Page.CMYKProfile; cera -cmyk writes a CMYK TIFF

cmd/cera/commands_test.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"encoding/binary"
 	"encoding/json"
 	"fmt"
 	"os"
@@ -249,7 +250,7 @@ func TestFormats(t *testing.T) {
 	for ext, magic := range map[string]string{"jpg": "\xff\xd8\xff", "tif": "II*\x00", "webp": "RIFF", "png": "\x89PNG"} {
 		for _, gray := range []bool{false, true} {
 			out := filepath.Join(dir, "p-%d."+ext)
-			if err := run(in, cera.OpenOptions{}, 72, 2, out, false, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 80, gray); err != nil {
+			if err := run(in, cera.OpenOptions{}, 72, 2, out, false, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 80, gray, false); err != nil {
 				t.Fatalf("%s, grey %v: %v", ext, gray, err)
 			}
 			b, err := os.ReadFile(fmt.Sprintf(out, 2))
@@ -258,10 +259,55 @@ func TestFormats(t *testing.T) {
 			}
 		}
 	}
-	if err := run(in, cera.OpenOptions{}, 72, 1, filepath.Join(dir, "p.jpg"), true, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 0, false); err == nil {
+	if err := run(in, cera.OpenOptions{}, 72, 1, filepath.Join(dir, "p.jpg"), true, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 0, false, false); err == nil {
 		t.Error("a transparent JPEG was written")
 	}
-	if err := run(in, cera.OpenOptions{}, 72, 1, filepath.Join(dir, "p.bmp"), false, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 0, false); err == nil {
+	if err := run(in, cera.OpenOptions{}, 72, 1, filepath.Join(dir, "p.bmp"), false, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 0, false, false); err == nil {
 		t.Error("a format nobody writes was written")
 	}
 }
+
+// -cmyk writes the inks into a TIFF with the profile they are for.
+func TestCMYKTIFF(t *testing.T) {
+	dir := t.TempDir()
+	in := textPDF(t, dir, "in.pdf")
+	icc, err := os.ReadFile(filepath.Join("..", "..", "internal", "cmyk", "testdata", "toy-lut16.icc"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	out := filepath.Join(dir, "p.tif")
+	if err := run(in, cera.OpenOptions{CMYKProfile: icc}, 72, 1, out, false, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 0, false, true); err != nil {
+		t.Fatal(err)
+	}
+	b, err := os.ReadFile(out)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// The IFD: PhotometricInterpretation 5 (separated), InkSet 1 (CMYK)
+	// and the profile (34675).
+	le := binary.LittleEndian
+	ifd := int(le.Uint32(b[4:]))
+	tags := map[uint16][]byte{}
+	for i := range int(le.Uint16(b[ifd:])) {
+		e := b[ifd+2+12*i:][:12]
+		tags[le.Uint16(e)] = e
+	}
+	if e := tags[262]; e == nil || le.Uint16(e[8:]) != 5 {
+		t.Error("not separated")
+	}
+	if e := tags[332]; e == nil || le.Uint16(e[8:]) != 1 {
+		t.Error("no CMYK ink set")
+	}
+	if e := tags[34675]; e == nil || !bytes.Equal(b[le.Uint32(e[8:]):][:le.Uint32(e[4:])], icc) {
+		t.Error("profile not embedded")
+	}
+	for _, c := range []struct {
+		out         string
+		transparent bool
+		gray        bool
+	}{{"p.png", false, false}, {"p.tif", true, false}, {"p.tif", false, true}} {
+		if err := run(in, cera.OpenOptions{}, 72, 1, filepath.Join(dir, c.out), c.transparent, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, "encode", 0, c.gray, true); err == nil {
+			t.Errorf("-cmyk %+v was written", c)
+		}
+	}
+}

cmd/cera/go.mod

@@ -3,7 +3,7 @@ module github.com/timzifer/cera/cmd/cera
 go 1.27.1
 
 require (
-	github.com/timzifer/calamus v0.2.0
+	github.com/timzifer/calamus v0.3.1-0.20261014111300-bd50c1615f30
 	github.com/timzifer/cera v0.0.0
 )
 

