private void fungraph_GetFunctionValueRange(Expression fx, double x0, double rx, int i0, int i1, out double y0, out double y1)
{
// 函数值的取值范围
y0 = double.MaxValue;
y1 = double.MinValue;
for (int i = i0; i <= i1; i++)
{
double x = x0 + (i - i0) * rx;
double y = fx.Compute(x);
if (double.IsInfinity(y) || double.IsNaN(y))
{
continue;
}
if (y0 > y)
{
y0 = y;
}
if (y1 < y)
{
y1 = y;
}
}
}
private bool draw_fungraph(string fuuuus)
{
//绘制函数
if (fuuuus.StartsWith("f(x)="))
{
fuuuus = fuuuus.Remove(0, 5);
}
if (fungraph_needrsdaw || lastEnterGy != fuuuus)
{
string fun = fuuuus;
if (lastEnterGy != fuuuus || lastEnterGy == "")
{
lastEnterGy = fuuuus;
fungraph_dawing = true;
if (fun.Contains("sin(") && !fun.Contains("asin("))
{
fun = fun.Replace("sin(", "Math.Sin(");
}
if (fun.Contains("cos(") && !fun.Contains("acos("))
{
fun = fun.Replace("cos(", "Math.Cos(");
}
if (fun.Contains("tan(") && !fun.Contains("atan("))
{
fun = fun.Replace("tan(", "Math.Tan(");
}
if (fun.Contains("asin("))
{
fun = fun.Replace("asin(", "Math.Asin(");
}
if (fun.Contains("acos("))
{
fun = fun.Replace("acos(", "Math.Acos(");
}
if (fun.Contains("atan("))
{
fun = fun.Replace("atan(", "Math.Atan(");
}
if (fun.Contains("pow("))
{
fun = fun.Replace("pow(", "Math.Pow(");
}
if (fun.Contains("lg("))
{
fun = fun.Replace("lg(", "Math.Log10(");
}
if (fun.Contains("log("))
{
fun = fun.Replace("log(", "Math.Log(");
}
if (fun.Contains("ln("))
{
fun = fun.Replace("ln(", "Math.Log(");
}
if (fun.Contains("sqrt("))
{
fun = fun.Replace("sqrt(", "Math.Sqrt(");
}
if (fun.Contains("ln("))
{
fun = fun.Replace("ln(", "Math.Log(");
}
if (fun.Contains("π"))
{
fun = fun.Replace("π", "Math.PI");
}
if (fun.Contains("pi"))
{
fun = fun.Replace("pi", "Math.PI");
}
if (fun.Contains("e"))
{
fun = fun.Replace("e", "Math.E");
}
lock (fungraph)
{
Graphics gc = Graphics.FromImage(fungraph);
gc.Clear(Color.White);
try
{
if (fun == "")
{
throw new Exception("请输入需要绘制的函数！");
}
else if (!fun.Contains("x"))
{
throw new Exception("未找到自变量x");
}
double x0 = new Expression(fungraph_str_to_xy(tbxX0.Text)).Compute(0);
double x1 = new Expression(fungraph_str_to_xy(tbxX1.Text)).Compute(0);
if (x1 <= x0)
{
throw new Exception("区间设置有误。请保证区间 结束>开始 。");
}
Size size = panel_fungraph.Size;
int i0 = 0;
int i1 = size.Width - 1;
int j0 = fungraph_title_height;// 屏幕保留区域的高度
int j1 = size.Height - 1;
Pen pen = new Pen(Color.Black, 1);
//gc.DrawLine(pen, i0, j0, i1, j0); // 画图区和保留区的分界线
double rx = (x1 - x0) / (i1 - i0);
double y0, y1;
Expression fx = new Expression(fun);
fungraph_GetFunctionValueRange(fx, x0, rx, i0, i1, out y0, out y1);
double ry = (y1 - y0) / (j1 - j0);
if (check_fungr_data.Checked)
{
fungraph_Out(gc, 1, "f(x): " + fun);
fungraph_Out(gc, 3, "x:[{0}, {1}] ({2})", fungraph_xy_to_str(x0), fungraph_xy_to_str(x1), fungraph_xy_to_str(x1 - x0));
fungraph_Out(gc, 4, "y:[{0}, {1}] ({2})", fungraph_xy_to_str(y0), fungraph_xy_to_str(y1), fungraph_xy_to_str(y1 - y0));
fungraph_Out(gc, 6, "rx:{0}", (1 / rx).ToString("0.0000")); // 函数自变量每单位值用多少个象素表示
fungraph_Out(gc, 7, "ry:{0}", (1 / ry).ToString("0.0000")); // 函数的值每单位值用多少个象素表示
fungraph_Out(gc, 8, "r :{0}", (rx / ry).ToString("0.0000")); // 该值如果小于1表示图形纵向被压扁，反之则被拉伸
}
pen.Color = Color.Green;
int j = j1 + (int)(y0 / ry);
if (j >= j0 && j <= j1)
{
if (check_fg_drawxy.Checked)
{
gc.DrawLine(pen, i0, j, i1, j); // x坐标轴
gc.DrawString(fungraph_xy_to_str(x0), new Font("Courier New", 10), Brushes.Black, 0, j - 15);
gc.DrawString("0", new Font("Courier New", 10), Brushes.Blue, size.Width / 2, j - 15);
gc.DrawString(fungraph_xy_to_str(x1), new Font("Courier New", 10), Brushes.Black, new Rectangle(size.Width - 30, j - 15, 30, 15), new StringFormat()
{
LineAlignment = StringAlignment.Center, Alignment = StringAlignment.Far
});
}
else
{
pen.Color = Color.Silver;
gc.DrawLine(pen, i0, j, i1, j); // x坐标轴
}
}
int i = i0 - (int)(x0 / rx);
if (i >= i0 && i <= i1)
{
if (check_fg_drawxy.Checked)
{
gc.DrawLine(pen, i, j0, i, j1); // y坐标轴
gc.DrawString(fungraph_xy_to_str(y1), new Font("Courier New", 10), Brushes.Black, i + 1, fungraph_title_height);
gc.DrawString(fungraph_xy_to_str(y0), new Font("Courier New", 10), Brushes.Black, i + 1, j1 - 15);
}
else
{
pen.Color = Color.Silver;
gc.DrawLine(pen, i, j0, i, j1); // y坐标轴
}
}
pen.Color = Color.Red;
for (i = i0; i <= i1; i++)
{
double x = x0 + (i - i0) * rx;
double y = fx.Compute(x);
if (double.IsInfinity(y) || double.IsNaN(y))
{
continue;
}
j = j1 - (int)((y - y0) / ry);
if (j > j1 || j < j0)
{
continue;
}
gc.DrawLine(pen, i, j, i + 1, j); // 画函数的图形
}
}
catch (Exception ex)
{
StringFormat f = new StringFormat();
f.LineAlignment = StringAlignment.Center;
f.Alignment = StringAlignment.Center;
gc.DrawString(ex.Message, new Font("Courier New", 10), Brushes.Blue, new Rectangle(5, fungraph_title_height, panel_fungraph.Width, panel_fungraph.Height), f);
fungraph_needrsdaw = false;
button31.Text = "绘制函数图像";
fungraph_dawing = false;
panel_fungraph.Invalidate();
return(false);
}
}
}
fungraph_needrsdaw = false;
}
button31.Text = "绘制函数图像";
fungraph_dawing = false;
panel_fungraph.Invalidate();
return(true);
}