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IDProjectCategoryView StatusLast Update
0017608ScribusPDFpublic2025-08-29 07:19
Reportermaximilian Assigned To 
PrioritynormalSeveritymajorReproducibilityalways
Status newResolutionopen 
Platformx64OSWindowsOS Version10 Home 64-bit
Product Version1.6.4 
Summary0017608: Incorrect blending color space assigned to objects in generated PDF file intended for printer
DescriptionWhen exporting a Scribus document containing objects in a layer with a blend mode other than „normal“ to a PDF/X-4 file, the blending color space of the corresponding objects in the PDF file will be set to the document’s output intent (a CMYK color profile) instead of the color space in which Scribus blends the colors, which seems to be one of the two document’s RGB color profiles. Depending on the blend mode used, this can cause the blend’s result colors in the PDF document to be noticeably different from the colors displayed in the Scribus document, even when taking the expected conversion of the visible color from RGB to CMYK into account.

I have only tried this with exclusion blend mode, but I suppose it is the same for other blend modes. The problem also seems to occur when choosing not a PDF/X version as the desired format, but simply PDF 1.4 or higher and manually choosing "printer" as the document's intended output.
Steps To ReproduceMake a new Scribus document.
Enable color management and define a color profile for printing.
Create an object in the default layer.
Create a second layer, configure a blending mode for this layer and ensure that this layer is placed before the first layer.
Create an object in the second layer and place it in front of the first object.
Export the document to a PDF/X-4 file.
Additional InformationTo demonstrate this problem, I have attached a sample document containing the same text three times in a row. The middle text is in a layer with the blend mode set to exclusion, the first and the third text are in a layer without a blend mode. The first text has its color hardcoded to the color that would result from the second text's blend being performed in RGB space, and the third text has the color hardcoded that would result from the blend being performed in a CMYK blending color space (I used the blend formula in this PDF 1.6 reference: https://printtechnologies.org/standards/files/pdf-reference-1.6-addendum-blend-modes.pdf; see the attached ods file for the color calculations I performed for this document).

I have also attached the PDF/X-4 file generated from this document by Scribus. It is rendered correctly in the desktop version of Acrobat Reader, but not in the mobile version (this is an intended limitation of the mobile version, see https://community.adobe.com/t5/acrobat-reader-mobile-discussions/probable-bug-color-blend-with-cmyk-blending-color-space-rendered-incorrectly-on-iphone/m-p/15476006), so the effect of the bug can only be observed when viewing the PDF file in a desktop version of Acrobat Reader or Acrobat. I included a screenshot of how the file is rendered in the desktop version of Acrobat Reader for the sake of completeness.
Tagscolor, colors, export to PDF, pdf export
PatchNo