cmd/cera/go.sum

@@ -10,8 +10,8 @@ github.com/go-opentype/opentype v0.15.0 h1:ioE3eCbNZavlk/w073J3uX5FKjqhgOHQw+wZZ
 github.com/go-opentype/opentype v0.15.0/go.mod h1:ZB31jTJl2mhPESXYMuUW+p36UrOabw/2+6mtyh/vNnI=
 github.com/tannevaled/gobig2 v0.2.0 h1:yx97/ltljALrIWDFVqHjPUIjAp3bfUUhH8Z8UROvNLc=
 github.com/tannevaled/gobig2 v0.2.0/go.mod h1:X0S1H+N35kg6zYgVYRqGMsGj3C35zs+iA2r1MXyPcV4=
-github.com/timzifer/calamus v0.2.0 h1:pOdCAVu75XASMhL5fiI3+qObJMCtiKZ1ehA4ZOOPWdA=
-github.com/timzifer/calamus v0.2.0/go.mod h1:Z6fVRZRraaG0hgfvqynq9TM9vCq1ZGVm8AgDvnugCqw=
+github.com/timzifer/calamus v0.3.1-0.20261014111300-bd50c1615f30 h1:vivSe451Wk0AyCPzVB2XcsPxK1lrLkForE477KaP/RE=
+github.com/timzifer/calamus v0.3.1-0.20261014111300-bd50c1615f30/go.mod h1:Z6fVRZRraaG0hgfvqynq9TM9vCq1ZGVm8AgDvnugCqw=
 github.com/timzifer/go-highway v0.0.13-timzifer.1 h1:+DREnc494whho5HlwAkjX1m09fxDLdG3n0hYRBm6AFY=
 github.com/timzifer/go-highway v0.0.13-timzifer.1/go.mod h1:ZXPijqyP0TXlwJXJClrFCdp4q+zlQNAMZ3ncCROV648=
 github.com/timzifer/stilus v0.11.0 h1:vCj79ga4NRr7oE/6YYxnly3UMJleTj9tNyPYmRVY/bE=

cmd/cera/main.go

@@ -5,6 +5,7 @@
 //	cera -dpi 150 -o 'out-%d.png' input.pdf   # all pages
 //	cera -o 'out-%d.jpg' -quality 85 input.pdf   # or .tif, .webp
 //	cera -gray -o 'fax-%d.tif' input.pdf
+//	cera -cmyk -o 'press-%d.tif' print.pdf   # the inks, with the profile
 //	cera -field name=Ada -field agree=Yes -page 1 form.pdf
 //	cera -cmyk-profile CoatedFOGRA39.icc -page 1 print.pdf
 //
@@ -62,6 +63,7 @@ func main() {
 	out := flag.String("o", "page-%d.png", "output file; %d is replaced by the page number, and its ending says what is written: .png, .jpg, .tif or .webp")
 	quality := flag.Int("quality", 0, "quality of a JPEG, 1 to 100 (default 75)")
 	gray := flag.Bool("gray", false, "draw in grey")
+	cmykOut := flag.Bool("cmyk", false, "draw in the CMYK of the document, as a press gets it, into a .tif that carries the profile of the output intent or of -cmyk-profile")
 	password := flag.String("password", "", "password of an encrypted file")
 	transparent := flag.Bool("transparent", false, "leave the background transparent")
 	timeout := flag.Duration("timeout", time.Minute, "deadline per page")
@@ -123,14 +125,24 @@ func main() {
 		}
 		opt.CMYKProfile = b
 	}
-	if err := run(flag.Arg(0), opt, *dpi, *page, *out, *transparent, *timeout, *verbose, *workers, mode, box, filter, fields, *pngMode, *quality, *gray); err != nil {
+	if err := run(flag.Arg(0), opt, *dpi, *page, *out, *transparent, *timeout, *verbose, *workers, mode, box, filter, fields, *pngMode, *quality, *gray, *cmykOut); err != nil {
 		fmt.Fprintln(os.Stderr, "cera:", err)
 		os.Exit(1)
 	}
 }
 
