JBIG2 Encoder support for inserting binary images into PDF (#288)

* Added JBIG2 PDF support
* Added JBIG2 Encoder binary image requirements
* PR #288 revision r1 fixes
* PR #288 revision r2 fixes

contentstream/inline-image.go

@@ -37,6 +37,7 @@ func NewInlineImageFromImage(img model.Image, encoder core.StreamEncoder) (*Cont
 	if encoder == nil {
 		encoder = core.NewRawEncoder()
 	}
+	encoder.UpdateParams(img.GetParamsDict())
 
 	inlineImage := ContentStreamInlineImage{}
 	if img.ColorComponents == 1 {

core/encoding_jbig2.go

@@ -6,11 +6,11 @@
 package core
 
 import (
-	"bytes"
 	"image"
 	"image/color"
 
 	"github.com/unidoc/unipdf/v3/common"
+	"github.com/unidoc/unipdf/v3/internal/imageutil"
 
 	"github.com/unidoc/unipdf/v3/internal/jbig2"
 	"github.com/unidoc/unipdf/v3/internal/jbig2/bitmap"
@@ -55,6 +55,17 @@ const JB2ImageAutoThreshold = -1.0
 // The similarity is defined by the 'Threshold' variable (default: 0.95). The less the value is, the more components
 // matches to single class, thus the compression is better, but the result might become lossy.
 type JBIG2Encoder struct {
+	// These values are required to be set for the 'EncodeBytes' method.
+	// ColorComponents defines the number of color components for provided image.
+	ColorComponents int
+	// BitsPerComponent is the number of bits that stores per color component
+	BitsPerComponent int
+	// Width is the width of the image to encode
+	Width int
+	// Height is the height of the image to encode.
+	Height int
+
+	// Encode Page and Decode parameters
 	d *document.Document
 	// Globals are the JBIG2 global segments.
 	Globals jbig2.Globals
@@ -69,7 +80,9 @@ type JBIG2Encoder struct {
 
 // NewJBIG2Encoder creates a new JBIG2Encoder.
 func NewJBIG2Encoder() *JBIG2Encoder {
-	return &JBIG2Encoder{}
+	return &JBIG2Encoder{
+		d: document.InitEncodeDocument(false),
+	}
 }
 
 // AddPageImage adds the page with the image 'img' to the encoder context in order to encode it jbig2 document.
@@ -165,18 +178,31 @@ func (enc *JBIG2Encoder) DecodeStream(streamObj *PdfObjectStream) ([]byte, error
 // to encode given image.
 func (enc *JBIG2Encoder) EncodeBytes(data []byte) ([]byte, error) {
 	const processName = "JBIG2Encoder.EncodeBytes"
-	if len(data) == 0 {
-		return nil, errors.Errorf(processName, "input 'data' not defined")
+	if enc.ColorComponents != 1 || enc.BitsPerComponent != 1 {
+		return nil, errors.Errorf(processName, "provided invalid input image. JBIG2 Encoder requires binary images data")
 	}
-	i, _, err := image.Decode(bytes.NewReader(data))
+	b, err := bitmap.NewWithUnpaddedData(enc.Width, enc.Height, data)
 	if err != nil {
-		return nil, errors.Wrap(err, processName, "decode input image")
+		return nil, err
 	}
-	encoded, err := enc.encodeImage(i)
-	if err != nil {
+	settings := enc.DefaultPageSettings
+	if err = settings.Validate(); err != nil {
 		return nil, errors.Wrap(err, processName, "")
 	}
-	return encoded, nil
+
+	switch settings.Compression {
+	case JB2Generic:
+		if err = enc.d.AddGenericPage(b, settings.DuplicatedLinesRemoval); err != nil {
+			return nil, errors.Wrap(err, processName, "")
+		}
+	case JB2SymbolCorrelation:
+		return nil, errors.Error(processName, "symbol correlation encoding not implemented yet")
+	case JB2SymbolRankHaus:
+		return nil, errors.Error(processName, "symbol rank haus encoding not implemented yet")
+	default:
+		return nil, errors.Error(processName, "provided invalid compression")
+	}
+	return enc.Encode()
 }
 
