 0)
-
 				isWhite = !isWhite
 			case v1r:
 				pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 1)
-
 				isWhite = !isWhite
 			case v2r:
 				pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 2)
-
 				isWhite = !isWhite
 			case v3r:
 				pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, 3)
-
 				isWhite = !isWhite
 			case v1l:
 				pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, -1)
-
 				isWhite = !isWhite
 			case v2l:
 				pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, -2)
-
 				isWhite = !isWhite
 			case v3l:
 				pixelsRow, a0 = decodeVerticalMode(pixels, pixelsRow, isWhite, a0, -3)
-
 				isWhite = !isWhite
 			}
 
@@ -456,7 +444,7 @@ func decodeHorizontalMode(encoded, pixelsRow []byte, bitPos int, isWhite bool, a
 
 // decodeNextRunLen decodes tries to decode the next part of data using the Group3 1-dimensional code.
 // Returns moved bit position and the pixels row filled with the decoded pixels. The returned bit position
-// is not moved if the error occurs. Returns `ErrWrongCodeInHorizontalMode` if none of the 1-dimensional codes found.
+// is not moved if the error occurs. Returns `errWrongCodeInHorizontalMode` if none of the 1-dimensional codes found.
 func decodeNextRunLen(encoded, pixelsRow []byte, bitPos int, isWhite bool) ([]byte, int, error) {
 	startingBitPos := bitPos
 
@@ -472,7 +460,7 @@ func decodeNextRunLen(encoded, pixelsRow []byte, bitPos int, isWhite bool) ([]by
 	}
 
 	if runLen == -1 {
-		return pixelsRow, startingBitPos, ErrWrongCodeInHorizontalMode
+		return pixelsRow, startingBitPos, errWrongCodeInHorizontalMode
 	}
 
 	return pixelsRow, bitPos, nil
@@ -480,7 +468,7 @@ func decodeNextRunLen(encoded, pixelsRow []byte, bitPos int, isWhite bool) ([]by
 
 // tryFetchRTC2D tries to fetch the RTC code (0000000000011 X 6) for Group3 mixed (1D/2D) dimensional encoding from
 // the encoded data. Returns the moved bit position if the code was found. The other way returns the
-// the original bit position. The `ErrRTCCorrupt` is returned if the RTC code is corrupt. The RTC code is considered
+// the original bit position. The `errRTCCorrupt` is returned if the RTC code is corrupt. The RTC code is considered
 // corrupt if there are more than one EOL1 code (0000000000011) is met.
 func tryFetchRTC2D(encoded []byte, bitPos int) (bool, int, error) {
 	startingBitPos := bitPos
@@ -492,7 +480,7 @@ func tryFetchRTC2D(encoded []byte, bitPos int) (bool, int, error) {
 
 		if !gotEOL {
 			if i > 1 {
-				return false, startingBitPos, ErrRTCCorrupt
+				return false, startingBitPos, errRTCCorrupt
 			} else {
 				bitPos = startingBitPos
 
@@ -506,7 +494,7 @@ func tryFetchRTC2D(encoded []byte, bitPos int) (bool, int, error) {
 
 // tryFetchEOFB tries to fetch the EOFB code (000000000001 X 2) for Group4 encoding from
 // the encoded data. Returns the moved bit position if the code was found. The other way returns the
-// the original bit position. The `ErrEOFBCorrupt` is returned if the EOFB code is corrupt. The EOFB code is considered
+// the original bit position. The `errEOFBCorrupt` is returned if the EOFB code is corrupt. The EOFB code is considered
 // corrupt if there is a single EOL code (000000000001).
 func tryFetchEOFB(encoded []byte, bitPos int) (bool, int, error) {
 	startingBitPos := bitPos
@@ -520,7 +508,7 @@ func tryFetchEOFB(encoded []byte, bitPos int) (bool, int, error) {
 		if gotEOL {
 			return true, bitPos, nil
 		} else {
-			return false, startingBitPos, ErrEOFBCorrupt
+			return false, startingBitPos, errEOFBCorrupt
 		}
 	}
 

pdf/internal/ccittfax/decode_test.go

@@ -3,7 +3,7 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-package ccittfaxdecode
+package ccittfax
 
 import (
 	"image"
@@ -32,6 +32,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 		Want      testResult
 	}
 