-func run(in string, opt cera.OpenOptions, dpi float64, page int, out string, transparent bool, timeout time.Duration, verbose bool, workers int, annots cera.AnnotMode, box cera.PageBox, filter cera.ImageFilter, fields []string, pngMode string, quality int, gray bool) error {
+func run(in string, opt cera.OpenOptions, dpi float64, page int, out string, transparent bool, timeout time.Duration, verbose bool, workers int, annots cera.AnnotMode, box cera.PageBox, filter cera.ImageFilter, fields []string, pngMode string, quality int, gray, cmykOut bool) error {
 	format := strings.ToLower(filepath.Ext(out))
+	if cmykOut {
+		switch {
+		case gray:
+			return fmt.Errorf("-cmyk and -gray: draw in one or the other")
+		case transparent:
+			return fmt.Errorf("-cmyk: what is drawn on nothing is paper, no ink; -transparent has no say")
+		case format != ".tif" && format != ".tiff":
+			return fmt.Errorf("-o %q: -cmyk writes a TIFF, want a name that ends in .tif", out)
+		}
+	}
 	switch format {
 	case ".png", ".tif", ".tiff", ".webp":
 	case ".jpg", ".jpeg":
@@ -184,14 +196,20 @@ func run(in string, opt cera.OpenOptions, dpi float64, page int, out string, tra
 		}
 		var img image.Image
 		var sw *streamPNG
+		var icc []byte
 		t0 := time.Now()
-		if gray {
+		switch {
+		case cmykOut:
+			dst := image.NewCMYK(p.Bounds(dpi / 72))
+			img, icc = dst, p.CMYKProfile()
+			err = p.RenderCMYK(context.Background(), dst, ropt)
+		case gray:
 			// In grey the page is drawn a band at a time, without the
 			// page in colour.
 			dst := image.NewGray(p.Bounds(dpi / 72))
 			img = dst
 			err = p.RenderGray(context.Background(), dst, ropt)
-		} else {
+		default:
 			dst := image.NewRGBA(p.Bounds(dpi / 72))
 			img = dst
 			if pngMode == "stream" && format == ".png" {
@@ -222,7 +240,7 @@ func run(in string, opt cera.OpenOptions, dpi float64, page int, out string, tra
 		case format == ".png":
 			err = writePNG(name, img, pngMode)
 		default:
-			err = writeImage(name, img, format, quality)
+			err = writeImage(name, img, format, quality, icc)
 		}
 		if err != nil {
 			return err
@@ -276,8 +294,9 @@ func writePNG(name string, img image.Image, mode string) error {
 
 // writeImage writes img to the file name in one of the other formats
 // calamus encodes: a JPEG at quality, a TIFF with LZW, a WebP without
-// loss. A TIFF is one page; several pages are several files.
-func writeImage(name string, img image.Image, format string, quality int) error {
+// loss. A TIFF is one page; several pages are several files. A TIFF
+// carries icc, the profile of its samples, unless that is nil.
+func writeImage(name string, img image.Image, format string, quality int, icc []byte) error {
 	f, err := os.Create(name)
 	if err != nil {
 		return err
@@ -286,7 +305,7 @@ func writeImage(name string, img image.Image, format string, quality int) error
 	case ".jpg", ".jpeg":
 		err = (&jpeg.Encoder{Quality: quality}).Encode(f, img)
 	case ".tif", ".tiff":
-		err = tiff.Encode(f, img, &tiff.Options{Compression: tiff.LZW, Predictor: true})
+		err = tiff.Encode(f, img, &tiff.Options{Compression: tiff.LZW, Predictor: true, ICCProfile: icc})
 	case ".webp":
 		err = webp.Encode(f, img)
 	}