 // EncodeImage encodes 'img' golang image.Image into jbig2 encoded bytes document using default encoder settings.
@@ -184,6 +210,15 @@ func (enc *JBIG2Encoder) EncodeImage(img image.Image) ([]byte, error) {
 	return enc.encodeImage(img)
 }
 
+// EncodeJBIG2Image encodes 'img' into jbig2 encoded bytes stream, using default encoder settings.
+func (enc *JBIG2Encoder) EncodeJBIG2Image(img *JBIG2Image) ([]byte, error) {
+	const processName = "core.EncodeJBIG2Image"
+	if err := enc.AddPageImage(img, &enc.DefaultPageSettings); err != nil {
+		return nil, errors.Wrap(err, processName, "")
+	}
+	return enc.Encode()
+}
+
 // Encode encodes previously prepare jbig2 document and stores it as the byte slice.
 func (enc *JBIG2Encoder) Encode() (data []byte, err error) {
 	const processName = "JBIG2Document.Encode"
@@ -217,8 +252,24 @@ func (enc *JBIG2Encoder) MakeStreamDict() *PdfObjectDictionary {
 }
 
 // UpdateParams updates the parameter values of the encoder.
-// The body of this method is empty but required to implement StreamEncoder interface.
+// Implements StreamEncoder interface.
 func (enc *JBIG2Encoder) UpdateParams(params *PdfObjectDictionary) {
+	bpc, err := GetNumberAsInt64(params.Get("BitsPerComponent"))
+	if err == nil {
+		enc.BitsPerComponent = int(bpc)
+	}
+	width, err := GetNumberAsInt64(params.Get("Width"))
+	if err == nil {
+		enc.Width = int(width)
+	}
+	height, err := GetNumberAsInt64(params.Get("Height"))
+	if err == nil {
+		enc.Height = int(height)
+	}
+	colorComponents, err := GetNumberAsInt64(params.Get("ColorComponents"))
+	if err == nil {
+		enc.ColorComponents = int(colorComponents)
+	}
 }
 
 func (enc *JBIG2Encoder) encodeImage(i image.Image) ([]byte, error) {
@@ -262,24 +313,29 @@ func newJBIG2DecoderFromStream(streamObj *PdfObjectStream, decodeParams *PdfObje
 			}
 		}
 	}
-
-	if decodeParams != nil {
-		if globals := decodeParams.Get("JBIG2Globals"); globals != nil {
-			var err error
-
-			globalsStream, ok := globals.(*PdfObjectStream)
-			if !ok {
-				err = errors.Error(processName, "jbig2.Globals stream should be an Object Stream")
-				common.Log.Debug("ERROR: %s", err.Error())
-				return nil, err
-			}
-			encoder.Globals, err = jbig2.DecodeGlobals(globalsStream.Stream)
-			if err != nil {
-				err = errors.Wrap(err, processName, "corrupted jbig2 encoded data")
-				common.Log.Debug("ERROR: %s", err)
-				return nil, err
-			}
-		}
+	// if no decode params provided - end fast.
+	if decodeParams == nil {
+		return encoder, nil
+	}
+	// set image parameters.
+	encoder.UpdateParams(decodeParams)
+	globals := decodeParams.Get("JBIG2Globals")
+	if globals == nil {
+		return encoder, nil
+	}
+	// decode and set JBIG2 Globals.
+	var err error
+	globalsStream, ok := globals.(*PdfObjectStream)
+	if !ok {
+		err = errors.Error(processName, "jbig2.Globals stream should be an Object Stream")
+		common.Log.Debug("ERROR: %v", err)
+		return nil, err
+	}
+	encoder.Globals, err = jbig2.DecodeGlobals(globalsStream.Stream)
+	if err != nil {
+		err = errors.Wrap(err, processName, "corrupted jbig2 encoded data")
+		common.Log.Debug("ERROR: %v", err)
+		return nil, err
 	}
 	return encoder, nil
 }
@@ -348,9 +404,9 @@ func GoImageToJBIG2(i image.Image, bwThreshold float64) (*JBIG2Image, error) {
 	var th uint8
 	if bwThreshold == JB2ImageAutoThreshold {
 		// autoThreshold using triangle method
-		gray := bitmap.ImgToGray(i)
-		histogram := bitmap.GrayImageHistogram(gray)
-		th = bitmap.AutoThresholdTriangle(histogram)
+		gray := imageutil.ImgToGray(i)
+		histogram := imageutil.GrayImageHistogram(gray)
+		th = imageutil.AutoThresholdTriangle(histogram)
 		i = gray
 	} else if bwThreshold > 1.0 || bwThreshold < 0.0 {
 		// check if bwThreshold is unknown - set to 0.0 is not in the allowed range.
@@ -358,7 +414,7 @@ func GoImageToJBIG2(i image.Image, bwThreshold float64) (*JBIG2Image, error) {
 	} else {
 		th = uint8(255 * bwThreshold)
 	}
-	gray := bitmap.ImgToBinary(i, th)
+	gray := imageutil.ImgToBinary(i, th)
 	return bwToJBIG2Image(gray), nil
 }
 

