func (ac ActivityChart) GetBackgroundStyle() chart.Style {
	return ac.Background.InheritFrom(ac.styleDefaultsBackground())
}
GetBackgroundStyle returns the chart background style or the default value
package main
import (
	"errors"
	"fmt"
	"io"
	"github.com/golang/freetype/truetype"
	"github.com/wcharczuk/go-chart"
	"github.com/wcharczuk/go-chart/drawing"
	"github.com/wcharczuk/go-chart/util"
)
const daysPerWeek = 7
var activityChartDefaultColors = []drawing.Color{
	drawing.ColorFromHex("ebedf0"),
	drawing.ColorFromHex("c6e48b"),
	drawing.ColorFromHex("7bc96f"),
	drawing.ColorFromHex("239a3b"),
	drawing.ColorFromHex("196127"),
}
var activityChartDayLabels = []string{"Mon", "", "Wed", "", "Fri", "", "Sun"}
var activityChartMonthLabels = []string{"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}
type ActivityChart struct {
	Title      string
	TitleStyle chart.Style
	ColorPalette chart.ColorPalette
	Width  int
	Height int
	DPI    float64
	DotSize    int
	DotSpacing int
	Background chart.Style
	Canvas     chart.Style
	Font        *truetype.Font
	defaultFont *truetype.Font
	XAxis  chart.Style
	YAxis  chart.Style
	Legend chart.Style
	Days         []int
	CurrentDay   int  
	CurrentMonth int  
	RightToLeft  bool
	titleX      int
	titleY      int
	chartX      int
	chartY      int
	chartWidth  int
	chartHeight int
	numWeeks    int
	maxValue    int
}
func (ac ActivityChart) GetColorPalette() chart.ColorPalette {
	if ac.ColorPalette != nil {
		return ac.ColorPalette
	}
	return chart.AlternateColorPalette
}
func (ac ActivityChart) GetWidth() int {
	if ac.Width == 0 {
		return chart.DefaultChartWidth
	}
	return ac.Width
}
func (ac ActivityChart) GetHeight() int {
	if ac.Height == 0 {
		return chart.DefaultChartHeight
	}
	return ac.Height
}
func (ac ActivityChart) GetDPI() float64 {
	if ac.DPI == 0 {
		return chart.DefaultDPI
	}
	return ac.DPI
}
func (ac ActivityChart) GetDotSize() int {
	if ac.DotSize == 0 {
		return 16
	}
	return ac.DotSize
}
func (ac ActivityChart) GetDotSpacing() int {
	if ac.DotSpacing == 0 {
		return 2
	}
	return ac.DotSpacing
}