cmd/cera/main_test.go

@@ -46,7 +46,7 @@ func TestPNGModes(t *testing.T) {
 		for _, mode := range []string{"stdlib", "encode", "stream"} {
 			name := fmt.Sprintf("%s, transparent %v, %s", tc.file, tc.transparent, mode)
 			out := filepath.Join(t.TempDir(), "p-%d.png")
-			if err := run(in, cera.OpenOptions{}, 150, tc.page, out, tc.transparent, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, mode, 0, false); err != nil {
+			if err := run(in, cera.OpenOptions{}, 150, tc.page, out, tc.transparent, time.Minute, false, 0, cera.AnnotsView, cera.BoxCrop, cera.ImageNearest, nil, mode, 0, false, false); err != nil {
 				t.Fatalf("%s: %v", name, err)
 			}
 			got := decode(t, fmt.Sprintf(out, tc.page))

cmykout.go

@@ -198,6 +198,20 @@ func (d *Document) rgbInks(r, g, b float64) [4]float64 {
 	return [4]float64{c - k, m - k, y - k, k}
 }
 
+// CMYKProfile returns the ICC profile of the CMYK RenderCMYK draws p in,
+// for what is written of it to say so (a TIFF, say): the caller's
+// (OpenOptions.CMYKProfile), or that of the output intent of the page or
+// of the document. It is nil where that is the bundled SWOP profile, with
+// NaiveCMYK, and where cera cannot use the intent's profile. The bytes are
+// the caller's or decoded anew; they are not to be changed.
+func (p *Page) CMYKProfile() []byte {
+	cs, _ := p.cmykDoc().deviceCMYK()
+	if cs == nil || cs.icc == nil {
+		return nil
+	}
+	return cs.icc()
+}
+
 // cmykPixels is how many pixels of a page RenderCMYK draws at a time: 4 MB
 // of RGBA.
 const cmykPixels = 1 << 20

cmykout_test.go

@@ -1,6 +1,7 @@
 package cera
 
 import (
+	"bytes"
 	"context"
 	"image"
 	"os"
@@ -187,3 +188,40 @@ func TestRenderCMYKRegion(t *testing.T) {
 		t.Errorf("bands %v of region %v", bands, region)
 	}
 }
+
+// TestPageCMYKProfile returns the profile RenderCMYK draws a page in: the
+// caller's, the page's output intent's over the document's, none for the
+// bundled one.
+func TestPageCMYKProfile(t *testing.T) {
+	toy, swop := readToyProfile(t), swopProfileFile(t)
+	bad := bytes.Clone(toy)
+	copy(bad[132+12+4:], []byte{0xff, 0xff, 0xff, 0xff}) // A2B0 out of range
+	copy(bad[132+24+4:], []byte{0xff, 0xff, 0xff, 0xff}) // A2B1 too
+	pages := pageIntentPDF(intent("GTS_PDFX", 101), [3]string{intent("GTS_PDFX", 100), "", intent("GTS_PDFX", 102)}, toy, swop, bad)
+	for _, tt := range []struct {
+		name string
+		data []byte
+		opt  OpenOptions
+		want [3][]byte
+	}{
+		{"intents", pages, OpenOptions{}, [3][]byte{toy, swop, swop}},
+		{"caller's", pages, OpenOptions{CMYKProfile: toy}, [3][]byte{toy, toy, toy}},
+		{"naive", pages, OpenOptions{NaiveCMYK: true}, [3][]byte{}},
+		{"ignored", pages, OpenOptions{IgnoreOutputIntent: true}, [3][]byte{}},
+		{"bundled", pageIntentPDF("", [3]string{}), OpenOptions{}, [3][]byte{}},
+	} {
+		doc, err := OpenWith(tt.data, tt.opt)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for i, want := range tt.want {
+			p, err := doc.Page(i)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got := p.CMYKProfile(); !bytes.Equal(got, want) || (got == nil) != (want == nil) {
+				t.Errorf("%s, page %d: %d bytes, want %d", tt.name, i, len(got), len(want))
+			}
+		}
+	}
+}