Activities

maximilian

2025-08-26 16:53

reporter  

Color calculations.ods (17,484 bytes)
Sample document.pdf (793,507 bytes)
Sample document.sla (20,720 bytes)   
<?xml version="1.0" encoding="UTF-8"?>
<SCRIBUSUTF8NEW Version="1.6.4">
    <DOCUMENT ANZPAGES="1" PAGEWIDTH="595.275590551181" PAGEHEIGHT="841.889763779528" BORDERLEFT="40" BORDERRIGHT="40" BORDERTOP="40" BORDERBOTTOM="40" PRESET="0" BleedTop="0" BleedLeft="0" BleedRight="0" BleedBottom="0" ORIENTATION="0" PAGESIZE="A4" FIRSTNUM="1" BOOK="0" AUTOSPALTEN="1" ABSTSPALTEN="11" UNITS="1" DFONT="Arial Regular" DSIZE="12" DCOL="1" DGAP="0" TabFill="" TabWidth="36" TextDistLeft="0" TextDistRight="0" TextDistBottom="0" TextDistTop="0" FirstLineOffset="1" AUTHOR="" COMMENTS="" KEYWORDS="" PUBLISHER="" DOCDATE="" DOCTYPE="" DOCFORMAT="" DOCIDENT="" DOCSOURCE="" DOCLANGINFO="" DOCRELATION="" DOCCOVER="" DOCRIGHTS="" DOCCONTRIB="" TITLE="" SUBJECT="" VHOCH="33" VHOCHSC="66" VTIEF="33" VTIEFSC="66" VKAPIT="75" BASEGRID="14.4" BASEO="0" AUTOL="100" UnderlinePos="-1" UnderlineWidth="-1" StrikeThruPos="-1" StrikeThruWidth="-1" GROUPC="1" HCMS="1" DPSo="0" DPSFo="0" DPuse="1" DPgam="0" DPbla="1" DPPr="ISO Coated v2 300% (basICColor)" DPIn="sRGB display profile (ICC v2.2)" DPInCMYK="ISO Coated v2 300% (basICColor)" DPIn2="sRGB display profile (ICC v2.2)" DPIn3="ISO Coated v2 300% (basICColor)" DISc="1" DIIm="0" ALAYER="2" LANGUAGE="en_GB" AUTOMATIC="1" AUTOCHECK="0" GUIDELOCK="0" SnapToGuides="0" SnapToGrid="0" SnapToElement="0" MINGRID="20.0012598425197" MAJGRID="100.00062992126" SHOWGRID="0" SHOWGUIDES="1" showcolborders="1" SHOWFRAME="1" SHOWControl="0" SHOWLAYERM="0" SHOWMARGIN="1" SHOWBASE="0" SHOWPICT="1" SHOWLINK="0" rulerMode="1" showrulers="1" showBleed="1" rulerXoffset="0" rulerYoffset="0" GuideRad="10" GRAB="4" POLYC="4" POLYF="0.502045814642449" POLYR="0" POLYIR="0" POLYCUR="0" POLYOCUR="0" POLYS="0" arcStartAngle="30" arcSweepAngle="300" spiralStartAngle="0" spiralEndAngle="1080" spiralFactor="1.2" AutoSave="1" AutoSaveTime="600000" AutoSaveCount="1" AutoSaveKeep="0" AUtoSaveInDocDir="1" AutoSaveDir="" ScratchBottom="20.0012598425197" ScratchLeft="100.00062992126" ScratchRight="100.00062992126" ScratchTop="20.0012598425197" GapHorizontal="0" GapVertical="39.9996850393701" StartArrow="0" EndArrow="0" PEN="Black" BRUSH="None" PENLINE="Black" PENTEXT="Black" StrokeText="Black" TextBackGround="None" TextLineColor="None" TextBackGroundShade="100" TextLineShade="100" TextPenShade="100" TextStrokeShade="100" STIL="1" STILLINE="1" WIDTH="1" WIDTHLINE="1" PENSHADE="100" LINESHADE="100" BRUSHSHADE="100" CPICT="None" PICTSHADE="100" CSPICT="None" PICTSSHADE="100" PICTSCX="1" PICTSCY="1" PSCALE="1" PASPECT="1" EmbeddedPath="0" HalfRes="1" dispX="10.0006299212598" dispY="10.0006299212598" constrain="15" MINORC="#00ff00" MAJORC="#00ff00" GuideC="#000080" BaseC="#c0c0c0" renderStack="2 0 4 1 3" GridType="0" PAGEC="#ffffff" MARGC="#0000ff" RANDF="0" currentProfile="PDF 1.4" calligraphicPenFillColor="Black" calligraphicPenLineColor="Black" calligraphicPenFillColorShade="100" calligraphicPenLineColorShade="100" calligraphicPenLineWidth="1" calligraphicPenAngle="0" calligraphicPenWidth="10" calligraphicPenStyle="1">
        <CheckProfile Name="PDF 1.3" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="1" minResolution="144" maxResolution="2400" checkAnnotations="0" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="0" checkDeviceColorsAndOutputIntent="0" checkFontNotEmbedded="1" checkFontIsOpenType="1" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <CheckProfile Name="PDF 1.4" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="0" minResolution="144" maxResolution="2400" checkAnnotations="0" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="0" checkDeviceColorsAndOutputIntent="0" checkFontNotEmbedded="1" checkFontIsOpenType="1" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <CheckProfile Name="PDF 1.5" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="0" minResolution="144" maxResolution="2400" checkAnnotations="0" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="0" checkDeviceColorsAndOutputIntent="0" checkFontNotEmbedded="1" checkFontIsOpenType="1" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <CheckProfile Name="PDF 1.6" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="0" minResolution="144" maxResolution="2400" checkAnnotations="0" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="0" checkDeviceColorsAndOutputIntent="0" checkFontNotEmbedded="1" checkFontIsOpenType="0" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <CheckProfile Name="PDF/X-1a" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="1" minResolution="144" maxResolution="2400" checkAnnotations="1" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="1" checkDeviceColorsAndOutputIntent="0" checkFontNotEmbedded="1" checkFontIsOpenType="1" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <CheckProfile