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extgstate.go
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extgstate.go
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// seehuhn.de/go/pdf - a library for reading and writing PDF files
// Copyright (C) 2024 Jochen Voss <voss@seehuhn.de>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package reader
import (
"seehuhn.de/go/pdf"
"seehuhn.de/go/pdf/graphics"
)
// ReadExtGState reads an graphics state parameter dictionary from a PDF file.
func (r *Reader) ReadExtGState(ref pdf.Object, defaultName pdf.Name) (*graphics.ExtGState, error) {
dict, err := pdf.GetDictTyped(r.R, ref, "ExtGState")
if err != nil {
return nil, err
}
param := &graphics.Parameters{}
var set graphics.StateBits
var overprintFillSet bool
var bg1, bg2 pdf.Object
var ucr1, ucr2 pdf.Object
var tr1, tr2 pdf.Object
for key, v := range dict {
switch key {
case "Font":
a, err := pdf.GetArray(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
if len(a) != 2 {
break
}
size, err := pdf.GetNumber(r.R, a[1])
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
F, err := r.ReadFont(a[0], "")
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.TextFont = F
param.TextFontSize = float64(size)
set |= graphics.StateTextFont
case "TK":
val, err := pdf.GetBoolean(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.TextKnockout = bool(val)
set |= graphics.StateTextKnockout
case "LW":
lw, err := pdf.GetNumber(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.LineWidth = float64(lw)
set |= graphics.StateLineWidth
case "LC":
lc, err := pdf.GetInteger(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.LineCap = graphics.LineCapStyle(lc)
set |= graphics.StateLineCap
case "LJ":
lj, err := pdf.GetInteger(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.LineJoin = graphics.LineJoinStyle(lj)
set |= graphics.StateLineJoin
case "ML":
ml, err := pdf.GetNumber(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.MiterLimit = float64(ml)
set |= graphics.StateMiterLimit
case "D":
dashPattern, phase, err := readDash(r.R, v)
if err != nil {
return nil, err
} else if dashPattern != nil {
param.DashPattern = dashPattern
param.DashPhase = phase
set |= graphics.StateLineDash
}
case "RI":
ri, err := pdf.GetName(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.RenderingIntent = graphics.RenderingIntent(ri)
set |= graphics.StateRenderingIntent
case "SA":
val, err := pdf.GetBoolean(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.StrokeAdjustment = bool(val)
set |= graphics.StateStrokeAdjustment
case "BM":
param.BlendMode = v
set |= graphics.StateBlendMode
case "SMask":
param.SoftMask = v
set |= graphics.StateSoftMask
case "CA":
ca, err := pdf.GetNumber(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.StrokeAlpha = float64(ca)
set |= graphics.StateStrokeAlpha
case "ca":
ca, err := pdf.GetNumber(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.FillAlpha = float64(ca)
set |= graphics.StateFillAlpha
case "AIS":
ais, err := pdf.GetBoolean(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.AlphaSourceFlag = bool(ais)
set |= graphics.StateAlphaSourceFlag
case "UseBlackPtComp":
val, err := pdf.GetName(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.BlackPointCompensation = val
set |= graphics.StateBlackPointCompensation
case "OP":
op, err := pdf.GetBoolean(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.OverprintStroke = bool(op)
set |= graphics.StateOverprint
case "op":
op, err := pdf.GetBoolean(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.OverprintFill = bool(op)
set |= graphics.StateOverprint
overprintFillSet = true
case "OPM":
opm, err := pdf.GetInteger(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
if opm != 0 {
param.OverprintMode = 1
}
set |= graphics.StateOverprintMode
case "BG":
bg1 = v
case "BG2":
bg2 = v
case "UCR":
ucr1 = v
case "UCR2":
ucr2 = v
case "TR":
tr1 = v
case "TR2":
tr2 = v
case "HT":
param.Halftone = v
set |= graphics.StateHalftone
case "HTO":
a, err := pdf.GetArray(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
if len(a) != 2 {
break
}
x, err := pdf.GetNumber(r.R, a[0])
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
y, err := pdf.GetNumber(r.R, a[1])
if pdf.IsMalformed(err) {
break
}
param.HalftoneOriginX = float64(x)
param.HalftoneOriginY = float64(y)
set |= graphics.StateHalftoneOrigin
case "FL":
fl, err := pdf.GetNumber(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.FlatnessTolerance = float64(fl)
set |= graphics.StateFlatnessTolerance
case "SM":
sm, err := pdf.GetNumber(r.R, v)
if pdf.IsMalformed(err) {
break
} else if err != nil {
return nil, err
}
param.SmoothnessTolerance = float64(sm)
set |= graphics.StateSmoothnessTolerance
}
}
if set&graphics.StateOverprint != 0 && !overprintFillSet {
param.OverprintFill = param.OverprintStroke
}
if bg2 != nil {
param.BlackGeneration = bg2
set |= graphics.StateBlackGeneration
} else if bg1 != nil {
param.BlackGeneration = bg1
set |= graphics.StateBlackGeneration
}
if ucr2 != nil {
param.UndercolorRemoval = ucr2
set |= graphics.StateUndercolorRemoval
} else if ucr1 != nil {
param.UndercolorRemoval = ucr1
set |= graphics.StateUndercolorRemoval
}
if tr2 != nil {
param.TransferFunction = tr2
set |= graphics.StateTransferFunction
} else if tr1 != nil {
param.TransferFunction = tr1
set |= graphics.StateTransferFunction
}
res := &graphics.ExtGState{
Res: pdf.Res{
DefName: defaultName,
Data: ref,
},
Value: graphics.State{
Parameters: param,
Set: set,
},
}
return res, nil
}
func readDash(r pdf.Getter, obj pdf.Object) (pat []float64, ph float64, err error) {
defer func() {
if _, isMalformed := err.(*pdf.MalformedFileError); isMalformed {
err = nil
}
}()
a, err := pdf.GetArray(r, obj)
if len(a) != 2 { // either error or malformed
return nil, 0, err
}
dashPattern, err := pdf.GetArray(r, a[0])
if err != nil {
return nil, 0, err
}
phase, err := pdf.GetNumber(r, a[1])
if err != nil {
return nil, 0, err
}
pat = make([]float64, len(dashPattern))
for i, obj := range dashPattern {
x, err := pdf.GetNumber(r, obj)
if err != nil {
return nil, 0, err
}
pat[i] = float64(x)
}
return pat, float64(phase), nil
}