creator/image.go

@@ -158,6 +158,13 @@ func (img *Image) GetMargins() (float64, float64, float64, float64) {
 	return img.margins.left, img.margins.right, img.margins.top, img.margins.bottom
 }
 
+// ConvertToBinary converts current image data into binary (Bi-level image) format.
+// If provided image is RGB or GrayScale the function converts it into binary image
+// using histogram auto threshold method.
+func (img *Image) ConvertToBinary() error {
+	return img.img.ConvertToBinary()
+}
+
 // makeXObject makes the encoded XObject Image that will be used in the PDF.
 func (img *Image) makeXObject() error {
 	encoder := img.encoder
@@ -181,7 +188,10 @@ func (img *Image) makeXObject() error {
 func (img *Image) GeneratePageBlocks(ctx DrawContext) ([]*Block, DrawContext, error) {
 	if img.xobj == nil {
 		// Build the XObject Image if not already prepared.
-		img.makeXObject()
+		if err := img.makeXObject(); err != nil {
+			return nil, ctx, err
+		}
+
 	}
 
 	var blocks []*Block

go.sum

@@ -8,6 +8,7 @@ github.com/boombuler/barcode v1.0.0 h1:s1TvRnXwL2xJRaccrdcBQMZxq6X7DvsMogtmJeHDd
 github.com/boombuler/barcode v1.0.0/go.mod h1:paBWMcWSl3LHKBqUq+rly7CNSldXjb2rDl3JlRe0mD8=
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
 github.com/gunnsth/pkcs7 v0.0.0-20181213175627-3cffc6fbfe83 h1:saj5dTV7eQ1wFg/gVZr1SfbkOmg8CYO9R8frHgQiyR4=
 github.com/gunnsth/pkcs7 v0.0.0-20181213175627-3cffc6fbfe83/go.mod h1:xaGEIRenAiJcGgd9p62zbiP4993KaV3PdjczwGnP50I=

internal/imageutil/rgbtobw.go

@@ -1,4 +1,4 @@
-package bitmap
+package imageutil
 
 import (
 	"image"
@@ -131,6 +131,11 @@ func ImgToGray(i image.Image) *image.Gray {
 	return g
 }
 
