add brightness and contrast (#396)

* Imlib2 supports modifying gamma, brightness and contrast directly
  while sxiv only supports gamma. Makes sense to extend it to brightness
  and contrast as well.

* Since color corrections need to be aware of each other, they have been
  refactored into one centralized function.

* This also makes the code more hackable as it makes it easier to add
  more color correction functions without them interfering with each
  other.

Co-authored-by: 0ion9 <finticemo@gmail.com>
Co-authored-by: NRK <nrk@disroot.org>
Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/396
Reviewed-by: NRK <nrk@disroot.org>
Reviewed-by: TAAPArthur <taaparthur@noreply.codeberg.org>
Co-authored-by: Berke Kocaoğlu <kberke@metu.edu.tr>
Co-committed-by: Berke Kocaoğlu <kberke@metu.edu.tr>

1 files changed, 20 insertions, 7 deletions

diff --git a/commands.c b/commands.c
index 3cc921c..1ba0363 100644
--- a/commands.c
+++ b/commands.c
@@ -222,15 +222,28 @@ bool cg_navigate_marked(arg_t n)
 	return navigate_to(new);
 }
 
-bool cg_change_gamma(arg_t d)
+static bool change_color_modifier(arg_t d, int *target)
 {
-	if (img_change_gamma(&img, d * (prefix > 0 ? prefix : 1))) {
-		if (mode == MODE_THUMB)
-			tns.dirty = true;
-		return true;
-	} else {
+	if (!img_change_color_modifier(&img, d * (prefix > 0 ? prefix : 1), target))
 		return false;
-	}
+	if (mode == MODE_THUMB)
+		tns.dirty = true;
+	return true;
+}
+
+bool cg_change_gamma(arg_t d)
+{
+	return change_color_modifier(d, &img.gamma);
+}
+
+bool cg_change_brightness(arg_t d)
+{
+	return change_color_modifier(d, &img.brightness);
+}
+
+bool cg_change_contrast(arg_t d)
+{
+	return change_color_modifier(d, &img.contrast);
 }
 
 bool ci_navigate(arg_t n)