From 8cbf46d78e70a9f678e8d4d65c1a4e2f61db4ea0 Mon Sep 17 00:00:00 2001
From: Stefan Jahn <stefan@gruft.de>
Date: Sat, 26 Nov 2022 02:44:45 +0100
Subject: [PATCH] Added zoom functionality in histogram

---
 histogram.cc | 89 +++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 75 insertions(+), 14 deletions(-)

diff --git a/histogram.cc b/histogram.cc
index e576421..fab6b82 100644
--- a/histogram.cc
+++ b/histogram.cc
@@ -4,21 +4,32 @@
  *
  *****************************************************************************************/
 
+#include <math.h>
+
 #include "simpleskycam.h"
 #include "histogram.h"
 #include "gui.h"
 #include "configuration.h"
 #include "video.h"
 
+#define HISTOGRAM_WIDTH 256
+#define HISTOGRAM_MARGIN 16
 
 GtkWidget *histogram_da = NULL;
-int histogram[3][256];    		// 6* hist_width min, max, min , max.....
+int histogram[3][HISTOGRAM_WIDTH];	// 6* hist_width min, max, min , max.....
 int histogram_max;				// max vlaue
+int histogram_zoom_start = 0;           // first zoom value
+int histogram_zoom_stop = HISTOGRAM_WIDTH; // second zoom value
+int histogram_x;                        // current mouse x-coordinate 
+int histogram_pressed_x;                // window x-coordinate when pressing a button
+int histogram_released_x;               // window x-coordinate when releasing a button
+int histogram_pressed = 0;              // indicates button pressed or not
+int histogram_zoomed = 0;               // indicates zoom
 
 extern GtkBuilder *_builder_;			// work around for threads
 
 void cb_histogramda_draw(GtkWidget *area, cairo_t *cr, int w, int h, gpointer data) {
-	int clientw, clienth, px, py2;
+  int clientw, clienth, px, px2, py2;
 	GdkRGBA color;
 	char txt[255];
 
@@ -57,15 +68,29 @@ void cb_histogramda_draw(GtkWidget *area, cairo_t *cr, int w, int h, gpointer da
 		}
 		gdk_cairo_set_source_rgba(cr, &color);
 
-    	for (int i = 0; i < 256; i++) {
-			px = 16 + ((clientw-32) * i) / 256;
-			py2 = (clienth-16) - ((clienth-32) * histogram[chan][i]) / histogram_max;
+		int histogram_width = histogram_zoom_stop - histogram_zoom_start;
+    	for (int i = 0; i < histogram_width; i++) {
+			px = HISTOGRAM_MARGIN + ((clientw-HISTOGRAM_MARGIN*2) * i) / histogram_width;
+			py2 = (clienth-HISTOGRAM_MARGIN) - ((clienth-HISTOGRAM_MARGIN*2) * histogram[chan][histogram_zoom_start+i]) / histogram_max;
 
     		if (i == 0) cairo_move_to(cr, px, py2);
     		else 		cairo_line_to(cr, px, py2);
 
     	}
 		cairo_stroke(cr);
+
+		if (histogram_pressed) {
+		  if (histogram_pressed_x < histogram_x) {
+		    px = histogram_pressed_x;
+		    px2 = histogram_x;
+		  } else {
+		    px2 = histogram_pressed_x;
+		    px = histogram_x;
+		  }
+		  cairo_set_source_rgba(cr, 0.5, 0.5, 0.5, 0.5);
+		  cairo_rectangle (cr, px, 0, px2-px, clienth);
+		  cairo_fill (cr);
+		}
     }
 
 	// draw some text
@@ -122,8 +147,8 @@ void histogram_update(VideoFrame *vf) {
 	if (vf == NULL) return;
 	if (vf->w <= 0 ) return;
 
-	for (chan = 0; chan < 3; chan++) for (i = 0; i < 256; i++)
-		histogram[chan][i] = 0;
+	// initialize histogram
+	memset (histogram, 0, sizeof(histogram));
 
 	for (i = 0, x = 0; x < vf->w; x++) {
 		for (y = 0; y < vf->h; y++) {
@@ -136,25 +161,61 @@ void histogram_update(VideoFrame *vf) {
 	if (histogram_da)
 		gdk_window_invalidate_rect(gtk_widget_get_window(histogram_da), NULL, true);
 
-	for (histogram_max = 0, chan = 0; chan < 3; chan++) for (i = 0; i < 256; i++)
+	for (histogram_max = 0, chan = 0; chan < 3; chan++) for (i = 0; i < HISTOGRAM_WIDTH; i++)
 		if (histogram_max < histogram[chan][i]) histogram_max = histogram[chan][i];
 };
 
 
 
 void cb_histogramda_motion (GtkWidget *widget, GdkEvent *event, gpointer data) {
-//	printf ("%s:%d %s\n", __FILE__, __LINE__, __FUNCTION__);
+  if(!histogram_zoomed) {
+    histogram_x = (int)round(event->button.x);
+  }
 };
 
 
 void cb_histogramda_btnpress (GtkWidget *widget, gpointer data) {
-	printf ("%s:%d %s\n", __FILE__, __LINE__, __FUNCTION__);
+  if (!histogram_zoomed) {
+    if (!histogram_pressed) {
+      histogram_pressed = 1;
+      histogram_pressed_x = histogram_x;
+    }
+  } else {
+    histogram_zoomed = 0;
+    histogram_zoom_start = 0;
+    histogram_zoom_stop = HISTOGRAM_WIDTH;
+  }
 };
 
 
 void cb_histogramda_btnrelease (GtkWidget *widget, gpointer data) {
-	printf ("%s:%d %s\n", __FILE__, __LINE__, __FUNCTION__);
+  if (!histogram_zoomed) {
+    if (histogram_pressed) {
+      histogram_pressed = 0;
+      histogram_released_x = histogram_x;
+      histogram_zoomed = 1;
+
+      // here we need to compute start/stop coordinates inside histogram
+      int clientw;
+      clientw = gtk_widget_get_allocated_width(histogram_da);
+
+      // translate first coordinate
+      histogram_zoom_start = (histogram_pressed_x - HISTOGRAM_MARGIN) * HISTOGRAM_WIDTH / (clientw - HISTOGRAM_MARGIN*2);
+      if (histogram_zoom_start < 0) histogram_zoom_start = 0;
+      if (histogram_zoom_start > 256) histogram_zoom_start = 256;
+
+      // translate second coordinate
+      histogram_zoom_stop = (histogram_released_x - HISTOGRAM_MARGIN) * HISTOGRAM_WIDTH / (clientw - HISTOGRAM_MARGIN*2) + 1;
+      // limit the values
+      if (histogram_zoom_stop < 0) histogram_zoom_stop = 0;
+      if (histogram_zoom_stop > 256) histogram_zoom_stop = 256;
+
+      // exchange the values if necessary
+      if (histogram_zoom_start > histogram_zoom_stop) {
+	int t = histogram_zoom_start;
+	histogram_zoom_start = histogram_zoom_stop;
+	histogram_zoom_stop = t;
+      }
+    }
+  }
 };
-
-
-