+// IsGrayImgBlackAndWhite checks if provided gray image is BlackAndWhite - Binary image.
+func IsGrayImgBlackAndWhite(i *image.Gray) bool {
+	return isGrayBlackWhite(i)
+}
+
 func blackOrWhite(c, threshold uint8) uint8 {
 	if c < threshold {
 		return 255

internal/jbig2/bitmap/bitmap.go

@@ -545,7 +545,7 @@ func (b *Bitmap) addBorderGeneral(left, right, top, bot int, val int) (*Bitmap,
 
 // addPadBits creates new data byte slice that contains extra padding on the last byte for each row.
 func (b *Bitmap) addPadBits() (err error) {
-	const processName = "addPadBits"
+	const processName = "bitmap.addPadBits"
 	endbits := b.Width % 8
 	if endbits == 0 {
 		// no partial words
@@ -559,18 +559,16 @@ func (b *Bitmap) addPadBits() (err error) {
 	w := writer.NewMSB(data)
 	temp := make([]byte, fullBytes)
 	var (
-		i, j int
+		i    int
 		bits uint64
 	)
 	for i = 0; i < b.Height; i++ {
 		// iterate over full bytes
-		for j = 0; j < fullBytes; j++ {
-			if _, err = r.Read(temp); err != nil {
-				return errors.Wrap(err, processName, "full byte")
-			}
-			if _, err = w.Write(temp); err != nil {
-				return errors.Wrap(err, processName, "full bytes")
-			}
+		if _, err = r.Read(temp); err != nil {
+			return errors.Wrap(err, processName, "full byte")
+		}
+		if _, err = w.Write(temp); err != nil {
+			return errors.Wrap(err, processName, "full bytes")
 		}
 		// read unused bits
 		if bits, err = r.ReadBits(byte(endbits)); err != nil {

internal/jbig2/document/document.go

@@ -98,7 +98,7 @@ func (d *Document) AddGenericPage(bm *bitmap.Bitmap, duplicateLineRemoval bool)
 	const processName = "Document.AddGenericPage"
 	// check if this is PDFMode and there is already a page
 	if !d.FullHeaders && d.NumberOfPages != 0 {
-		return errors.Error(processName, "document already contains page. FileMode disallows addoing more than one page")
+		return errors.Error(processName, "document already contains page. FileMode disallows adding more than one page")
 	}
 	// initialize page
 	page := &Page{

