概述

图表缩放指的是局部放大或缩小图表，可以更方便的查看图表数据。

FlexChart支持两种方式缩放，缩放（zoom）和平移（panning）

本文主要来讲书第一种的缩放模式-缩放，很好理解就是我们选中区域将我们选中的series进行放大，包括对应的的X轴，Y轴以及刻度值一起来放大，来达到我们的放大效果。

首先我们要扑捉三个事件：MouseDown、MouseMove、MouseUp，

在MouseDown中我们需要记录一下鼠标起始点的位置的点坐标pStart

在MouseMove中我需要来记录选中的区域，来标记我们选中的范围，并画出矩形Rectangle

在MouseUp中我最后一次更新鼠标点的位置，并且

1:

   2:          private void PerformZoom(Point ptStart, Point ptLast)

   3:          {

   4:              // Convert points to data coordinates

   5:              var p1 = flexChart1.PointToData(ptStart);

   6:              var p2 = flexChart1.PointToData(ptLast);

   7:              flexChart1.BeginUpdate();

   8:              // Update axes with new limits

   9:              flexChart1.AxisX.Min = Math.Min(p1.X, p2.X);

  10:              flexChart1.AxisY.Min = Math.Min(p1.Y, p2.Y);

  11:              flexChart1.AxisX.Max = Math.Max(p1.X, p2.X);

  12:              flexChart1.AxisY.Max = Math.Max(p1.Y, p2.Y);

  13:              flexChart1.EndUpdate();

  14:          }

  15:          public void ChartMouseDown(Object sender, MouseEventArgs e)

  16:          {

  17:              // Start zooming

  18:              zooming = true;

  19:              // Save starting point of selection rectangle

  20:              ptStart.X = e.X;

  21:              ptStart.Y = e.Y;

  22:              ptLast = Point.Empty;

  23:          }

  24:          public void ChartMouseMove(Object sender, MouseEventArgs e)

  25:          {

  26:              // When zooming update selection range

  27:              if (zooming)

  28:              {

  29:                  Point ptCurrent = new Point(e.X, e.Y);

  30:                  // Undraw old frame

  31:                  if (!ptLast.IsEmpty)

  32:                      DrawReversibleRectangle(ptStart, ptLast);

  33:                  // Update last point

  34:                  ptLast = ptCurrent;

  35:                  // Draw new frame

  36:                  DrawReversibleRectangle(ptStart, ptCurrent);

  37:              }

  38:          }

39:

  40:          public void ChartMouseUp(Object sender, MouseEventArgs e)

  41:          {

  42:              // End zooming

  43:              zooming = false;

  44:              // Redraw frame to restore screen

  45:              if (!ptLast.IsEmpty)

  46:              {

  47:                  Point ptCurrent = new Point(e.X, e.Y);

  48:                  DrawReversibleRectangle(ptStart, ptLast);

  49:              }

  50:              PerformZoom(ptStart, ptLast);

  51:              // Clean up

  52:              ptStart = ptLast = Point.Empty;

  53:          }

Demo:\Documents\ComponentOne Samples\WinForms\C1FlexChart\CS\FlexChartExplorer

如果你有疑问，可以到GCDN获得技术支持：

官方网站：/developer

FlexChart Zoom(一)