Implement adjustable histogram

5 files changed, 316 insertions, 106 deletions

diff --git a/src/uca-camera.c b/src/uca-camera.c
index 5684888..091ef54 100644
--- a/src/uca-camera.c
+++ b/src/uca-camera.c
@@ -128,7 +128,7 @@ uca_camera_set_property (GObject *object, guint property_id, const GValue *value
 static void
 uca_camera_get_property(GObject *object, guint property_id, GValue *value, GParamSpec *pspec)
 {
-    UcaCameraPrivate *priv = UCA_CAMERA_GET_PRIVATE(object);
+    UcaCameraPrivate *priv = UCA_CAMERA_GET_PRIVATE (object);
 
     switch (property_id) {
         case PROP_IS_RECORDING:
diff --git a/tools/gui/control.c b/tools/gui/control.c
index b36d188..214e4da 100644
--- a/tools/gui/control.c
+++ b/tools/gui/control.c
@@ -19,10 +19,7 @@
 #include <gtk/gtk.h>
 #include <gdk/gdk.h>
 #include <gdk/gdkkeysyms.h>
-#include <string.h>
-#include <time.h>
-#include <unistd.h>
-#include <errno.h>
+#include <math.h>
 
 #include "config.h"
 #include "uca-camera.h"
@@ -56,39 +53,28 @@ static UcaPluginManager *plugin_manager;
 
 
 static void
-convert_8bit_to_rgb (guchar *output, guchar *input, int width, int height)
+convert_8bit_to_rgb (guchar *output, guchar *input, gint width, gint height, gdouble min, gdouble max)
 {
+    gdouble factor = 255.0 / (max - min);
+
     for (int i = 0, j = 0; i < width*height; i++) {
-        output[j++] = input[i];
-        output[j++] = input[i];
-        output[j++] = input[i];
+        guchar val = (guchar) ((input[i] - min) * factor);
+        output[j++] = val;
+        output[j++] = val;
+        output[j++] = val;
     }
 }
 
 static void
-convert_16bit_to_rgb (guchar *output, guchar *input, int width, int height)
+convert_16bit_to_rgb (guchar *output, guchar *input, gint width, gint height, gdouble min, gdouble max)
 {
-    guint16 *in = (guint16 *) input;
-    guint16 min = G_MAXUINT16, max = 0;
-    gfloat spread = 0.0f;
-
-    for (int i = 0; i < width * height; i++) {
-        guint16 v = in[i];
-        if (v < min)
-            min = v;
-        if (v > max)
-            max = v;
-    }
-
-    spread = (gfloat) max - min;
+    gdouble factor = 255.0 / (max - min);
 
-    if (spread > 0.0f) {
-        for (int i = 0, j = 0; i < width*height; i++) {
-            guchar val = (guint8) (((in[i] - min) / spread) * 255.0f);
-            output[j++] = val;
-            output[j++] = val;
-            output[j++] = val;
-        }
+    for (int i = 0, j = 0; i < width*height; i++) {
+        guchar val = (guint8) ((input[i] - min) * factor);
+        output[j++] = val;
+        output[j++] = val;
+        output[j++] = val;
     }
 }
 
@@ -100,6 +86,9 @@ grab_thread (void *args)
     gint counter = 0;
 
     while (data->running) {
+        gdouble min_value;
+        gdouble max_value;
+
         uca_camera_grab (data->camera, (gpointer) &data->buffer, NULL);
 
         if (data->store) {
@@ -111,11 +100,12 @@ grab_thread (void *args)
 
         /* FIXME: We should actually check if this is really a new frame and
          * just do nothing if it is an already displayed one. */
+        egg_histogram_get_visible_range (EGG_HISTOGRAM_VIEW (data->histogram_view), &min_value, &max_value);
+
         if (data->pixel_size == 1)
-            convert_8bit_to_rgb (data->pixels, data->buffer, data->width, data->height);
-        else if (data->pixel_size == 2) {
-            convert_16bit_to_rgb (data->pixels, data->buffer, data->width, data->height);
-        }
+            convert_8bit_to_rgb (data->pixels, data->buffer, data->width, data->height, min_value, max_value);
+        else if (data->pixel_size == 2)
+            convert_16bit_to_rgb (data->pixels, data->buffer, data->width, data->height, min_value, max_value);
 
         gdk_threads_enter ();
 