internal/jbig2/tests/.gitignore

@@ -3,3 +3,4 @@ jbig2files
 .test
 *.jbig2
 .envrc
+.env

internal/jbig2/tests/encode_pdf_test.go

@@ -0,0 +1,155 @@
+/*
+ * This file is subject to the terms and conditions defined in
+ * file 'LICENSE.md', which is part of this source code package.
+ */
+
+package tests
+
+import (
+	"bytes"
+	"crypto/md5"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/unidoc/unipdf/v3/common"
+	"github.com/unidoc/unipdf/v3/core"
+	"github.com/unidoc/unipdf/v3/creator"
+)
+
+// TestImageEncodeJBIG2PDF tests the encode process for the JBIG2 encoder into PDF file.
+func TestImageEncodeJBIG2PDF(t *testing.T) {
+	dirName := os.Getenv(EnvImageDirectory)
+	if dirName == "" {
+		t.Skipf("no environment variable: '%s' provided", EnvImageDirectory)
+	}
+
+	// get the file names within given directory
+	fileNames, err := readFileNames(dirName, "jpg")
+	require.NoError(t, err)
+
+	if len(fileNames) == 0 {
+		t.Skipf("no files found in the '%s' directory", dirName)
+	}
+
+	// prepare temporary directory where the jbig2 files would be stored
+	tempDir := filepath.Join(os.TempDir(), "unipdf", "jbig2", "encoded-pdf")
+	err = os.MkdirAll(tempDir, 0700)
+	require.NoError(t, err)
+
+	var f *os.File
+	switch {
+	case logToFile:
+		fileName := filepath.Join(tempDir, fmt.Sprintf("log_%s.txt", time.Now().Format("20060102")))
+		f, err = os.Create(fileName)
+		require.NoError(t, err)
+		common.SetLogger(common.NewWriterLogger(common.LogLevelTrace, f))
+	case testing.Verbose():
+		common.SetLogger(common.NewConsoleLogger(common.LogLevelDebug))
+	}
+
+	// clear all the temporary files
+	defer func() {
+		if f != nil {
+			f.Close()
+		}
+
+		switch {
+		case !keepEncodedFile && !logToFile:
+			err = os.RemoveAll(filepath.Join(tempDir))
+		case !keepEncodedFile:
+			err = filepath.Walk(tempDir, func(path string, info os.FileInfo, err error) error {
+				if err != nil {
+					return err
+				}
+				if strings.HasSuffix(info.Name(), "zip") {
+					return os.Remove(path)
+				}
+				return nil
+			})
+		}
+		if err != nil {
+			common.Log.Error(err.Error())
+		}
+	}()
+
+	defer func() {
+		if !keepEncodedFile {
+			os.RemoveAll(tempDir)
+		}
+	}()
+
+	buf := &bytes.Buffer{}
+	h := md5.New()
+	edp := []goldenValuePair{}
+
+	for _, fileName := range fileNames {
+		var duplicateLinesRemoval bool
+		duplicateLinesName := "NoDuplicateLinesRemoval"
+		for i := 0; i < 2; i++ {
+			if i == 1 {
+				duplicateLinesRemoval = true
+				duplicateLinesName = duplicateLinesName[2:]
+			}
+			t.Run(rawFileName(fileName)+duplicateLinesName, func(t *testing.T) {
+				// read the file
+				c := creator.New()
+
+				img, err := c.NewImageFromFile(filepath.Join(dirName, fileName))
+				require.NoError(t, err)
+
+				// conver an image to binary image
+				err = img.ConvertToBinary()
+				require.NoError(t, err)
+
+				img.ScaleToWidth(612.0)
+
+				e := core.NewJBIG2Encoder()
+				if duplicateLinesRemoval {
+					e.DefaultPageSettings.DuplicatedLinesRemoval = true
+				}
+				img.SetEncoder(e)
+
+				// Use page width of 612 points, and calculate the height proportionally based on the image.
+				// Standard PPI is 72 points per inch, thus a width of 8.5"
+				height := 612.0 * img.Height() / img.Width()
+				c.NewPage()
+				c.SetPageSize(creator.PageSize{612, height})
+				// c.SetPageSize(creator.PageSize{img.Width() * 1.2, img.Height() * 1.2})
+				img.SetPos(0, 0)
+
+				err = c.Draw(img)
+				require.NoError(t, err)
+
+				err = c.Write(buf)
+				require.NoError(t, err)
+
+				_, err = h.Write(buf.Bytes())
+				require.NoError(t, err)
+
+				if keepEncodedFile {
+					f, err := os.Create(filepath.Join(tempDir, rawFileName(fileName)+duplicateLinesName+".pdf"))
+					require.NoError(t, err)
+					defer f.Close()
+
+					_, err = f.Write(buf.Bytes())
+					require.NoError(t, err)
+				}
+				hashEncoded := h.Sum(nil)
+				buf.Reset()
+
+				edp = append(edp, goldenValuePair{
+					Filename: rawFileName(fileName) + duplicateLinesName,
+					Hash:     hashEncoded,
+				})
+			})
+		}
+	}
+	const goldenFileName = "encoded-pdf"
+	checkGoldenValuePairs(t, dirName, goldenFileName, edp...)
+}

model/image.go

@@ -11,14 +11,15 @@ import (
 	goimage "image"
 	gocolor "image/color"
 	"image/draw"
-	"io"
-
 	// Imported for initialization side effects.
 	_ "image/gif"
 	_ "image/png"
+	"io"
 
