Class | Gruff::Pie |
In: |
lib/gruff/pie.rb
|
Parent: | Gruff::Base |
Here‘s how to make a Pie graph:
g = Gruff::Pie.new g.title = "Visual Pie Graph Test" g.data 'Fries', 20 g.data 'Hamburgers', 50 g.write("test/output/pie_keynote.png")
To control where the pie chart starts creating slices, use zero_degree.
TEXT_OFFSET_PERCENTAGE | = | 0.15 |
zero_degree | [RW] | Can be used to make the pie start cutting slices at the top (-90.0) or at another angle. Default is 0.0, which starts at 3 o‘clock. |
# File lib/gruff/pie.rb, line 27 27: def draw 28: @hide_line_markers = true 29: 30: super 31: 32: return unless @has_data 33: 34: diameter = @graph_height 35: radius = ([@graph_width, @graph_height].min / 2.0) * 0.8 36: top_x = @graph_left + (@graph_width - diameter) / 2.0 37: center_x = @graph_left + (@graph_width / 2.0) 38: center_y = @graph_top + (@graph_height / 2.0) - 10 # Move graph up a bit 39: total_sum = sums_for_pie() 40: prev_degrees = @zero_degree 41: 42: # Use full data since we can easily calculate percentages 43: data = (@sort ? @data.sort{ |a, b| a[DATA_VALUES_INDEX].first <=> b[DATA_VALUES_INDEX].first } : @data) 44: data.each do |data_row| 45: if data_row[DATA_VALUES_INDEX].first > 0 46: @d = @d.stroke data_row[DATA_COLOR_INDEX] 47: @d = @d.fill 'transparent' 48: @d.stroke_width(radius) # stroke width should be equal to radius. we'll draw centered on (radius / 2) 49: 50: current_degrees = (data_row[DATA_VALUES_INDEX].first / total_sum) * 360.0 51: 52: # ellipse will draw the the stroke centered on the first two parameters offset by the second two. 53: # therefore, in order to draw a circle of the proper diameter we must center the stroke at 54: # half the radius for both x and y 55: @d = @d.ellipse(center_x, center_y, 56: radius / 2.0, radius / 2.0, 57: prev_degrees, prev_degrees + current_degrees + 0.5) # <= +0.5 'fudge factor' gets rid of the ugly gaps 58: 59: half_angle = prev_degrees + ((prev_degrees + current_degrees) - prev_degrees) / 2 60: 61: # Following line is commented to allow display of the percentiles 62: # bug appeared between r90 and r92 63: # unless @hide_line_markers then 64: # End the string with %% to escape the single %. 65: # RMagick must use sprintf with the string and % has special significance. 66: label_string = ((data_row[DATA_VALUES_INDEX].first / total_sum) * 67: 100.0).round.to_s + '%%' 68: @d = draw_label(center_x,center_y, half_angle, 69: radius + (radius * TEXT_OFFSET_PERCENTAGE), 70: label_string) 71: # end 72: 73: prev_degrees += current_degrees 74: end 75: end 76: 77: # TODO debug a circle where the text is drawn... 78: 79: @d.draw(@base_image) 80: end
Labels are drawn around a slightly wider ellipse to give room for labels on the left and right.
# File lib/gruff/pie.rb, line 87 87: def draw_label(center_x, center_y, angle, radius, amount) 88: # TODO Don't use so many hard-coded numbers 89: r_offset = 20.0 # The distance out from the center of the pie to get point 90: x_offset = center_x # + 15.0 # The label points need to be tweaked slightly 91: y_offset = center_y # This one doesn't though 92: radius_offset = (radius + r_offset) 93: ellipse_factor = radius_offset * 0.15 94: x = x_offset + ((radius_offset + ellipse_factor) * Math.cos(angle.deg2rad)) 95: y = y_offset + (radius_offset * Math.sin(angle.deg2rad)) 96: 97: # Draw label 98: @d.fill = @font_color 99: @d.font = @font if @font 100: @d.pointsize = scale_fontsize(@marker_font_size) 101: @d.stroke = 'transparent' 102: @d.font_weight = BoldWeight 103: @d.gravity = CenterGravity 104: @d.annotate_scaled( @base_image, 105: 0, 0, 106: x, y, 107: amount, @scale) 108: end