@@ -221,6 +211,7 @@ create_main_window (GtkBuilder *builder, const gchar* camera_name)
     GdkPixbuf *pixbuf;
     GtkBox    *histogram_box;
     GtkContainer *scrolled_property_window;
+    GtkAdjustment *max_bin_adjustment;
     static ThreadData td;
 
     GError *error = NULL;
@@ -259,7 +250,8 @@ create_main_window (GtkBuilder *builder, const gchar* camera_name)
 
     histogram_box = GTK_BOX (gtk_builder_get_object (builder, "histogram-box"));
     gtk_box_pack_start (histogram_box, td.histogram_view, TRUE, TRUE, 6);
-    egg_histogram_view_set_data (EGG_HISTOGRAM_VIEW (td.histogram_view), td.buffer, td.width * td.height, bits_per_sample, 256);
+    egg_histogram_view_set_data (EGG_HISTOGRAM_VIEW (td.histogram_view),
+                                 td.buffer, td.width * td.height, bits_per_sample, 256);
 
     window = GTK_WIDGET (gtk_builder_get_object (builder, "window"));
     g_signal_connect (window, "destroy", G_CALLBACK (on_destroy), &td);
@@ -269,6 +261,16 @@ create_main_window (GtkBuilder *builder, const gchar* camera_name)
     td.record_button = GTK_WIDGET (gtk_builder_get_object (builder, "record-button"));
     set_tool_button_state (&td);
 
