8.2.9 Using gradient fill for bar graphs

It is possible to use color gradient fill for the individual bars in the bar graph.

Color gradient fill fills a rectangle with a smooth transition between two colors. In what direction the transition goes (from left to right, down and up, from the middle and out etc) is determined by the style of the gradient fill. JpGraph currently supports 8 different styles. All supported styles are displayed in the figure below.

Figure 44: [src] 

Figure 45: [src] 

Figure 46: [src] 

Figure 47: [src] 

Figure 48: [src] 

Figure 49: [src] 

Figure 50: [src] 

Figure 51: [src] 

To specify a gradient fill for the bar plots you make use of the method BarPlot::SetFillGradient() . See the class reference for details of this function.

When using gradient fills there are a couple of caveats you should be aware of:

• gradient filling is computational expensive. Large plots with gradient fill will take in the order of 6 times longer to fill then for a normal one-color fill. This might to some extent be helped by making use of the cache feature of JpGraph so that the graph is only generated a few times.
• gradient filling will make use of much more colors (by definition) this will make the color palette for the image bigger and hence make the overall image larger. It might also have some severe effect on using anti-aliased line in the same image as color gradient filling since anti-aliased lines also have the possibility to make use of many colors. Hence the color palette might not be big enough for all the colors you need. So if you use gradient fills you should also be using a true-color image since you otherwise run out of colors.
  This problem is often seen as that for no apparent reason some color you have specified in the image does appear as another color. (This is not a bug in JpGraph!) This is something to especially watch out for when enabling anti-aliasing since that also uses a lot of colors. Since the numbers of colors used with anti-aliasing depends on the angle on the lines it is impossible to foresee the number of colors used for this.