Name="PDF/X-3" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="1" minResolution="144" maxResolution="2400" checkAnnotations="1" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="0" checkDeviceColorsAndOutputIntent="1" checkFontNotEmbedded="1" checkFontIsOpenType="1" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <CheckProfile Name="PDF/X-4" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="0" minResolution="144" maxResolution="2400" checkAnnotations="1" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="0" checkDeviceColorsAndOutputIntent="1" checkFontNotEmbedded="1" checkFontIsOpenType="0" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <CheckProfile Name="PostScript" ignoreErrors="0" autoCheck="1" checkGlyphs="1" checkOrphans="1" checkOverflow="1" checkPictures="1" checkPartFilledImageFrames="0" checkResolution="1" checkTransparency="1" minResolution="144" maxResolution="2400" checkAnnotations="0" checkRasterPDF="1" checkForGIF="1" ignoreOffLayers="0" checkNotCMYKOrSpot="0" checkDeviceColorsAndOutputIntent="0" checkFontNotEmbedded="0" checkFontIsOpenType="0" checkAppliedMasterDifferentSide="1" checkEmptyTextFrames="1"/>
        <COLOR NAME="Black" SPACE="CMYK" C="0" M="0" Y="0" K="100"/>
        <COLOR NAME="Blue" SPACE="RGB" R="0" G="0" B="255"/>
        <COLOR NAME="Blue dark" SPACE="RGB" R="0" G="0" B="13"/>
        <COLOR NAME="Blue dark CMYK" SPACE="CMYK" C="81.2710765239948" M="73.8826581216144" Y="51.5465018692302" K="87.2312504768444"/>
        <COLOR NAME="Cool Black" SPACE="CMYK" C="60" M="0" Y="0" K="100"/>
        <COLOR NAME="Cyan" SPACE="CMYK" C="100" M="0" Y="0" K="0"/>
        <COLOR NAME="Green" SPACE="RGB" R="0" G="255" B="0"/>
        <COLOR NAME="Magenta" SPACE="CMYK" C="0" M="100" Y="0" K="0"/>
        <COLOR NAME="Red" SPACE="RGB" R="255" G="0" B="0"/>
        <COLOR NAME="Registration" SPACE="CMYK" C="100" M="100" Y="100" K="100" Register="1"/>
        <COLOR NAME="Rich Black" SPACE="CMYK" C="60" M="40" Y="40" K="100"/>
        <COLOR NAME="Warm Black" SPACE="CMYK" C="0" M="60" Y="29.8039215686275" K="100"/>
        <COLOR NAME="White" SPACE="CMYK" C="0" M="0" Y="0" K="0"/>
        <COLOR NAME="Yellow" SPACE="CMYK" C="0" M="0" Y="100" K="0"/>
        <COLOR NAME="Yellow pale" SPACE="RGB" R="243" G="243" B="169"/>
        <COLOR NAME="Yellow pale CMYK" SPACE="CMYK" C="7.55779354543374" M="0.439459830624857" Y="44.2084382391089" K="0"/>
        <COLOR NAME="Yellow pale after CMYK-exclusion flattened" SPACE="CMYK" C="23.5" M="26.3" Y="49.8" K="12.8"/>
        <COLOR NAME="Yellow pale after RGB-exclusion flattened" SPACE="RGB" R="243" G="243" B="165"/>
        <HYPHEN/>
        <CHARSTYLE CNAME="Default Character Style" DefaultStyle="1" FONT="Arial Regular" FONTSIZE="12" FONTFEATURES="" FEATURES="inherit" FCOLOR="Black" FSHADE="100" HyphenWordMin="3" SCOLOR="Black" BGCOLOR="None" BGSHADE="100" SSHADE="100" TXTSHX="5" TXTSHY="-5" TXTOUT="1" TXTULP="-0.1" TXTULW="-0.1" TXTSTP="-0.1" TXTSTW="-0.1" SCALEH="100" SCALEV="100" BASEO="0" KERN="0" LANGUAGE="en_GB"/>
        <STYLE NAME="Default Paragraph Style" DefaultStyle="1" ALIGN="0" DIRECTION="0" LINESPMode="0" LINESP="15" INDENT="0" RMARGIN="0" FIRST="0" VOR="0" NACH="0" ParagraphEffectOffset="0" DROP="0" DROPLIN="2" Bullet="0" Numeration="0" HyphenConsecutiveLines="2" BCOLOR="None" BSHADE="100"/>
        <TableStyle NAME="Default Table Style" DefaultStyle="1" FillColor="None" FillShade="100">
            <TableBorderLeft>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderLeft>
            <TableBorderRight>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderRight>
            <TableBorderTop>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderTop>
            <TableBorderBottom>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderBottom>
        </TableStyle>
        <CellStyle NAME="Default Cell Style" DefaultStyle="1" FillColor="None" FillShade="100" LeftPadding="1" RightPadding="1" TopPadding="1" BottomPadding="1">
            <TableBorderLeft>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderLeft>
            <TableBorderRight>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderRight>
            <TableBorderTop>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderTop>
            <TableBorderBottom>
                <TableBorderLine Width="1" PenStyle="1" Color="Black" Shade="100"/>
            </TableBorderBottom>
        </CellStyle>
        <LAYERS NUMMER="0" LEVEL="0" NAME="Background" SICHTBAR="1" DRUCKEN="1" EDIT="1" SELECT="1" FLOW="1" TRANS="1" BLEND="0" OUTL="0" LAYERC="#000000"/>
