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, 4 insertions, 1 deletions

diff --git a/nsxiv.h b/nsxiv.h
index 7bf7e25..33a2bde 100644
--- a/nsxiv.h
+++ b/nsxiv.h
@@ -181,6 +181,8 @@ struct img {
 
 	Imlib_Color_Modifier cmod;
 	int gamma;
+	int brightness;
+	int contrast;
 
 	scalemode_t scalemode;
 	float zoom;
@@ -212,7 +214,8 @@ bool img_pan_edge(img_t*, direction_t);
 void img_rotate(img_t*, degree_t);
 void img_flip(img_t*, flipdir_t);
 void img_toggle_antialias(img_t*);
-bool img_change_gamma(img_t*, int);
+void img_update_color_modifiers(img_t*);
+bool img_change_color_modifier(img_t*, int, int*);
 bool img_frame_navigate(img_t*, int);
 bool img_frame_animate(img_t*);
 Imlib_Image img_open(const fileinfo_t*);