+    g_object_bind_property (gtk_builder_get_object (builder, "min_bin_value_adjustment"), "value",
+                            td.histogram_view, "minimum-bin-value",
+                            G_BINDING_DEFAULT);
+
+    max_bin_adjustment = GTK_ADJUSTMENT (gtk_builder_get_object (builder, "max_bin_value_adjustment"));
+    gtk_adjustment_set_value (max_bin_adjustment, pow (2, bits_per_sample) - 1);
+    g_object_bind_property (max_bin_adjustment, "value",
+                            td.histogram_view, "maximum-bin-value",
+                            G_BINDING_DEFAULT);
+
     g_signal_connect (td.start_button, "clicked", G_CALLBACK (on_start_button_clicked), &td);
     g_signal_connect (td.stop_button, "clicked", G_CALLBACK (on_stop_button_clicked), &td);
     g_signal_connect (td.record_button, "clicked", G_CALLBACK (on_record_button_clicked), &td);
diff --git a/tools/gui/control.glade b/tools/gui/control.glade
index 7ef712d..ebe2cc8 100644
--- a/tools/gui/control.glade
+++ b/tools/gui/control.glade
@@ -204,17 +204,97 @@
                           <placeholder/>
                         </child>
                         <child>
-                          <object class="GtkCheckButton" id="histogram-checkbutton">
-                            <property name="label" translatable="yes">Enable Live Update</property>
+                          <object class="GtkTable" id="table1">
                             <property name="visible">True</property>
-                            <property name="can_focus">True</property>
-                            <property name="receives_default">False</property>
                             <property name="border_width">6</property>
-                            <property name="active">True</property>
-                            <property name="draw_indicator">True</property>
+                            <property name="n_rows">3</property>
+                            <property name="n_columns">2</property>
+                            <property name="column_spacing">6</property>
+                            <property name="row_spacing">6</property>
+                            <child>
+                              <object class="GtkLabel" id="label2">
+                                <property name="visible">True</property>
+                                <property name="xalign">1</property>
+                                <property name="label" translatable="yes">Minimum Value:</property>
+                              </object>
+                              <packing>
+                                <property name="x_options">GTK_FILL</property>
+                                <property name="y_options"></property>
+                                <property name="x_padding">6</property>
+                                <property name="y_padding">6</property>
+                              </packing>
+                            </child>
+                            <child>
+                              <object class="GtkSpinButton" id="spinbutton1">
+                                <property name="width_request">100</property>
+                                <property name="visible">True</property>
+                                <property name="can_focus">True</property>
+                                <property name="invisible_char">•</property>
+                                <property name="adjustment">min_bin_value_adjustment</property>
+                              </object>
+                              <packing>
+                                <property name="left_attach">1</property>
+                                <property name="right_attach">2</property>
+                                <property name="x_options">GTK_EXPAND</property>
+                                <property name="y_options"></property>
+                              </packing>
+                            </child>
+                            <child>
+                              <object class="GtkLabel" id="label3">
+                                <property name="visible">True</property>
+                                <property name="xalign">1</property>
+                                <property name="label" translatable="yes">Maximum Value:</property>
+                              </object>
+                              <packing>
+                                <property name="top_attach">1</property>
+                                <property name="bottom_attach">2</property>
+                                <property name="x_options">GTK_FILL</property>
+                                <property name="y_options"></property>
+                                <property name="x_padding">6</property>
+                                <property name="y_padding">6</property>
+                              </packing>
+                            </child>
+                            <child>
+                              <object class="GtkSpinButton" id="spinbutton2">
+                                <property name="width_request">100</property>
+                                <property name="visible">True</property>
+                                <property name="can_focus">True</property>
+                                <property name="invisible_char">•</property>
+                                <property name="adjustment">max_bin_value_adjustment</property>
+                              </object>
+                              <packing>
+                                <property name="left_attach">1</property>
+                                <property name="right_attach">2</property>
+                                <property name="top_attach">1</property>
+                                <property name="bottom_attach">2</property>
+                                <property name="x_options">GTK_EXPAND</property>
+                                <property name="y_options"></property>
+                              </packing>
+                            </child>
+                            <child>
+                              <object class="GtkCheckButton" id="histogram-checkbutton">
+                                <property name="label" translatable="yes">Live Update</property>
+                                <property name="visible">True</property>
+                                <property name="can_focus">True</property>
+                                <property name="receives_default">False</property>
+                                <property name="border_width">6</property>
+                                <property name="active">True</property>
+                                <property name="draw_indicator">True</property>
+                              </object>
+                              <packing>
+                                <property name="top_attach">2</property>
+                                <property name="bottom_attach">3</property>
+                                <property name="x_options"></property>
+                                <property name="y_options"></property>
+                              </packing>
+                            </child>
+                            <child>
+                              <placeholder/>
+                            </child>
                           </object>
                           <packing>
-                            <property name="pack_type">end</property>
+                            <property name="expand">False</property>
+                            <property name="fill">False</property>
                             <property name="position">1</property>
                           </packing>
                         </child>
@@ -264,13 +344,6 @@
       </object>
     </child>
   </object>
-  <object class="GtkAdjustment" id="adjustment_scale">
-    <property name="value">65535</property>
-    <property name="lower">1</property>
-    <property name="upper">65535</property>
-    <property name="step_increment">1</property>
-    <property name="page_increment">10</property>
-  </object>
   <object class="GtkWindow" id="choice-window">
     <property name="border_width">6</property>
     <child>
@@ -352,4 +425,15 @@
       </object>
     </child>
   </object>
+  <object class="GtkAdjustment" id="min_bin_value_adjustment">
+    <property name="upper">65535</property>
+    <property name="step_increment">1</property>
+    <property name="page_increment">10</property>
+  </object>
+  <object class="GtkAdjustment" id="max_bin_value_adjustment">
+    <property name="value">256</property>
+    <property name="upper">65535</property>
+    <property name="step_increment">1</property>
+    <property name="page_increment">10</property>
+  </object>
 </interface>
diff --git a/tools/gui/egg-histogram-view.c b/tools/gui/egg-histogram-view.c
index 7abc2be..91e61e8 100644
--- a/tools/gui/egg-histogram-view.c
+++ b/tools/gui/egg-histogram-view.c
@@ -34,11 +34,14 @@ struct _EggHistogramViewPrivate
     /* This could be moved into a real histogram class */
     guint n_bins;
     gint *bins;
-    gint  min_value;
-    gint  max_value;
-    gint  min_border;
+    gint *grabbed;
+    gint  min_border;   /* threshold set in screen units */
     gint  max_border;
 
+    gdouble min_value;    /* lowest value of the first bin */
+    gdouble max_value;    /* highest value of the last bin */
+    gdouble range;
+
     gpointer data;
     gint     n_elements;
     gint     n_bits;
@@ -47,6 +50,8 @@ struct _EggHistogramViewPrivate
 enum
 {
     PROP_0,
+    PROP_MINIMUM_BIN_VALUE,
+    PROP_MAXIMUM_BIN_VALUE,
     N_PROPERTIES
 };
 
@@ -71,6 +76,7 @@ egg_histogram_view_set_data (EggHistogramView *view,
 {
     EggHistogramViewPrivate *priv;
 
+    g_return_if_fail (EGG_IS_HISTOGRAM_VIEW (view));
     priv = view->priv;
 
     if (priv->bins != NULL)
@@ -82,16 +88,46 @@ egg_histogram_view_set_data (EggHistogramView *view,
     priv->n_bits = n_bits;
     priv->n_elements = n_elements;
 
