Select N colors from HSV color space.

This is as opposed to the three hard-coded RGB primaries which
we had before.

diff --git a/acre.c b/acre.c
index 35d0541d9c4b14bc58eef0da4d86bc61121be27a..bda8e81996c3e72cdfad5e634a7ddf132ee0902e 100644 (file)
--- a/acre.c
+++ b/acre.c
@@ -47,6 +47,12 @@ typedef struct _acre_axis {
     double max;
 } acre_axis_t;
 
+typedef struct _acre_color {
+    double red;
+    double green;
+    double blue;
+} acre_color_t;
+
 struct _acre {
     char *title;
     acre_axis_t x_axis;
@@ -59,7 +65,8 @@ struct _acre {
     /* Data for drawing. */
     cairo_t *cr;
     PangoFontDescription *font;
-    struct { double r; double g; double b;} colors[3];
+    acre_color_t *colors;
+    int colors_size;
     int num_colors;
 
     /* Total size including labels. */
@@ -92,6 +99,14 @@ acre_create (void)
     acre->data_size = 0;
     acre->num_data = 0;
 
+    acre->cr = NULL;
+    acre->font = NULL;
+    acre->colors = NULL;
+    acre->num_colors = 0;
+
+    acre->width = 0;
+    acre->height = 0;
+
     acre->chart.x = 0;
     acre->chart.y = 0;
     acre->chart.width = 0;
@@ -115,6 +130,8 @@ acre_destroy (acre_t *acre)
 
     free (acre->data);
 
+    free (acre->colors);
+
     free (acre);
 }
 
@@ -500,24 +517,76 @@ _compute_axis_ranges (acre_t *acre)
     cairo_restore (cr);
 }
 
+static void
+_acre_color_from_hsv (acre_color_t *color,
+                     double hue,
+                     double saturation,
+                     double value)
+{
+    double f, p, q, t;
+    int hmod6;
+
+    hmod6 = (int) floor (hue / 60) % 6;
+    f = hue / 60 - floor (hue / 60);
+    p = value * (1 - saturation);
+    q = value * (1 - f * saturation);
+    t = value * (1 - (1 - f) * saturation);
+    
+    switch (hmod6) {
+      case 0:
+       color->red = value;
+       color->green = t;
+       color->blue = p;
+       break;
+      case 1:
+       color->red = q;
+       color->green = value;
+       color->blue = p;
+       break;
+      case 2:
+       color->red = p;
+       color->green = value;
+       color->blue = t;
+       break;
+      case 3:
+       color->red = p;
+       color->green = q;
+       color->blue = value;
+       break;
+      case 4:
+       color->red = t;
+       color->green = p;
+       color->blue = value;
+       break;
+      case 5:
+       color->red = value;
+       color->green = p;
+       color->blue = q;
+       break;
+    }
+}
+
 static void
 _choose_colors (acre_t *acre)
 {
-    /* XXX: Should choose N, equally-spaced colors from a perceptually
-     * linear space here. */
-    acre->num_colors = 3;
+    double hue, saturation, value;
+    int i;
 
-    acre->colors[0].r = 1;
-    acre->colors[0].g = 0;
-    acre->colors[0].b = 0;
+    acre->num_colors = acre->num_data;
 
-    acre->colors[1].r = 0;
-    acre->colors[1].g = 1;
-    acre->colors[1].b = 0;
+    if (acre->num_colors > acre->colors_size) {
+       acre->colors_size = acre->num_colors;
+       acre->colors = xrealloc (acre->colors,
+                                acre->colors_size * sizeof (acre_color_t));
+    }
 
-    acre->colors[2].r = 0;
-    acre->colors[2].g = 0;
-    acre->colors[2].b = 1;
+    saturation = 1.0;
+    value = 0.7;
+    for (i = 0; i < acre->num_colors; i++) {
+       hue = 360 * (double) i / acre->num_colors;
+       _acre_color_from_hsv (&acre->colors[i],
+                             hue, saturation, value);
+    }
 }
 
 static void
@@ -536,9 +605,9 @@ _draw_data (acre_t *acre)
     for (d = 0; d < acre->num_data; d++) {
        int color = d % acre->num_colors;
        cairo_set_source_rgb (cr,
-                             acre->colors[color].r,
-                             acre->colors[color].g,
-                             acre->colors[color].b);
+                             acre->colors[color].red,
+                             acre->colors[color].green,
+                             acre->colors[color].blue);
        data = acre->data[d];
        cairo_new_path (cr);
        for (i = 0; i < data->num_points; i++) {
@@ -680,13 +749,14 @@ _draw_legend (acre_t *acre)
     cairo_translate (cr, ACRE_LEGEND_PAD, ACRE_LEGEND_PAD);
 
     for (i = 0; i < acre->num_data; i++) {
-       cairo_move_to (cr, 0, ACRE_FONT_SIZE / 2 + 0.5);
-       cairo_rel_line_to (cr, ACRE_LEGEND_LINE_SIZE, 0);
+       cairo_rectangle (cr,
+                        0, ACRE_LEGEND_LINE_SIZE / 2,
+                        ACRE_LEGEND_LINE_SIZE, ACRE_LEGEND_LINE_SIZE / 2);
        cairo_set_source_rgb (cr,
-                             acre->colors[i % acre->num_colors].r,
-                             acre->colors[i % acre->num_colors].g,
-                             acre->colors[i % acre->num_colors].b);
-       cairo_stroke (cr);
+                             acre->colors[i % acre->num_colors].red,
+                             acre->colors[i % acre->num_colors].green,
+                             acre->colors[i % acre->num_colors].blue);
+       cairo_fill (cr);
 
        layout = _create_layout (acre, acre->data[i]->name);
        cairo_move_to (cr, ACRE_LEGEND_LINE_SIZE + ACRE_LEGEND_PAD, 0);