        <LAYERS NUMMER="1" LEVEL="2" NAME="Text with blend mode" SICHTBAR="1" DRUCKEN="1" EDIT="1" SELECT="1" FLOW="1" TRANS="1" BLEND="9" OUTL="0" LAYERC="#ff0000"/>
        <LAYERS NUMMER="2" LEVEL="1" NAME="Text without blend mode" SICHTBAR="1" DRUCKEN="1" EDIT="1" SELECT="1" FLOW="1" TRANS="1" BLEND="0" OUTL="0" LAYERC="#00ff00"/>
        <Printer firstUse="1" toFile="0" useAltPrintCommand="0" outputSeparations="0" useSpotColors="1" useColor="1" mirrorH="0" mirrorV="0" useICC="1" doGCR="0" doClip="0" setDevParam="0" useDocBleeds="1" cropMarks="0" bleedMarks="0" registrationMarks="0" colorMarks="0" includePDFMarks="1" PSLevel="3" PrintEngine="4" markLength="20.0013" markOffset="0" BleedTop="0" BleedLeft="0" BleedRight="0" BleedBottom="0" printer="HP5AC57F.home (HP ENVY 5000 series)" filename="" separationName="All" printerCommand=""/>
        <PDF firstUse="0" Thumbnails="0" Articles="0" Bookmarks="0" Compress="1" CMethod="0" Quality="0" EmbedPDF="0" MirrorH="0" MirrorV="0" Clip="0" rangeSel="0" rangeTxt="" RotateDeg="0" PresentMode="0" RecalcPic="0" FontEmbedding="0" Grayscale="0" RGBMode="0" UseProfiles="0" UseProfiles2="1" Binding="0" PicRes="300" Resolution="300" Version="16" Intent="1" Intent2="0" SolidP="sRGB display profile (ICC v2.2)" ImageP="sRGB display profile (ICC v2.2)" PrintP="ISO Coated v2 300% (basICColor)" InfoString="Sample document.sla" BTop="0" BLeft="0" BRight="0" BBottom="0" useDocBleeds="1" cropMarks="0" bleedMarks="0" registrationMarks="0" colorMarks="0" docInfoMarks="0" markLength="20.0012598425197" markOffset="0" ImagePr="0" PassOwner="" PassUser="" Permissions="-4" Encrypt="0" UseLayers="0" UseLpi="0" UseSpotColors="1" doMultiFile="0" displayBookmarks="0" displayFullscreen="0" displayLayers="0" displayThumbs="0" hideMenuBar="0" hideToolBar="0" fitWindow="0" openAfterExport="0" PageLayout="0" openAction="">
            <Subset Name="Liberation Sans Bold"/>
            <LPI Color="" Frequency="133" Angle="45" SpotFunction="3"/>
            <LPI Color="Black" Frequency="133" Angle="45" SpotFunction="3"/>
            <LPI Color="Cyan" Frequency="133" Angle="105" SpotFunction="3"/>
            <LPI Color="Magenta" Frequency="133" Angle="75" SpotFunction="3"/>
            <LPI Color="Yellow" Frequency="133" Angle="90" SpotFunction="3"/>
        </PDF>
        <DocItemAttributes/>
        <TablesOfContents/>
        <NotesStyles>
            <notesStyle Name="Default" Start="1" Endnotes="0" Type="Type_1_2_3" Range="0" Prefix="" Suffix=")" AutoHeight="1" AutoWidth="1" AutoRemove="1" AutoWeld="1" SuperNote="1" SuperMaster="1" MarksStyle="" NotesStyle=""/>
        </NotesStyles>
        <PageSets>
            <Set Name="Single Page" FirstPage="0" Rows="1" Columns="1"/>
            <Set Name="Facing Pages" FirstPage="1" Rows="1" Columns="2">
                <PageNames Name="Left Page"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="3-Fold" FirstPage="0" Rows="1" Columns="3">
                <PageNames Name="Left Page"/>
                <PageNames Name="Middle"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="4-Fold" FirstPage="0" Rows="1" Columns="4">
                <PageNames Name="Left Page"/>
                <PageNames Name="Middle Left"/>
                <PageNames Name="Middle Right"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="Single Page" FirstPage="0" Rows="1" Columns="1"/>
            <Set Name="Facing Pages" FirstPage="1" Rows="1" Columns="2">
                <PageNames Name="Left Page"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="3-Fold" FirstPage="0" Rows="1" Columns="3">
                <PageNames Name="Left Page"/>
                <PageNames Name="Middle"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="4-Fold" FirstPage="0" Rows="1" Columns="4">
                <PageNames Name="Left Page"/>
                <PageNames Name="Middle Left"/>
                <PageNames Name="Middle Right"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="Single Page" FirstPage="0" Rows="1" Columns="1"/>
            <Set Name="Facing Pages" FirstPage="1" Rows="1" Columns="2">
                <PageNames Name="Left Page"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="3-Fold" FirstPage="0" Rows="1" Columns="3">
                <PageNames Name="Left Page"/>
                <PageNames Name="Middle"/>
                <PageNames Name="Right Page"/>
            </Set>
            <Set Name="4-Fold" FirstPage="0" Rows="1" Columns="4">
                <PageNames Name="Left Page"/>
                <PageNames Name="Middle Left"/>
                <PageNames Name="Middle Right"/>
                <PageNames Name="Right Page"/>
            </Set>
        </PageSets>
        <Sections>
            <Section Number="0" Name="Section 1" From="0" To="0" Type="Type_1_2_3" Start="1" Reversed="0" Active="1" FillChar="0" FieldWidth="0"/>