 	"github.com/unidoc/unipdf/v3/common"
 	"github.com/unidoc/unipdf/v3/core"
+	"github.com/unidoc/unipdf/v3/internal/imageutil"
+	"github.com/unidoc/unipdf/v3/internal/jbig2/bitmap"
 	"github.com/unidoc/unipdf/v3/internal/sampling"
 )
 
@@ -50,6 +51,59 @@ func (img *Image) AlphaMap(mapFunc AlphaMapFunc) {
 	}
 }
 
+// ConvertToBinary converts current image into binary (bi-level) format.
+// Binary images are composed of single bits per pixel (only black or white).
+// If provided image has more color components, then it would be converted into binary image using
+// histogram auto threshold function.
+func (img *Image) ConvertToBinary() error {
+	// check if  given image is already a binary image (1 bit per component - 1 color component - the size of the data
+	// is equal to the multiplication of width and height.
+	if img.ColorComponents == 1 && img.BitsPerComponent == 1 {
+		return nil
+	}
+	i, err := img.ToGoImage()
+	if err != nil {
+		return err
+	}
+	gray := imageutil.ImgToGray(i)
+	// check if 'img' is already a binary image.
+	if !imageutil.IsGrayImgBlackAndWhite(gray) {
+		threshold := imageutil.AutoThresholdTriangle(imageutil.GrayImageHistogram(gray))
+		gray = imageutil.ImgToBinary(i, threshold)
+	}
+	// use JBIG2 bitmap as the temporary binary data converter - by default it uses
+	tmpBM := bitmap.New(int(img.Width), int(img.Height))
+	for y := 0; y < tmpBM.Height; y++ {
+		for x := 0; x < tmpBM.Width; x++ {
+			c := gray.GrayAt(x, y)
+			// set only the white pixel - c.Y != 0
+			if c.Y != 0 {
+				if err = tmpBM.SetPixel(x, y, 1); err != nil {
+					return err
+				}
+			}
+		}
+	}
+	unpaddedData, err := tmpBM.GetUnpaddedData()
+	if err != nil {
+		return err
+	}
+	img.BitsPerComponent = 1
+	img.ColorComponents = 1
+	img.Data = unpaddedData
+	return nil
+}
+
+// GetParamsDict returns *core.PdfObjectDictionary with a set of basic image parameters.
+func (img *Image) GetParamsDict() *core.PdfObjectDictionary {
+	params := core.MakeDict()
+	params.Set("Width", core.MakeInteger(img.Width))
+	params.Set("Height", core.MakeInteger(img.Height))
+	params.Set("ColorComponents", core.MakeInteger(int64(img.ColorComponents)))
+	params.Set("BitsPerComponent", core.MakeInteger(img.BitsPerComponent))
+	return params
+}
+
 // GetSamples converts the raw byte slice into samples which are stored in a uint32 bit array.
 // Each sample is represented by BitsPerComponent consecutive bits in the raw data.
 // NOTE: The method resamples the image byte data before returning the result and
@@ -294,6 +348,15 @@ func (img *Image) Resample(targetBitsPerComponent int64) {
 	img.BitsPerComponent = int64(targetBitsPerComponent)
 }
 
+// ToJBIG2Image converts current image to the core.JBIG2Image.
+func (img *Image) ToJBIG2Image() (*core.JBIG2Image, error) {
+	goImg, err := img.ToGoImage()
+	if err != nil {
+		return nil, err
+	}
+	return core.GoImageToJBIG2(goImg, core.JB2ImageAutoThreshold)
+}
+
 // ToGoImage converts the unidoc Image to a golang Image structure.
 func (img *Image) ToGoImage() (goimage.Image, error) {
 	common.Log.Trace("Converting to go image")