-    priv->min_value = 0;
+    priv->min_value = 0.0;
     priv->max_value = (gint) pow(2, n_bits) - 1;
 
-    priv->min_border = 20;
-    priv->max_border = priv->max_value - 20;
+    priv->min_border = 0;
+    priv->max_border = 256;
+    priv->range = priv->max_value - priv->min_value;
+}
+
+void
+egg_histogram_get_visible_range (EggHistogramView *view, gdouble *min, gdouble *max)
+{
+    EggHistogramViewPrivate *priv;
+    GtkAllocation allocation;
+    gdouble width;
+
+    g_return_if_fail (EGG_IS_HISTOGRAM_VIEW (view));
+
+    gtk_widget_get_allocation (GTK_WIDGET (view), &allocation);
+    width = (gdouble) allocation.width - 2 * BORDER;
+    priv = view->priv;
+
+    *min = (priv->min_border - 2) / width * priv->range;
+    *max = (priv->max_border - 2) / width * priv->range;
+}
+
+static void
+set_max_border (EggHistogramView *view)
+{
+    GtkAllocation allocation;
+
+    g_return_if_fail (EGG_IS_HISTOGRAM_VIEW (view));
+    gtk_widget_get_allocation (GTK_WIDGET (view), &allocation);
+    view->priv->max_border = allocation.width - 2 * BORDER;
 }
 
 static void
 compute_histogram (EggHistogramViewPrivate *priv)
 {
+    guint n_bins = priv->n_bins - 1;
+
     for (guint i = 0; i < priv->n_bins; i++)
         priv->bins[i] = 0;
 
@@ -100,8 +136,11 @@ compute_histogram (EggHistogramViewPrivate *priv)
 
         for (guint i = 0; i < priv->n_elements; i++) {
             guint8 v = data[i];
-            guint index = (guint) round (((gdouble) v) / priv->max_value * (priv->n_bins - 1));
-            priv->bins[index]++;
+
+            if (v >= priv->min_value && v <= priv->max_value) {
+                guint index = (guint) round (((gdouble) v) / priv->max_value * n_bins);
+                priv->bins[index]++;
+            }
         }
     }
     else if (priv->n_bits == 16) {
@@ -109,8 +148,11 @@ compute_histogram (EggHistogramViewPrivate *priv)
 
         for (guint i = 0; i < priv->n_elements; i++) {
             guint16 v = data[i];
-            guint index = (guint) floor (((gdouble ) v) / priv->max_value * (priv->n_bins - 1));
-            priv->bins[index]++;
+
+            if (v >= priv->min_value && v <= priv->max_value) {
+                guint index = (guint) floor (((gdouble ) v) / priv->max_value * n_bins);
+                priv->bins[index]++;
+            }
         }
     }
     else
@@ -137,6 +179,36 @@ egg_histogram_view_size_request (GtkWidget *widget,
     requisition->height = MIN_HEIGHT;
 }
 
+static void
+draw_bins (EggHistogramViewPrivate *priv,
+           cairo_t *cr,
+           gint width,
+           gint height)
+{
+    gdouble skip = ((gdouble) width) / priv->n_bins;
+    gdouble x = BORDER;
+    gdouble ys = height + BORDER - 1;
+    gint max_value = 0;
+
+    for (guint i = 0; i < priv->n_bins; i++) {
+        if (priv->bins[i] > max_value)
+            max_value = priv->bins[i];
+    }
+
+    if (max_value == 0)
+        return;
+
+    for (guint i = 0; i < priv->n_bins && x < (width - BORDER); i++, x += skip) {
+        if (priv->bins[i] == 0)
+            continue;
+
+        gint y = (gint) ((height - 2) * priv->bins[i]) / max_value;
+        cairo_move_to (cr, round (x), ys);
+        cairo_line_to (cr, round (x), ys - y);
+        cairo_stroke (cr);
+    }
+}
+
 static gboolean
 egg_histogram_view_expose (GtkWidget *widget,
                            GdkEventExpose *event)
@@ -146,7 +218,6 @@ egg_histogram_view_expose (GtkWidget *widget,
     GtkStyle *style;
     cairo_t *cr;
     gint width, height;
-    gint max_value = 0;
 
     priv = EGG_HISTOGRAM_VIEW_GET_PRIVATE (widget);
     cr = gdk_cairo_create (gtk_widget_get_window (widget));
@@ -181,36 +252,15 @@ egg_histogram_view_expose (GtkWidget *widget,
     /* Draw border areas */
     gdk_cairo_set_source_color (cr, &style->dark[GTK_STATE_NORMAL]);
 
