[minor] Rearranging thumbnails handling:

* Added KFX reader
* Restructure MOBI reader so both KFX and MOBI readers have similar behavior.
* Removing "stretch" configuration for MOBI thumbnails - always false.

Author: rupor-github

README.md

@@ -217,5 +217,4 @@ incorporate your changes.
 
 ### TODO
 
-- Add thumbnail support for KFX files
 - Expand history reports with some useful statistics

config/config.yaml.tmpl

@@ -22,9 +22,6 @@ thumbnails:
   #---- when thumbnail is prepared it will be scaled to following dimensions
   width: 330
   height: 470
-  #---- when true - instead of using prepared thumbnail from book, its cover image (if available) will be
-  #---- scaled to requested dimensions
-  stretch: false
 
 logging:
   #---- controls terminal (stdout, stderr) output

go.mod

@@ -1,8 +1,9 @@
 module sync2kindle
 
-go 1.23.5
+go 1.23
 
 require (
+	github.com/amazon-ion/ion-go v1.5.0
 	github.com/disintegration/imaging v1.6.2
 	github.com/dustin/go-humanize v1.0.1
 	github.com/go-ole/go-ole v1.3.0

go.sum

@@ -1,7 +1,10 @@
 github.com/BurntSushi/toml v1.4.1-0.20240526193622-a339e1f7089c h1:pxW6RcqyfI9/kWtOwnv/G+AzdKuy2ZrqINhenH4HyNs=
 github.com/BurntSushi/toml v1.4.1-0.20240526193622-a339e1f7089c/go.mod h1:ukJfTF/6rtPPRCnwkur4qwRxa8vTRFBF0uk2lLoLwho=
+github.com/amazon-ion/ion-go v1.5.0 h1:fxsAyFda8N9HsM2xYbQSxJ3Qi/oLn0xzLoiXWG3bseg=
+github.com/amazon-ion/ion-go v1.5.0/go.mod h1:3ZEje8i20TiIPVZlN+KE3B2ppZ1B8d9F/KaT7Dtec+k=
 github.com/cpuguy83/go-md2man/v2 v2.0.5 h1:ZtcqGrnekaHpVLArFSe4HK5DoKx1T0rq2DwVB0alcyc=
 github.com/cpuguy83/go-md2man/v2 v2.0.5/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/disintegration/imaging v1.6.2 h1:w1LecBlG2Lnp8B3jk5zSuNqd7b4DXhcjwek1ei82L+c=
@@ -22,6 +25,7 @@ github.com/go-playground/validator/v10 v10.21.0 h1:4fZA11ovvtkdgaeev9RGWPgc1uj3H
 github.com/go-playground/validator/v10 v10.21.0/go.mod h1:dbuPbCMFw/DrkbEynArYaCwl3amGuJotoKCe95atGMM=
 github.com/go-task/slim-sprig/v3 v3.0.0 h1:sUs3vkvUymDpBKi3qH1YSqBQk9+9D/8M2mN1vB6EwHI=
 github.com/go-task/slim-sprig/v3 v3.0.0/go.mod h1:W848ghGpv3Qj3dhTPRyJypKRiqCdHZiAzKg9hl15HA8=
+github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
@@ -40,6 +44,8 @@ github.com/rupor-github/gencfg v1.0.2 h1:LJnOoOL7ob9PBjikL4eHEhVruAhl6zCOFvFheuE
 github.com/rupor-github/gencfg v1.0.2/go.mod h1:41OMdMXM3iYYcjxrPwh3WYkud3+0Pf+RM3P2FovXG80=
 github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/urfave/cli/v2 v2.27.5 h1:WoHEJLdsXr6dDWoJgMq/CboDmyY/8HMMH1fTECbih+w=
@@ -76,8 +82,11 @@ golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
 golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
 golang.org/x/tools v0.21.1-0.20240531212143-b6235391adb3 h1:SHq4Rl+B7WvyM4XODon1LXtP7gcG49+7Jubt1gWWswY=
 golang.org/x/tools v0.21.1-0.20240531212143-b6235391adb3/go.mod h1:bqv7PJ/TtlrzgJKhOAGdDUkUltQapRik/UEHubLVBWo=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.5.1 h1:4bH5o3b5ZULQ4UrBmP+63W9r7qIkqJClEA9ko5YKx+I=

thumbs/config.go

@@ -1,9 +1,8 @@
 package thumbs
 
 type ThumbnailsConfig struct {
-	Width   int  `yaml:"width" validate:"required,gt=0"`
-	Height  int  `yaml:"height" validate:"required,gt=0"`
-	Stretch bool `yaml:"stretch"`
+	Width  int `yaml:"width" validate:"required,gt=0"`
+	Height int `yaml:"height" validate:"required,gt=0"`
 