        </Sections>
        <MASTERPAGE PAGEXPOS="100.00062992126" PAGEYPOS="20.0012598425197" PAGEWIDTH="595.275590551181" PAGEHEIGHT="841.889763779528" BORDERLEFT="40" BORDERRIGHT="40" BORDERTOP="40" BORDERBOTTOM="40" NUM="0" NAM="Normal" MNAM="" Size="A4" Orientation="0" LEFT="0" PRESET="0" VerticalGuides="" HorizontalGuides="" AGhorizontalAutoGap="0" AGverticalAutoGap="0" AGhorizontalAutoCount="0" AGverticalAutoCount="0" AGhorizontalAutoRefer="0" AGverticalAutoRefer="0" AGSelection="0 0 0 0" pageEffectDuration="1" pageViewDuration="1" effectType="0" Dm="0" M="0" Di="0"/>
        <PAGE PAGEXPOS="100.00062992126" PAGEYPOS="20.0012598425197" PAGEWIDTH="595.275590551181" PAGEHEIGHT="841.889763779528" BORDERLEFT="40" BORDERRIGHT="40" BORDERTOP="40" BORDERBOTTOM="40" NUM="0" NAM="" MNAM="Normal" Size="A4" Orientation="0" LEFT="0" PRESET="0" VerticalGuides="" HorizontalGuides="" AGhorizontalAutoGap="0" AGverticalAutoGap="0" AGhorizontalAutoCount="0" AGverticalAutoCount="0" AGhorizontalAutoRefer="0" AGverticalAutoRefer="0" AGSelection="0 0 0 0" pageEffectDuration="1" pageViewDuration="1" effectType="0" Dm="0" M="0" Di="0"/>
        <PAGEOBJECT XPOS="188.066996625422" YPOS="314.083160854893" OwnPage="0" ItemID="198641840" PTYPE="6" WIDTH="419.142857142857" HEIGHT="342.27398200225" FRTYPE="0" CLIPEDIT="0" PWIDTH="1" PCOLOR="Blue dark" PLINEART="1" path="M0 0 L419.143 0 L419.143 342.274 L0 342.274 L0 0 Z" copath="M0 0 L419.143 0 L419.143 342.274 L0 342.274 L0 0 Z" gXpos="188.066996625422" gYpos="314.083160854893" gWidth="0" gHeight="0" LAYER="0"/>
        <PAGEOBJECT XPOS="231.13842519685" YPOS="526.812705286838" OwnPage="0" ItemID="199491872" PTYPE="4" WIDTH="333" HEIGHT="119.571428571429" FRTYPE="0" CLIPEDIT="0" PWIDTH="1" SHADE="98" PLINEART="1" ANNAME="Text_CMYK_blending_flattened" LOCALSCX="1" LOCALSCY="1" LOCALX="0" LOCALY="0" LOCALROT="0" PICART="1" SCALETYPE="1" RATIO="1" COLUMNS="1" COLGAP="0" AUTOTEXT="0" EXTRA="0" TEXTRA="0" BEXTRA="0" REXTRA="0" VAlign="1" FLOP="1" PLTSHOW="0" BASEOF="0" textPathType="0" textPathFlipped="0" path="M0 0 L333 0 L333 119.571 L0 119.571 L0 0 Z" copath="M0 0 L333 0 L333 119.571 L0 119.571 L0 0 Z" gXpos="2.8421709430404e-14" gYpos="202.75653543307" gWidth="333" gHeight="322.327964004499" LAYER="2" NEXTITEM="-1" BACKITEM="-1">
            <StoryText>
                <DefaultStyle FONT="Liberation Sans Bold" FONTSIZE="56" FCOLOR="Yellow pale after CMYK-exclusion flattened"/>
                <ITEXT FONT="Liberation Sans Bold" FONTSIZE="56" FCOLOR="Yellow pale after CMYK-exclusion flattened" CH="Sample text"/>
                <trail ALIGN="1"/>
            </StoryText>
        </PAGEOBJECT>
        <PAGEOBJECT XPOS="231.13842519685" YPOS="425.434437570303" OwnPage="0" ItemID="5749696" PTYPE="4" WIDTH="333" HEIGHT="119.571428571429" FRTYPE="0" CLIPEDIT="0" PWIDTH="1" SHADE="98" PLINEART="1" LOCALSCX="1" LOCALSCY="1" LOCALX="0" LOCALY="0" LOCALROT="0" PICART="1" SCALETYPE="1" RATIO="1" COLUMNS="1" COLGAP="0" AUTOTEXT="0" EXTRA="0" TEXTRA="0" BEXTRA="0" REXTRA="0" VAlign="1" FLOP="1" PLTSHOW="0" BASEOF="0" textPathType="0" textPathFlipped="0" path="M0 0 L333 0 L333 119.571 L0 119.571 L0 0 Z" copath="M0 0 L333 0 L333 119.571 L0 119.571 L0 0 Z" gXpos="0" gYpos="101.378267716535" gWidth="333" gHeight="322.327964004499" LAYER="1" NEXTITEM="-1" BACKITEM="-1">
            <StoryText>
                <DefaultStyle FONT="Liberation Sans Bold" FONTSIZE="56" FCOLOR="Yellow pale"/>
                <ITEXT FONT="Liberation Sans Bold" FONTSIZE="56" FCOLOR="Yellow pale" CH="Sample text"/>
                <trail ALIGN="1"/>
            </StoryText>
        </PAGEOBJECT>
        <PAGEOBJECT XPOS="231.13842519685" YPOS="324.056169853769" OwnPage="0" ItemID="5653360" PTYPE="4" WIDTH="333" HEIGHT="119.571428571429" FRTYPE="0" CLIPEDIT="0" PWIDTH="1" SHADE="98" PLINEART="1" ANNAME="Text_RGB_blending_flattened" LOCALSCX="1" LOCALSCY="1" LOCALX="0" LOCALY="0" LOCALROT="0" PICART="1" SCALETYPE="1" RATIO="1" COLUMNS="1" COLGAP="0" AUTOTEXT="0" EXTRA="0" TEXTRA="0" BEXTRA="0" REXTRA="0" VAlign="1" FLOP="1" PLTSHOW="0" BASEOF="0" textPathType="0" textPathFlipped="0" path="M0 0 L333 0 L333 119.571 L0 119.571 L0 0 Z" copath="M0 0 L333 0 L333 119.571 L0 119.571 L0 0 Z" gXpos="0" gYpos="0" gWidth="333" gHeight="322.327964004499" LAYER="2" NEXTITEM="-1" BACKITEM="-1">
            <StoryText>
                <DefaultStyle FONT="Liberation Sans Bold" FONTSIZE="56" FCOLOR="Yellow pale after RGB-exclusion flattened"/>
                <ITEXT FONT="Liberation Sans Bold" FONTSIZE="56" FCOLOR="Yellow pale after RGB-exclusion flattened" CH="Sample text"/>
                <trail ALIGN="1"/>
            </StoryText>
        </PAGEOBJECT>
    </DOCUMENT>
</SCRIBUSUTF8NEW>
Sample document.sla (20,720 bytes)   