color.go

@@ -38,8 +38,9 @@ type colorSpace struct {
 	// colorants are the names of the colorants of a tint space.
 	colorants []string
 	// cmyk is the profile a CMYK space converts through, nil for the naive
-	// conversion.
+	// conversion; icc returns its bytes, nil for the bundled one.
 	cmyk *cmyk.Table
+	icc  func() []byte
 
 	once sync.Once
 	tint *[256][3]uint8 // one-component tint transform, tabulated
@@ -429,7 +430,7 @@ func (d *Document) profileCMYK(ref pdf.Ref, data func() []byte) (*colorSpace, st
 	}
 	e := csEntry{nil, "icc-lut"}
 	if t, err := cmyk.Load(data()); err == nil {
-		e = csEntry{&colorSpace{kind: csCMYK, n: 4, cmyk: t}, ""}
+		e = csEntry{&colorSpace{kind: csCMYK, n: 4, cmyk: t, icc: data}, ""}
 	}
 	d.csMu.Lock()
 	defer d.csMu.Unlock()
@@ -520,7 +521,8 @@ func (d *Document) intentCMYK(list pdf.Object) (cs *colorSpace, approx string, o
 			continue
 		}
 		ref, _ := prof.Ref()
-		cs, approx = d.profileCMYK(ref, func() []byte { return data })
+		// Decoded again when asked for (Page.CMYKProfile), not kept.
+		cs, approx = d.profileCMYK(ref, func() []byte { return d.r.Decode(s).Data })
 		return cs, approx, true
 	}
 	return nil, "", false

docs/features.md

@@ -202,7 +202,8 @@ displayed page:
   and spot colours through their alternate, RGB through the profile's
   colour-to-ink table (B2A) or as PDF converts DeviceRGB; blend modes on
   the inks' complements, black kept or taken in the non-separable ones
-  (#209)
+  (#209); `Page.CMYKProfile` is the ICC profile they are for, and
+  `cera -cmyk` writes them as a CMYK TIFF with it
 
 ### Metadata
 

docs/usage.md

@@ -38,8 +38,9 @@ colorants named Cyan, Magenta, Yellow and Black on those inks, and RGB is
 converted through the profile's colour-to-ink table where it has one, else
 as PDF converts DeviceRGB. What is drawn on nothing is paper, no ink. The
 page is drawn twice, about twice the time of `Render`; overprint is not
-simulated in it yet (#155). A page in another RGB than sRGB is not there
-yet.
+simulated in it yet (#155). `page.CMYKProfile()` is the ICC profile the
+inks are for, to embed in what is written of them (nil for the bundled
+SWOP). A page in another RGB than sRGB is not there yet.
 
 A viewer that turns its view asks for the page turned:
 `page.Rotated(90)` is the page as it is shown then — a `Page` with its
@@ -1037,8 +1038,10 @@ it does not draw with: it writes the PNGs with
 [calamus](https://github.com/timzifer/calamus), which encodes them in bands
 on all cores (encoding was most of the command's time with `image/png`).
 The ending of `-o` says what is written: `.png`, `.jpg` (`-quality`),
-`.tif` (LZW) or `.webp` (without loss); `-gray` draws in grey. A TIFF is
-one page: several pages are several files.
+`.tif` (LZW) or `.webp` (without loss); `-gray` draws in grey, `-cmyk`
+in the CMYK of the document into a TIFF of inks that carries the profile
+of the output intent or of `-cmyk-profile`. A TIFF is one page: several
+pages are several files.
 
 Besides drawing, the command does what the library does, as subcommands
 (`cera <command> -h` lists the flags of each):

document.go

@@ -158,7 +158,7 @@ func open(read func(pdf.Options) (*pdf.Document, error), opt OpenOptions) (doc *
 		if err != nil {
 			return nil, fmt.Errorf("cera: CMYKProfile: %w", err)
 		}
-		devCMYK = &colorSpace{kind: csCMYK, n: 4, cmyk: t}
+		devCMYK = &colorSpace{kind: csCMYK, n: 4, cmyk: t, icc: func() []byte { return opt.CMYKProfile }}
 	}
 	if opt.NaiveCMYK {
 		devCMYK = spaceCMYKNaive