+	// Calculated test data based on the reference documentation.
 	tests := []testData{
 		{
 			Encoded:   []byte{1, 28, 2},
@@ -179,7 +180,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    0,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -190,7 +191,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    2,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -201,7 +202,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    0,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -212,7 +213,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    2,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -223,7 +224,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    0,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -234,7 +235,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    2,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -245,7 +246,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    0,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -256,7 +257,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    2,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -267,7 +268,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    0,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -278,7 +279,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    2,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -289,7 +290,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    0,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -300,7 +301,7 @@ func TestDecodeNextRunLen(t *testing.T) {
 			Want: testResult{
 				PixelsRow: nil,
 				BitPos:    2,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 	}
@@ -415,7 +416,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    0,
 				A0:        0,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -428,7 +429,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    2,
 				A0:        120,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -441,7 +442,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    0,
 				A0:        10,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -454,7 +455,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    2,
 				A0:        13,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -467,7 +468,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    0,
 				A0:        23,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -480,7 +481,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    2,
 				A0:        34,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -493,7 +494,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    0,
 				A0:        134,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -506,7 +507,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    2,
 				A0:        35,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -519,7 +520,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    0,
 				A0:        876,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -532,7 +533,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    2,
 				A0:        738,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -545,7 +546,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    0,
 				A0:        283,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -558,7 +559,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 				PixelsRow: nil,
 				BitPos:    2,
 				A0:        29,
-				Err:       ErrWrongCodeInHorizontalMode,
+				Err:       errWrongCodeInHorizontalMode,
 			},
 		},
 		{
@@ -573,7 +574,7 @@ func TestDecodeHorizontalMode(t *testing.T) {
 					white, white, white},
 				BitPos: 16,
 				A0:     0,
-				Err:    ErrWrongCodeInHorizontalMode,
+				Err:    errWrongCodeInHorizontalMode,
 			},
 		},
 	}
@@ -2005,7 +2006,7 @@ func TestTryFetchEOFB(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 0,
-				Err:    ErrEOFBCorrupt,
+				Err:    errEOFBCorrupt,
 			},
 		},
 		{
@@ -2099,7 +2100,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 0,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{
@@ -2108,7 +2109,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 2,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{
@@ -2117,7 +2118,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 0,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{
@@ -2126,7 +2127,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 2,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{
@@ -2135,7 +2136,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 0,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{
@@ -2144,7 +2145,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 2,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{
@@ -2153,7 +2154,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 0,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{
@@ -2162,7 +2163,7 @@ func TestTryFetchRTC2D(t *testing.T) {
 			Want: testResult{
 				OK:     false,
 				BitPos: 2,
-				Err:    ErrRTCCorrupt,
+				Err:    errRTCCorrupt,
 			},
 		},
 		{

pdf/internal/ccittfax/decoding_tree.go

@@ -3,7 +3,7 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-package ccittfaxdecode
+package ccittfax
 
 // decodingTreeNode is a node of a tree which represents the finite state machine for
 // searching the decoded pixel run lengths having the bit sequence. `Val` is a single bit

pdf/internal/ccittfax/decoding_tree_test.go

@@ -3,7 +3,7 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-package ccittfaxdecode
+package ccittfax
 
 import (
 	"testing"

pdf/internal/ccittfax/doc.go

@@ -3,7 +3,7 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-// Package ccittfaxdecode defines and implements the Group3 and Group4
+// Package ccittfax defines and implements the Group3 and Group4
 // facsimile (fax) encoding and decoding according to the CCITT recommendations
 // T.4 and T.6.
-package ccittfaxdecode
+package ccittfax

pdf/internal/ccittfax/encoder.go

@@ -3,7 +3,7 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-package ccittfaxdecode
+package ccittfax
 
 import (
 	"math"
@@ -68,7 +68,6 @@ func (e *Encoder) encodeG31D(pixels [][]byte) []byte {
 		}
 
 		encodedRow, bitPos := encodeRow1D(pixels[i], prevBitPos, eol)
-
 		encoded = e.appendEncodedRow(encoded, encodedRow, prevBitPos)
 
 		if e.EncodedByteAlign {
@@ -82,7 +81,6 @@ func (e *Encoder) encodeG31D(pixels [][]byte) []byte {
 	if e.EndOfBlock {
 		// put RTC
 		encodedRTC, _ := encodeRTC(prevBitPos)
-
 		encoded = e.appendEncodedRow(encoded, encodedRTC, prevBitPos)
 	}
 
@@ -210,7 +208,6 @@ func (e *Encoder) encodeG4(pixelsToEncode [][]byte) []byte {
 		}
 
 		encoded = e.appendEncodedRow(encoded, encodedRow, prevBitPos)
-
 		if e.EncodedByteAlign {
 			// align to byte border
 			bitPos = 0
@@ -222,7 +219,6 @@ func (e *Encoder) encodeG4(pixelsToEncode [][]byte) []byte {
 	if e.EndOfBlock {
 		// put EOFB
 		encodedEOFB, _ := encodeEOFB(prevBitPos)
-
 		encoded = e.appendEncodedRow(encoded, encodedEOFB, prevBitPos)
 	}
 

pdf/internal/ccittfax/encoder_test.go

@@ -3,11 +3,10 @@
  * file 'LICENSE.md', which is part of this source code package.
  */
 
-package ccittfaxdecode
+package ccittfax
 
 import (
-	"image"
-	"image/png"
+	_ "image/png"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -20,8 +19,6 @@ func TestEncode(t *testing.T) {
 		WantFilePath string
 	}
 
-	image.RegisterFormat("png", "png", png.Decode, png.DecodeConfig)
-
 	pixels, err := getPixels(testDataPath + "p3_0.png")
 	if err != nil {
 		t.Fatalf("Error getting pixels from image: %v\n", err)