maximilian

2025-08-27 17:46

reporter   ~0052961

I have just taken a look at the raw data of the PDF file, and it seems to me as if the color space for transparency groups is somehow globally set to DeviceCMYK and the individual transparency groups don't have a color space explicitly assigned to them (I don't really know anything about PDF syntax, though, so this is just my uninformed interpretation of the raw data).

In the case of PDF/X-4, an easy solution would be to simply replace DeviceCMYK here with whatever color space Scribus uses to blend colors (presumably an RGB one), if it is indeed a common color space for all elements in a document, regardless of whether an element is a solid color or an image. If the blending color space used by Scribus depends on whether an element is a solid color or an image, then it would probably be better to assign a color space to the transparency groups individually. But including RGB colors in a PDF/X-4 file is no problem, because a PDF/X-4 permits RGB colors and a PDF/X-4 file contains an output color profile according to which the RGB colors can be converted to the destination color space.

PDF/X-1a does not support transparency anyway and neither does PDF/X-3 (although I am not sure about the latter), so exporting to one of these formats without losing information would not be possible anyway. The question is, what to do when exporting to PDF 1.4 or higher instead of PDF/X-4 and manually choosing printer as intended output. Can a non-X PDF file have a destination color profile embedded just like a PDF/X file? If so, then exporting the document like exporting to PDF/X-4 should be fine. If not, then there is a problem.

jghali

2025-08-27 19:55

administrator   ~0052962

Last edited: 2025-08-27 19:58

The use of a CMYK blending colorspace when exporting to printer target is not an error and fully intentional. Indesign does the same btw : the problem with using a RGB blending colorspace comes from color conversions which occur when colors have to be converted from RGB to CMYK. The main problem comes from black text, I mean here CMYK black text using only black ink. Due to the way ICC color conversions works, there is a high risk that black text won't be K only anymore after conversion if using a RGB blending colorspace, and for professional printers this is bad : more important press setup time, text which looks fatter, more important ink usage, etc...

maximilian

2025-08-27 20:03

reporter   ~0052963

If this is intentional, then it is also intentional that the exported PDF does not reflect the original colors at all, making blending modes in Scribus practically useless when generating a file intended for printing. Apart from that, I don't quite understand what you mean. Does Scribus not perform color conversions in RGB? Because if it does, why should the result color be any different if the PDF file uses the same blending color space?

maximilian

2025-08-27 20:17

reporter   ~0052964

And regarding your comment about InDesign: I don't have InDesign myself, but I have posted about this problem in the Adobe Community because I originally thought that Acrobat Reader displays the PDF file incorrectly, and someone from Adobe recommended to "export as PDF/X-4 with 'Preserve RGB Numbers' where possible." So apparently, InDesign does include an option to preserve RGB colors even when exporting to PDF/X-4.

OK, now I think I understand what you mean. Is it that you fear converting colors that were already CMYK in the original Scribus document to an RGB blending color space in the PDF file? This can be easily remedied if the transparency blending color space is set to RBG only for objects that were already RGB in the original Scribus document. This would not solve the problem that CMYK colors in Scribus are apparently still blended in an RGB color space, but it would at least prevent the problem you mentioned.

jghali

2025-08-27 20:21

administrator   ~0052965

>> If this is intentional, then it is also intentional that the exported PDF does not reflect the original colors at all, making blending modes in Scribus practically useless when generating a file intended for printing.

The color differences which occur when switching from a RGB to a CMYK blending modes is a know "issue" of blending modes in general. In the end when printing, colors will be converted to CMYK anyway. Using a RGB blending mode when exporting would give a wrong impression of the output as CMYK colorspace are typically reduced compared to RGB colorspaces.

>> Does Scribus not perform color conversions in RGB?

When exporting to printer target, the default options will convert colors to CMYK. And the conversion from RGB to CMYK will usually cause color differences because, as already mentionned above, a CMYK printer colorspace is reduced compared to a screen RGB colorspaces.

maximilian

2025-08-27 20:23

reporter   ~0052966

And about your remark that converting a CMYK color to an RGB blending space could turn black-only colors into 4-channel-colors:

Setting up a CMYK blending color space might preserve the black-only property of the color, but on the other hand, it might yield a noticeably different result color in the resulting PDF, which I think is not really desirable. The solution to this problem would be to make Scribus perform blends of CMYK colors in a CMYK color space, instead of an RGB color space, as seems to be the case right now.

maximilian

2025-08-27 20:32

reporter   ~0052967

>> In the end when printing, colors will be converted to CMYK anyway.

