Golang Canvas.Center方法代码示例

// Draw draws a plot to a draw.Canvas.
//
// Plotters are drawn in the order in which they were
// added to the plot.  Plotters that  implement the
// GlyphBoxer interface will have their GlyphBoxes
// taken into account when padding the plot so that
// none of their glyphs are clipped.
func (p *Plot) Draw(c draw.Canvas) {
	if p.BackgroundColor != nil {
		c.SetColor(p.BackgroundColor)
		c.Fill(c.Rectangle.Path())
	}
	if p.Title.Text != "" {
		c.FillText(p.Title.TextStyle, c.Center().X, c.Max.Y, -0.5, -1, p.Title.Text)
		c.Max.Y -= p.Title.Height(p.Title.Text) - p.Title.Font.Extents().Descent
		c.Max.Y -= p.Title.Padding
	}

	p.X.sanitizeRange()
	x := horizontalAxis{p.X}
	p.Y.sanitizeRange()
	y := verticalAxis{p.Y}

	ywidth := y.size()
	x.draw(padX(p, c.Crop(ywidth, 0, 0, 0)))
	xheight := x.size()
	y.draw(padY(p, c.Crop(0, xheight, 0, 0)))

	dataC := padY(p, padX(p, c.Crop(ywidth, xheight, 0, 0)))
	for _, data := range p.plotters {
		data.Plot(dataC, p)
	}

	p.Legend.draw(c.Crop(ywidth, 0, 0, 0).Crop(0, xheight, 0, 0))
}

// Thumbnail the thumbnail for the Line,
// implementing the plot.Thumbnailer interface.
func (pts *Line) Thumbnail(c *draw.Canvas) {
	if pts.ShadeColor != nil {
		points := []draw.Point{
			{c.Min.X, c.Min.Y},
			{c.Min.X, c.Max.Y},
			{c.Max.X, c.Max.Y},
			{c.Max.X, c.Min.Y},
		}
		poly := c.ClipPolygonY(points)
		c.FillPolygon(*pts.ShadeColor, poly)

		points = append(points, draw.Point{c.Min.X, c.Min.Y})
	} else {
		y := c.Center().Y
		c.StrokeLine2(pts.LineStyle, c.Min.X, y, c.Max.X, y)
	}
}

// draw draws the axis along the left side of a draw.Canvas.
func (a *verticalAxis) draw(c draw.Canvas) {
	x := c.Min.X
	if a.Label.Text != "" {
		x += a.Label.Height(a.Label.Text)
		c.Push()
		c.Rotate(math.Pi / 2)
		c.FillText(a.Label.TextStyle, c.Center().Y, -x, -0.5, 0, a.Label.Text)
		c.Pop()
		x += -a.Label.Font.Extents().Descent
	}
	marks := a.Tick.Marker.Ticks(a.Min, a.Max)
	if w := tickLabelWidth(a.Tick.Label, marks); len(marks) > 0 && w > 0 {
		x += w
	}
	major := false
	for _, t := range marks {
		y := c.Y(a.Norm(t.Value))
		if !c.ContainsY(y) || t.IsMinor() {
			continue
		}
		c.FillText(a.Tick.Label, x, y, -1, -0.5, t.Label)
		major = true
	}
	if major {
		x += a.Tick.Label.Width(" ")
	}
	if a.drawTicks() && len(marks) > 0 {
		len := a.Tick.Length
		for _, t := range marks {
			y := c.Y(a.Norm(t.Value))
			if !c.ContainsY(y) {
				continue
			}
			start := t.lengthOffset(len)
			c.StrokeLine2(a.Tick.LineStyle, x+start, y, x+len, y)
		}
		x += len
	}
	c.StrokeLine2(a.LineStyle, x, c.Min.Y, x, c.Max.Y)
}

// Thumbnail draws a line in the given style down the
// center of a DrawArea as a thumbnail representation
// of the LineStyle of the function.
func (f Function) Thumbnail(c *draw.Canvas) {
	y := c.Center().Y
	c.StrokeLine2(f.LineStyle, c.Min.X, y, c.Max.X, y)
}

// Thumbnail the thumbnail for the Scatter,
// implementing the plot.Thumbnailer interface.
func (pts *Scatter) Thumbnail(c *draw.Canvas) {
	c.DrawGlyph(pts.GlyphStyle, c.Center())
}