From 8475faa6482291d13e59573c93e9f35fb9a08ded Mon Sep 17 00:00:00 2001
From: celogeek <65178+celogeek@users.noreply.github.com>
Date: Sun, 1 Jan 2023 18:45:54 +0100
Subject: [PATCH] add brightness and contrast

---
 README.md                         |  6 ++--
 internal/epub/core.go             |  2 ++
 internal/epub/image_processing.go |  4 +--
 main.go                           | 54 ++++++++++++++++++++++---------
 4 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/README.md b/README.md
index a38f10b..e3b21be 100644
--- a/README.md
+++ b/README.md
@@ -76,10 +76,12 @@ The ePub include as a first page:
 # go-comic-converter -h
 
 Usage of go-comic-converter:
-  -algo string
-    	Algo for RGB to Grayscale: default, mean, luma, luster (default "default")
   -author string
     	Author of the epub (default "GO Comic Converter")
+  -brightness int
+    	Brightness readjustement: between -100 and 100, > 0 lighter, < 0 darker
+  -contrast int
+    	Contrast readjustement: between -100 and 100, > 0 more contrast, < 0 less contrast
   -input string
     	Source of comic to convert: directory, cbz, zip, cbr, rar, pdf
   -limitmb int
diff --git a/internal/epub/core.go b/internal/epub/core.go
index 6c3e392..1c6cef0 100644
--- a/internal/epub/core.go
+++ b/internal/epub/core.go
@@ -18,6 +18,8 @@ type ImageOptions struct {
 	Quality    int
 	Algo       string
 	Palette    color.Palette
+	Brightness int
+	Contrast   int
 }
 
 type EpubOptions struct {
diff --git a/internal/epub/image_processing.go b/internal/epub/image_processing.go
index bebbe23..01c36ae 100644
--- a/internal/epub/image_processing.go
+++ b/internal/epub/image_processing.go
@@ -139,9 +139,9 @@ func LoadImages(path string, options *ImageOptions) ([]*Image, error) {
 				// prepare filter
 				g := gift.New(
 					gift.Crop(findMarging(src)),
+					gift.Contrast(float32(options.Contrast)),
+					gift.Brightness(float32(options.Brightness)),
 					gift.ResizeToFit(options.ViewWidth, options.ViewHeight, gift.LanczosResampling),
-					// gift.Gamma(1.8),
-					// gift.Sigmoid(0.5, 5),
 				)
 				g.SetParallelization(false)
 
diff --git a/main.go b/main.go
index 6f025a1..315fd0b 100644
--- a/main.go
+++ b/main.go
@@ -56,14 +56,16 @@ func init() {
 }
 
 type Option struct {
-	Input   string
-	Output  string
-	Profile string
-	Author  string
-	Title   string
-	Quality int
-	NoCrop  bool
-	LimitMb int
+	Input      string
+	Output     string
+	Profile    string
+	Author     string
+	Title      string
+	Quality    int
+	NoCrop     bool
+	Brightness int
+	Contrast   int
+	LimitMb    int
 }
 
 func (o *Option) String() string {
@@ -84,14 +86,16 @@ func (o *Option) String() string {
 	return fmt.Sprintf(`Go Comic Converter
 
 Options:
-    Input   : %s
-    Output  : %s
-    Profile : %s - %s - %dx%d - %d levels of gray
-    Author  : %s
-    Title   : %s
-    Quality : %d
-    Crop    : %v
-    LimitMb : %s
+    Input     : %s
+    Output    : %s
+    Profile   : %s - %s - %dx%d - %d levels of gray
+    Author    : %s
+    Title     : %s
+    Quality   : %d
+    Crop      : %v
+    Brightness: %d
+    Contrast  : %d
+    LimitMb   : %s
 `,
 		o.Input,
 		o.Output,
@@ -100,6 +104,8 @@ Options:
 		o.Title,
 		o.Quality,
 		!o.NoCrop,
+		o.Brightness,
+		o.Contrast,
 		limitmb,
 	)
 }
@@ -124,6 +130,8 @@ func main() {
 	flag.StringVar(&opt.Title, "title", "", "Title of the epub")
 	flag.IntVar(&opt.Quality, "quality", 85, "Quality of the image")
 	flag.BoolVar(&opt.NoCrop, "nocrop", false, "Disable cropping")
+	flag.IntVar(&opt.Brightness, "brightness", 0, "Brightness readjustement: between -100 and 100, > 0 lighter, < 0 darker")
+	flag.IntVar(&opt.Contrast, "contrast", 0, "Contrast readjustement: between -100 and 100, > 0 more contrast, < 0 less contrast")
 	flag.IntVar(&opt.LimitMb, "limitmb", 0, "Limit size of the ePub: Default nolimit (0), Minimum 20")
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr, "Usage of %s:\n", filepath.Base(os.Args[0]))
@@ -188,6 +196,18 @@ func main() {
 		os.Exit(1)
 	}
 
+	if opt.Brightness < -100 || opt.Brightness > 100 {
+		fmt.Fprintln(os.Stderr, "Brightness should be between -100 and 100")
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	if opt.Contrast < -100 || opt.Contrast > 100 {
+		fmt.Fprintln(os.Stderr, "Contrast should be between -100 and 100")
+		flag.Usage()
+		os.Exit(1)
+	}
+
 	if opt.Title == "" {
 		ext := filepath.Ext(defaultOutput)
 		opt.Title = filepath.Base(defaultOutput[0 : len(defaultOutput)-len(ext)])
@@ -207,6 +227,8 @@ func main() {
 			Quality:    opt.Quality,
 			Crop:       !opt.NoCrop,
 			Palette:    profile.Palette,
+			Brightness: opt.Brightness,
+			Contrast:   opt.Contrast,
 		},
 	}).Write(); err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)