Add grid to bar histogram, simplify the code and draw horizontal line…

…s too.

src/histogram.c

@@ -41,8 +41,10 @@ struct _HistMap {
 struct _Histogram {
 	gint histogram_chan;
 	gint histogram_logmode;
-};
+	guint histogram_vgrid; /* number of vertical divisions, 0 for none */
+	guint histogram_hgrid; /* number of horizontal divisions, 0 for none */
 
+};
 
 Histogram *histogram_new(void)
 {
@@ -51,6 +53,8 @@ Histogram *histogram_new(void)
 	histogram = g_new0(Histogram, 1);
 	histogram->histogram_chan = options->histogram.last_channel_mode;
 	histogram->histogram_logmode = options->histogram.last_log_mode;
+	histogram->histogram_vgrid = 5;
+	histogram->histogram_hgrid = 3;
 
 	return histogram;
 }
@@ -166,6 +170,44 @@ const HistMap *histmap_get(FileData *fd)
 	return NULL;
 }
 
+static void histogram_vgrid(Histogram *histogram, GdkPixbuf *pixbuf, gint x, gint y, gint width, gint height)
+{
+	static gint c = 160;
+	static gint alpha = 250;
+	guint i;
+	float add;
+
+	if (histogram->histogram_vgrid == 0) return;
+
+	add = width / (float)histogram->histogram_vgrid;
+
+	for (i = 1; i < histogram->histogram_vgrid; i++)
+		{
+		gint xpos = x + (int)(i * add + 0.5);
+
+		pixbuf_draw_line(pixbuf, x, y, width, height, xpos, y, xpos, y + height, c, c, c, alpha);
+		}
+}
+
+static void histogram_hgrid(Histogram *histogram, GdkPixbuf *pixbuf, gint x, gint y, gint width, gint height)
+{
+	static gint c = 160;
+	static gint alpha = 250;
+	guint i;
+	float add;
+
+	if (histogram->histogram_hgrid == 0) return;
+
+	add = height / (float)histogram->histogram_hgrid;
+
+	for (i = 1; i < histogram->histogram_hgrid; i++)
+		{
+		gint ypos = y + (int)(i * add + 0.5);
+
+		pixbuf_draw_line(pixbuf, x, y, width, height, x, ypos, x + width, ypos, c, c, c, alpha);
+		}
+}
+
 gint histogram_draw(Histogram *histogram, const HistMap *histmap, GdkPixbuf *pixbuf, gint x, gint y, gint width, gint height)
 {
 	/* FIXME: use the coordinates correctly */
@@ -174,6 +216,10 @@ gint histogram_draw(Histogram *histogram, const HistMap *histmap, GdkPixbuf *pix
 	gdouble logmax;
 
 	if (!histogram || !histmap) return 0;
+
+	/* Draw the grid */
+	histogram_vgrid(histogram, pixbuf, x, y, width, height);
+	histogram_hgrid(histogram, pixbuf, x, y, width, height);
 
 	for (i = 0; i < 1024; i++) {
 #if 0

src/image-overlay.c

@@ -640,21 +640,8 @@ static GdkPixbuf *image_osd_info_render(OverlayStateData *osd)
 			gint x = 5;
 			gint y = height - HISTOGRAM_HEIGHT - 5;
 			gint w = width - 10;
-			float xoffset = 0;
-			gint subdiv = 5;
-			gint c = 160;
-			gint alpha = 250;
-			gint i;
-			float add = w / (float)subdiv;
-
-			for (i = 0; i < subdiv; i++)
-				{
-				gint d = (i > 0 ? 0 : 1);
 
-				pixbuf_set_rect(pixbuf, x + xoffset + 0.5, y, add + d + 0.5, HISTOGRAM_HEIGHT, c, c, c, alpha, d, 1, 1, 1);
-				xoffset += add+d;
-				}
-
+			pixbuf_set_rect_fill(pixbuf, x, y, w, HISTOGRAM_HEIGHT, 220, 220, 220, 210);
 			histogram_draw(osd->histogram, histmap, pixbuf, x, y, w, HISTOGRAM_HEIGHT);
 			}
 		pixbuf_draw_layout(pixbuf, layout, imd->pr, 5, 5, 0, 0, 0, 255);