SetPrintImage — Determine whether or not to automatically output the image when the plot is drawn
$plot->SetPrintImage($pi)
SetPrintImage determines whether or not to automatically
output the image (as if PrintImage was used) when a plot
is drawn (with DrawGraph). The default is True.
When putting multiple plots on one image, is is necessary to defer PrintImage
until after all the plots have been drawn.
$piTrue to automatically print the image when drawn with DrawGraph; False to defer printing the image until PrintImage is explicitly called.
To put multiple plots on an image, call SetPrintImage(False). Then for each plot activate the position for it with SetPlotAreaPixels, produce the plot, and draw it with DrawGraph. When all the plots are drawn, output the image with PrintImage.