-    if (priv->min_border > 0) {
-        cairo_rectangle (cr, BORDER, BORDER, priv->min_border + 0.5, height - 1);
-        cairo_fill (cr);
-    }
-
-    /* Draw spikes */
-    for (guint i = 0; i < priv->n_bins; i++) {
-        if (priv->bins[i] > max_value)
-            max_value = priv->bins[i];
-    }
+    cairo_rectangle (cr, BORDER, BORDER, priv->min_border + 0.5, height - 1);
+    cairo_fill (cr);
 
-    if (max_value == 0)
-        goto cleanup;
+    cairo_rectangle (cr, priv->max_border + 0.5, BORDER, width - priv->min_border - 0.5, height - 1);
+    cairo_fill (cr);
 
+    /* Draw spikes */
     gdk_cairo_set_source_color (cr, &style->black);
-
-    if (width > priv->n_bins) {
-        gdouble skip = ((gdouble) width) / priv->n_bins;
-        gdouble x = 1;
-
-        for (guint i = 0; i < priv->n_bins; i++, x += skip) {
-            if (priv->bins[i] == 0)
-                continue;
-
-            gint y = (gint) ((height - 2) * priv->bins[i]) / max_value;
-            cairo_move_to (cr, round (x + BORDER), height + BORDER - 1);
-            cairo_line_to (cr, round (x + BORDER), height + BORDER - 1 - y);
-            cairo_stroke (cr);
-        }
-    }
+    draw_bins (priv, cr, width, height);
 
 cleanup:
     cairo_destroy (cr);
@@ -242,9 +292,42 @@ egg_histogram_view_set_property (GObject *object,
                                  const GValue *value,
                                  GParamSpec *pspec)
 {
+    EggHistogramViewPrivate *priv;
+
     g_return_if_fail (EGG_IS_HISTOGRAM_VIEW (object));
+    priv = EGG_HISTOGRAM_VIEW_GET_PRIVATE (object);
 
     switch (property_id) {
+        case PROP_MINIMUM_BIN_VALUE:
+            {
+                gdouble v = g_value_get_double (value);
+
+                if (v > priv->max_value)
+                    g_warning ("Minimum value `%f' larger than maximum value `%f'",
+                               v, priv->max_value);
+                else {
+                    priv->min_value = v;
+                    priv->range = priv->max_value - v;
+                    priv->min_border = 0;
+                }
+            }
+            break;
+
+        case PROP_MAXIMUM_BIN_VALUE:
+            {
+                gdouble v = g_value_get_double (value);
+
+                if (v < priv->min_value)
+                    g_warning ("Maximum value `%f' larger than minimum value `%f'",
+                               v, priv->min_value);
+                else {
+                    priv->max_value = v;
+                    priv->range = v - priv->min_value;
+                    set_max_border (EGG_HISTOGRAM_VIEW (object));
+                }
+            }
+            break;
+
         default:
             G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
             return;
@@ -257,20 +340,48 @@ egg_histogram_view_get_property (GObject *object,
                                  GValue *value,
                                  GParamSpec *pspec)
 {
+    EggHistogramViewPrivate *priv;
+
     g_return_if_fail (EGG_IS_HISTOGRAM_VIEW (object));
+    priv = EGG_HISTOGRAM_VIEW_GET_PRIVATE (object);
 
     switch (property_id) {
+        case PROP_MINIMUM_BIN_VALUE:
+            g_value_set_double (value, priv->min_value);
+            break;
+
+        case PROP_MAXIMUM_BIN_VALUE:
+            g_value_set_double (value, priv->max_value);
+            break;
+
         default:
             G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
             return;
     }
 }
 
-static gint
-get_mouse_distance (EggHistogramViewPrivate *priv,
+static gboolean
+is_on_border (EggHistogramViewPrivate *priv,
+              gint x)
+{
+    gint d1 = (priv->min_border + BORDER) - x;
+    gint d2 = (priv->max_border + BORDER) - x;
+    return ABS (d1) < 6 || ABS (d2) < 6;
+}
+
+static gint *
+get_grabbed_border (EggHistogramViewPrivate *priv,
                     gint x)
 {
-    return (priv->min_border + BORDER) - x;
+    gint d1 = (priv->min_border + BORDER) - x;
+    gint d2 = (priv->max_border + BORDER) - x;
+
+    if (ABS (d1) < 6)
+        return &priv->min_border;
+    else if (ABS (d2) < 6)
+        return &priv->max_border;
+
+    return NULL;
 }
 
