From 76894654c7c3f6888b797ff02d2fe5742d1751d4 Mon Sep 17 00:00:00 2001
From: Mereng <vladislav-sedov@yandex.ru>
Date: Thu, 17 Jun 2021 18:57:39 +0200
Subject: [PATCH] Support brightness and contrast

---
 options.go |  2 ++
 resizer.go | 34 ++++++++++++++++++++++++++++++++++
 vips.go    | 22 ++++++++++++++++++++++
 vips.h     | 10 ++++++++++
 4 files changed, 68 insertions(+)

diff --git a/options.go b/options.go
index 3d46fb2..307f868 100644
--- a/options.go
+++ b/options.go
@@ -223,6 +223,8 @@ type Options struct {
 	Sharpen        Sharpen
 	Threshold      float64
 	Gamma          float64
+	Brightness     float64
+	Contrast       float64
 	OutputICC      string
 	InputICC       string
 	Palette        bool
diff --git a/resizer.go b/resizer.go
index b4695d6..9af3116 100644
--- a/resizer.go
+++ b/resizer.go
@@ -142,6 +142,18 @@ func resizer(buf []byte, o Options) ([]byte, error) {
 		return nil, err
 	}
 
+	// Apply brightness, if necessary
+	image, err = applyBrightness(image, o)
+	if err != nil {
+		return nil, err
+	}
+
+	// Apply contrast, if necessary
+	image, err = applyContrast(image, o)
+	if err != nil {
+		return nil, err
+	}
+
 	return saveImage(image, o)
 }
 
@@ -610,3 +622,25 @@ func getAngle(angle Angle) Angle {
 	}
 	return Angle(math.Min(float64(angle), 270))
 }
+
+func applyBrightness(image *C.VipsImage, o Options) (*C.VipsImage, error) {
+	var err error
+	if o.Brightness != 0 {
+		image, err = vipsBrightness(image, o.Brightness)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return image, nil
+}
+
+func applyContrast(image *C.VipsImage, o Options) (*C.VipsImage, error) {
+	var err error
+	if o.Contrast > 0 {
+		image, err = vipsContrast(image, o.Contrast)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return image, nil
+}
diff --git a/vips.go b/vips.go
index 43990f3..650f090 100644
--- a/vips.go
+++ b/vips.go
@@ -830,3 +830,25 @@ func vipsGamma(image *C.VipsImage, Gamma float64) (*C.VipsImage, error) {
 	}
 	return out, nil
 }
+
+func vipsBrightness(image *C.VipsImage, brightness float64) (*C.VipsImage, error) {
+	var out *C.VipsImage
+	defer C.g_object_unref(C.gpointer(image))
+
+	err := C.vips_brightness_bridge(image, &out, C.double(brightness))
+	if err != 0 {
+		return nil, catchVipsError()
+	}
+	return out, nil
+}
+
+func vipsContrast(image *C.VipsImage, contrast float64) (*C.VipsImage, error) {
+	var out *C.VipsImage
+	defer C.g_object_unref(C.gpointer(image))
+
+	err := C.vips_contrast_bridge(image, &out, C.double(contrast))
+	if err != 0 {
+		return nil, catchVipsError()
+	}
+	return out, nil
+}
diff --git a/vips.h b/vips.h
index 190317c..6ded4a7 100644
--- a/vips.h
+++ b/vips.h
@@ -656,3 +656,13 @@ int vips_gamma_bridge(VipsImage *in, VipsImage **out, double exponent)
 {
   return vips_gamma(in, out, "exponent", 1.0 / exponent, NULL);
 }
+
+int vips_brightness_bridge(VipsImage *in, VipsImage **out, double k)
+{
+    return vips_linear1(in, out, 1.0 , k, NULL);
+}
+
+int vips_contrast_bridge(VipsImage *in, VipsImage **out, double k)
+{
+    return vips_linear1(in, out, k , 0.0, NULL);
+}