This is true, but as my sample document demonstrates, there can be a huge difference between converting both source and backdrop color (both originally RGB) to the target CMYK color space and then performing the blend in that CMYK color space, and performing the blend in the original RGB color space and only converting the result color to the target CMYK space, which is done anyway by PDF/X-4 automatically. The latter method would yield a color much closer to the color displayed in the original Scribus document and therefore closer to the user expectations than the former method.

>> Using a RGB blending mode when exporting would give a wrong impression of the output as CMYK colorspace are typically reduced compared to RGB colorspaces.

I don't follow. What do you mean by "wrong impression"? The impression a user gets when looking at the generated PDF file on a computer screen? Is it not the responsibility of the PDF viewing program to convert the blend's result color to the document's destination color space before displaying it to the user when dealing with a PDF/X-4 file?

maximilian

2025-08-27 20:39

reporter   ~0052968

And if I understood your remark about giving a wrong impression correctly, then why are images exported to the PDF file with their original color profile, even if it is RGB? Perhaps I misunderstood you, but I actually don't see any benefit in explicitly converting RGB colors to the destination color space at all if the PDF contains an output intent profile anyway, because it would be the responsibility of the PDF viewer/ the printer to convert all colors to the destination color space.

jghali

2025-08-27 20:41

administrator   ~0052969

>> someone from Adobe recommended to "export as PDF/X-4 with 'Preserve RGB Numbers' where possible." So apparently, InDesign does include an option to preserve RGB colors even when exporting to PDF/X-4

Yep, RGB colors can be indeed preserved when exporting to PDF/X-4, but the blending colorspace will be defined to a CMYK colorspace anyway.

>> Is it that you fear converting colors that were already CMYK in the original Scribus document to an RGB blending color space in the PDF file?

Yeah, round trips from CMYK -> RGB -> CMYK are pretty bad as ICC color conversions do not offer any guarantee that such round trip works, and in fact such round trip will rarely work.

>> This can be easily remedied if the transparency blending color space is set to RBG only for objects that were already RGB in the original Scribus document.

No, it's not easy : in PDF transparency blending color space is defined for groups of objects, not for individual objects. Blending color space is defined on PDF objects called transparency groups, note the word "groups".

maximilian

2025-08-27 20:54

reporter   ~0052970

>> Yep, RGB colors can be indeed preserved when exporting to PDF/X-4, but the blending colorspace will be defined to a CMYK colorspace anyway.

Are you sure about this? Here is the full context of the sentence I quoted:

"Recommended Solution:

Check the Blend Color Space in the authoring app (Scribus, InDesign, etc.): If your design intent was RGB blending, set the transparency/blend space explicitly to RGB. Export as PDF/X-4 with 'Preserve RGB Numbers' where possible.

Verify in Acrobat Pro Preflight: Open your PDF in Acrobat Pro → Print Production > Output Preview. Check transparency and blend spaces for the text objects.

If needed, force RGB blend space: In Scribus or your source tool, ensure the 'Transparency Blend Space' is set to RGB before exporting. Or export to PDF/X-4 with explicit RGB transparency, then let the printer handle conversion to CMYK."

To me, this sounds like there is an option in InDesign to also preserve RGB transparencies. But I may be wrong.

>> No, it's not easy : in PDF transparency blending color space is defined for groups of objects, not for individual objects. Blending color space is defined on PDF objects called transparency groups, note the word "groups".

By "easy", I meant easy to comprehend, not easy to implement. Of course, I have no idea how difficult it is to implement this.

jghali

2025-08-27 20:54

administrator   ~0052971

>> This is true, but as my sample document demonstrates, there can be a huge difference between converting both source and backdrop color (both originally RGB) to the target CMYK color space and then performing the blend in that CMYK color space, and performing the blend in the original RGB color space and only converting the result color to the target CMYK space, which is done anyway by PDF/X-4 automatically.

The difference of results between using an RGB blending color space and a CMYK blending colorspace should not be a surprise. As I mentionned previously the color differences resulting from switching from a RGB to a CMYK blending modes is a know "issue" of blending modes in general.

No, PDF/X-4 does not do that automatically : this is the PDF viewer or the printer RIPs which does it. And as I mentionned, blending CMYK colors using an RGB blending colorspace then converting back to CMYK for printing, is usually a no go production wise, especially for black text.

maximilian

2025-08-27 21:17

reporter   ~0052972

>> No, it's not easy : in PDF transparency blending color space is defined for groups of objects, not for individual objects. Blending color space is defined on PDF objects called transparency groups, note the word "groups".

Forgive me for being persistent, but is this difference in the context of the issue at hand not a technicality, because if I am not mistaken, a transparency group can simply consist of a single object, and if the transparency group is isolated, it can have its own color space? Again, I don't know how difficult it would be to code this into Scribus, so I don't want to pretend that this would be easy to code when in fact it is not, but from a purely conceptual standpoint, would it not be possible to put all CMYK objects in a layer with a blend mode into an isolated transparency group with a CMYK color space, and all RGB objects in that layer into another isolated transparency group with an RGB color space? Or instead of 2 color spaces per layer, there could be four color spaces, one for RGB solid colors, one for RGB images, etc.

