Graph report for netcf Development

Drawing graphical reports

You can also use the. NET Compact Framework rendering function to draw graphical reports, such as pie charts, column charts, or line charts. The following uses a pie chart as an example to describe how to create a pie chart. The code for creating a pie chart is shown in listing 7-8.

 

Listing 7-8: creating a pie chart

...... Dim CBMP as new Bitmap (236,184) 'create a bitmap instance with a canvas width of 236 and a height of 184 Dim cgraphic as graphics Dim ccolor () as color = {color. Red, color. Blue, color. Green, color. Gray ,_ Color. lightcoral, color. Gold} '5 colors Dim cpen as pen Dim csolidbrush as solidbrush Dim cpoints () as point Dim rownum as integer = 3' defines the number of slice Blocks Dim I as integer = 0 Dim J as integer = 0 Dim cangle as integer = 0 Dim TMP as integer = 0 Dim xcirclecenter as integer = 100 'defines the center X coordinate Dim ycirclecenter as integer = 100 'defines the Y coordinate of the center Cgraphic = graphics. fromimage (CBMP) Cgraphic. Clear (color. Snow) For J = 0 to rownum Cangle = 90' defines the slice Angle Redim cpoints (cangle + 1) 'Draw circles with mathematical formulas Cpen = new pen (ccolor (J), 3) Csolidbrush = new solidbrush (ccolor (j )) For I = TMP to TMP + cangle Cpoints (I-TMP) = new point Cpoints (I-TMP). x = (1-system. Math. Sin (I/360*2 * system. Math. Pi) * (xcirclecenter-30) + 10 Cpoints (I-TMP). Y = (1-system. Math. Cos (I/360*2 * system. Math. Pi) * (ycirclecenter-30) + 10 Next I 'Add the coordinate point of the center Cpoints (cangle + 1) = new point Cpoints (cangle + 1). x = xcirclecenter-20 Cpoints (cangle + 1). Y = ycirclecenter-20 'Area of the slice to be drawn Cpen = new pen (ccolor (J), 3) Csolidbrush = new solidbrush (ccolor (j )) Cgraphic. drawpolygon (cpen, cpoints) Cgraphic. fillpolygon (csolidbrush, cpoints) TMP = TMP + cangle Next Pb_graphic.image = CBMP ......

 

In listing 7-8, a canvas of the specified size is first defined, and the canvas is also a bitmap instance. Then define the coordinates of the center. To determine the coordinates of the center point, you can use the calculation formula to obtain a set of points that constitute the arc of each slice. The set of arc points and the center point form a closed sector area. After determining the slice area, you can start to draw a slice chart and fill the slice area with different colors. Finally, the drawn bitmap instance is displayed through the picturebox control. The execution result of listing 7-8 is 7-6.

 

Figure 7-6: Pie Chart

With the same principle, you can also implement a bar chart, as shown in 7-7.

Figure 7-7: bar chart