 static gboolean
@@ -284,13 +395,12 @@ egg_histogram_view_motion_notify (GtkWidget *widget,
     priv = view->priv;
 
     if (priv->grabbing) {
-        priv->min_border = event->x + BORDER;
+        *priv->grabbed = event->x;
+
         gtk_widget_queue_draw (widget);
     }
     else {
-        gint distance = get_mouse_distance (priv, event->x);
-
-        if (ABS(distance) < 6)
+        if (is_on_border (priv, event->x))
             set_cursor_type (view, GDK_FLEUR);
         else
             set_cursor_type (view, GDK_ARROW);
@@ -304,18 +414,10 @@ egg_histogram_view_button_release (GtkWidget *widget,
                                    GdkEventButton *event)
 {
     EggHistogramView *view;
-    EggHistogramViewPrivate *priv;
-    /* GtkAllocation allocation; */
-    /* gint width; */
-
-    /* gtk_widget_get_allocation (widget, &allocation); */
-    /* width  = allocation.width - 2 * BORDER; */
 
     view = EGG_HISTOGRAM_VIEW (widget);
-    priv = view->priv;
-
     set_cursor_type (view, GDK_ARROW);
-    priv->grabbing = FALSE;
+    view->priv->grabbing = FALSE;
 
     return TRUE;
 }
@@ -326,14 +428,13 @@ egg_histogram_view_button_press (GtkWidget *widget,
 {
     EggHistogramView *view;
     EggHistogramViewPrivate *priv;
-    gint distance;
 
     view = EGG_HISTOGRAM_VIEW (widget);
     priv = view->priv;
-    distance = get_mouse_distance (priv, event->x);
 
-    if (ABS (distance) < 6) {
+    if (is_on_border (priv, event->x)) {
         priv->grabbing = TRUE;
+        priv->grabbed = get_grabbed_border (priv, event->x);
         set_cursor_type (view, GDK_FLEUR);
     }
 
@@ -357,6 +458,23 @@ egg_histogram_view_class_init (EggHistogramViewClass *klass)
     widget_class->button_release_event = egg_histogram_view_button_release;
     widget_class->motion_notify_event  = egg_histogram_view_motion_notify;
 
+    egg_histogram_view_properties[PROP_MINIMUM_BIN_VALUE] =
+        g_param_spec_double ("minimum-bin-value",
+                             "Smallest possible bin value",
+                             "Smallest possible bin value, everything below is discarded.",
+                             0.0, G_MAXDOUBLE, 0.0,
+                             G_PARAM_READWRITE);
+
+    egg_histogram_view_properties[PROP_MAXIMUM_BIN_VALUE] =
+        g_param_spec_double ("maximum-bin-value",
+                             "Largest possible bin value",
+                             "Largest possible bin value, everything above is discarded.",
+                             0.0, G_MAXDOUBLE, 256.0,
+                             G_PARAM_READWRITE);
+
+    g_object_class_install_property (object_class, PROP_MINIMUM_BIN_VALUE, egg_histogram_view_properties[PROP_MINIMUM_BIN_VALUE]);
+    g_object_class_install_property (object_class, PROP_MAXIMUM_BIN_VALUE, egg_histogram_view_properties[PROP_MAXIMUM_BIN_VALUE]);
+
     g_type_class_add_private (klass, sizeof (EggHistogramViewPrivate));
 }
 
@@ -371,6 +489,8 @@ egg_histogram_view_init (EggHistogramView *view)
     priv->data = NULL;
     priv->n_bins = 0;
     priv->n_elements = 0;
+    priv->min_value = priv->min_border = 0;
+    priv->max_value = priv->max_border = 256;
 
     priv->cursor_type = GDK_ARROW;
     priv->grabbing = FALSE;
diff --git a/tools/gui/egg-histogram-view.h b/tools/gui/egg-histogram-view.h
index a1df0ba..61a1c8c 100644
--- a/tools/gui/egg-histogram-view.h
+++ b/tools/gui/egg-histogram-view.h
@@ -53,6 +53,10 @@ void          egg_histogram_view_set_data (EggHistogramView *view,
                                            guint             n_elements,
                                            guint             n_bits,
                                            guint             n_bins);
+void          egg_histogram_get_visible_range
+                                          (EggHistogramView *view,
+                                           gdouble          *min,
+                                           gdouble          *max);
 
 G_END_DECLS