As I said, I am just thinking about the concept, not about the practical difficulty of implementing this.

jghali

2025-08-27 21:39

administrator   ~0052973

>> because if I am not mistaken, a transparency group can simply consist of a single object, and if the transparency group is isolated, it can have its own color space

For objects to blend together, they have to be put in a same transparency group. So a transparency group with a single object is essentially useless. PDF ISO specifications from 2008 define transparency groups this way :

"A transparency group is a sequence of *consecutive objects* in a transparency stack that shall be collected together and composited to produce a single colour, shape, and opacity at each point. The result shall then be treated as if it were a single object for subsequent compositing operations."

>> would it not be possible to put all CMYK objects in a layer with a blend mode into an isolated transparency group with a CMYK color space, and all RGB objects in that layer into another isolated transparency group with an RGB color space?

No it's not, because of the consecutive objects requirement. For proper and consistent rendering vs screen, that would indeed require CMYK object and RGB objects to be also grouped together in the document stack, which would be an unrealistic requirement to put on users.

maximilian

2025-08-27 23:53

reporter   ~0052974

Ah yes, now I am beginning to see why this is more complicated than I initially thought, and also that I had not really grasped the concept of transparency groups in PDF.

Please tell me if my following observation is correct: Scribus does not have a feature that effectively represents what is represented in PDF by an isolated transparency group. As far as I (now think I) understand, isolating a transparency group in PDF basically means putting a white background between the group and its backdrop, and before the transparency group as a whole is blended against its backdrop, it is flattened down to the implicit white background. I am not aware of a feature in Scribus that represents this concept.

If this observation is correct, then the notion of a single common blending color space for all the elements in a Scribus document is inherent to the nature of a Scribus document, and introducing isolated transparency groups in a PDF file would not serve any purpose in representing the contents of the Scribus document.

However, I do not (yet) see any downside to letting the user choose whether this document-level blending color space should be an RGB space or a CMYK space. This would allow for both scenarios to be handled in a satisfactory manner. If the user uses CMYK colors and does not want these colors to be messed up by being blended in an RGB space, he can choose a CMYK color space, but if the user finds that the blending modes yield better results when being performed in an RGB space and does not care about the conversion issues you described (for example because the document already uses RGB colors), he can choose an RGB space as the document-wide blending color space.

I could think of two ways to implement this. The first one would be better in terms of user experience but probably more difficult to program. It's to make the common blending color space a property of the document itself. This way, the user could see the effects of the blend modes when performed in a CMYK color space directly in Scribus instead of only in the generated PDF file. But I suppose this would require considerable modifications to the way a document is rendered on screen.

The second way would be to make this an option in the PDF export dialog, at least for PDF/X-4 and for PDF 1.4 and above, and leave the on-screen rendering of the document as is (using an RGB blending color space). For inexperienced users, you could make the default option depend on the output intent and provide explanations in the tooltips, for example "RGB blending color space might mess up CMYK colors, but CMYK blending color space might look noticeably different from what was displayed in Scribus".

What do you think about this proposal?

maximilian

2025-08-28 23:03

reporter   ~0052982

OK, this is very interesting: When selecting the option in the PDF export dialog to use an RGB color profile for solid colors, the blending color space also seems to be set to that RGB profile. This makes sense and also solves the specific problem I was having, although I am not sure if this allows for enough flexibility in general. For example, someone might want to have both CMYK and RGB colors in the same document for some reason. But then, this would probably be a separate issue, albeit slightly related to this issue.

ale

2025-08-29 07:19

manager   ~0052983

Personally, I'm fine with the idea that one should choose a color space for the document.

@maximilian when all this is clear, would you mind to write a summary of your findings in the forum?
... some sort of short tutorial on how to blend with Scribus : - )

Issue History

Date Modified Username Field Change
2025-08-26 16:53 maximilian New Issue
2025-08-26 16:53 maximilian Tag Attached: color
2025-08-26 16:53 maximilian Tag Attached: colors
2025-08-26 16:53 maximilian Tag Attached: export to PDF
2025-08-26 16:53 maximilian Tag Attached: pdf export
2025-08-26 16:53 maximilian File Added: Color calculations.ods
2025-08-26 16:53 maximilian File Added: PDF Rendered by Acrobat Reader screenshot.png
2025-08-26 16:53 maximilian File Added: Sample document.pdf
2025-08-26 16:53 maximilian File Added: Sample document.sla
2025-08-27 17:46 maximilian Note Added: 0052961
2025-08-27 19:55 jghali Note Added: 0052962
2025-08-27 19:58 jghali Note Edited: 0052962
2025-08-27 20:03 maximilian Note Added: 0052963
2025-08-27 20:17 maximilian Note Added: 0052964
2025-08-27 20:21 jghali Note Added: 0052965
2025-08-27 20:23 maximilian Note Added: 0052966
2025-08-27 20:32 maximilian Note Added: 0052967
2025-08-27 20:39 maximilian Note Added: 0052968
2025-08-27 20:41 jghali Note Added: 0052969
2025-08-27 20:54 maximilian Note Added: 0052970
2025-08-27 20:54 jghali Note Added: 0052971
2025-08-27 21:17 maximilian Note Added: 0052972
2025-08-27 21:39 jghali Note Added: 0052973
2025-08-27 23:53 maximilian Note Added: 0052974
2025-08-28 23:03 maximilian Note Added: 0052982
2025-08-29 07:19 ale Note Added: 0052983