model/xobject.go

@@ -240,20 +240,17 @@ func NewXObjectImageFromImage(img *Image, cs PdfColorspace, encoder core.StreamE
 // If `encoder` is nil, uses raw encoding (none).
 func UpdateXObjectImageFromImage(xobjIn *XObjectImage, img *Image, cs PdfColorspace,
 	encoder core.StreamEncoder) (*XObjectImage, error) {
-	xobj := NewXObjectImage()
-
 	if encoder == nil {
 		encoder = core.NewRawEncoder()
 	}
+	encoder.UpdateParams(img.GetParamsDict())
 
 	encoded, err := encoder.EncodeBytes(img.Data)
 	if err != nil {
 		common.Log.Debug("Error with encoding: %v", err)
 		return nil, err
 	}
-
-	xobj.Filter = encoder
-	xobj.Stream = encoded
+	xobj := NewXObjectImage()
 
 	// Width and height.
 	imWidth := img.Width
@@ -261,8 +258,12 @@ func UpdateXObjectImageFromImage(xobjIn *XObjectImage, img *Image, cs PdfColorsp
 	xobj.Width = &imWidth
 	xobj.Height = &imHeight
 
-	// Bits.
-	xobj.BitsPerComponent = &img.BitsPerComponent
+	// Bits per Component.
+	imBPC := img.BitsPerComponent
+	xobj.BitsPerComponent = &imBPC
+
+	xobj.Filter = encoder
+	xobj.Stream = encoded
 
 	// Guess colorspace if not explicitly set.
 	if cs == nil {
@@ -284,6 +285,7 @@ func UpdateXObjectImageFromImage(xobjIn *XObjectImage, img *Image, cs PdfColorsp
 		// Has same width and height as original and stored in same
 		// bits per component (1 component, hence the DeviceGray channel).
 		smask := NewXObjectImage()
+
 		smask.Filter = encoder
 		encoded, err := encoder.EncodeBytes(img.alphaData)
 		if err != nil {
@@ -291,7 +293,7 @@ func UpdateXObjectImageFromImage(xobjIn *XObjectImage, img *Image, cs PdfColorsp
 			return nil, err
 		}
 		smask.Stream = encoded
-		smask.BitsPerComponent = &img.BitsPerComponent
+		smask.BitsPerComponent = xobj.BitsPerComponent
 		smask.Width = &img.Width
 		smask.Height = &img.Height
 		smask.ColorSpace = NewPdfColorspaceDeviceGray()
@@ -448,6 +450,8 @@ func NewXObjectImageFromStream(stream *core.PdfObjectStream) (*XObjectImage, err
 
 // SetImage updates XObject Image with new image data.
 func (ximg *XObjectImage) SetImage(img *Image, cs PdfColorspace) error {
+	// update image parameters of the filter encoder.
+	ximg.Filter.UpdateParams(img.GetParamsDict())
 	encoded, err := ximg.Filter.EncodeBytes(img.Data)
 	if err != nil {
 		return err
@@ -493,6 +497,7 @@ func (ximg *XObjectImage) SetFilter(encoder core.StreamEncoder) error {
 	}
 
 	ximg.Filter = encoder
+	encoder.UpdateParams(ximg.getParamsDict())
 	encoded, err = encoder.EncodeBytes(decoded)
 	if err != nil {
 		return err
@@ -596,3 +601,13 @@ func (ximg *XObjectImage) ToPdfObject() core.PdfObject {
 
 	return stream
 }
+
+// getParamsDict returns *core.PdfObjectDictionary with a set of basic image parameters.
+func (ximg *XObjectImage) getParamsDict() *core.PdfObjectDictionary {
+	params := core.MakeDict()
+	params.Set("Width", core.MakeInteger(*ximg.Width))
+	params.Set("Height", core.MakeInteger(*ximg.Height))
+	params.Set("ColorComponents", core.MakeInteger(int64(ximg.ColorSpace.GetNumComponents())))
+	params.Set("BitsPerComponent", core.MakeInteger(*ximg.BitsPerComponent))
+	return params
+}