 	Dir string `yaml:"-"` // internal use only
 }

thumbs/imgutils/jfif.go

@@ -0,0 +1,48 @@
+package imgutils
+
+import (
+	"bytes"
+	"encoding/binary"
+)
+
+// This is specific to go - when encoding jpeg standard encoder does not create JFIF APP0 segment and Kindle does not like it.
+
+// JpegDPIType specifyes type of the DPI units
+type JpegDPIType uint8
+
+// DPI units type values
+const (
+	DpiNoUnits JpegDPIType = iota
+	DpiPxPerInch
+	DpiPxPerSm
+)
+
+var (
+	marker = []byte{0xFF, 0xE0}                               // APP0 segment marker
+	jfif   = []byte{0x4A, 0x46, 0x49, 0x46, 0x00, 0x01, 0x02} // jfif + version
+)
+
+// SetJpegDPI creates JFIF APP0 with provided DPI if segment is missing in image.
+func SetJpegDPI(buf *bytes.Buffer, dpit JpegDPIType, xdensity, ydensity int16) (*bytes.Buffer, bool) {
+
+	data := buf.Bytes()
+
+	// If JFIF APP0 segment is there - do not do anything
+	if bytes.Equal(data[2:4], marker) {
+		return buf, false
+	}
+
+	var newbuf = new(bytes.Buffer)
+
+	newbuf.Write(data[:2])
+	newbuf.Write(marker)
+	binary.Write(newbuf, binary.BigEndian, uint16(0x10)) // length
+	newbuf.Write(jfif)
+	binary.Write(newbuf, binary.BigEndian, uint8(dpit))
+	binary.Write(newbuf, binary.BigEndian, uint16(xdensity))
+	binary.Write(newbuf, binary.BigEndian, uint16(ydensity))
+	binary.Write(newbuf, binary.BigEndian, uint16(0)) // no thumbnail segment
+	newbuf.Write(data[2:])
+
+	return newbuf, true
+}

thumbs/kfx/ion.go

@@ -0,0 +1,57 @@
+package kfx
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/amazon-ion/ion-go/ion"
+)
+
+const (
+	largestKnownSymbol = 834
+	//
+	symBookMetadata        = 490
+	symCategorizedMetadata = 491
+	symExternalResource    = 164
+	symThumbnails          = 214
+	symRawMedia            = 417
+)
+
+var (
+	ionBVM            = []byte{0xE0, 1, 0, 0xEA} // binary version marker
+	sharedSymbolTable = createSST(largestKnownSymbol)
+)
+
+// Actual names for symbols could be obtained by looking at EpubToKFXConverter-4.0.jar from Kindle Previewer 3
+// with enum of interest in class file "com.amazon.kaf.c/B.class" presently.
+func createSST(maxID uint64) ion.SharedSymbolTable {
+	symbols := make([]string, 0, maxID)
+	for i := len(ion.V1SystemSymbolTable.Symbols()) + 1; i <= len(ion.V1SystemSymbolTable.Symbols())+int(maxID); i++ {
+		symbols = append(symbols, fmt.Sprintf("$%d", i))
+	}
+	return ion.NewSharedSymbolTable("YJ_symbols", 10, symbols)
+}
+
+func createProlog() []byte {
+	buf := bytes.Buffer{}
+	if err := ion.NewBinaryWriter(&buf, sharedSymbolTable).Finish(); err != nil {
+		panic(err)
+	}
+	return buf.Bytes()
+}
+
+func decodeData(prolog, data []byte, v any) error {
+	if err := ion.Unmarshal(append(prolog, data[len(ionBVM):]...), v, sharedSymbolTable); err != nil {
+		return err
+	}
+	return nil
+}
+
+func decodeST(data []byte) (ion.SymbolTable, error) {
+	r := ion.NewReaderCat(bytes.NewReader(data), ion.NewCatalog(sharedSymbolTable))
+	r.Next() // we are not interested in the actual values and in most cases this will return false anyways
+	if err := r.Err(); err != nil {
+		return nil, err
+	}
+	return r.SymbolTable(), nil
+}