Question: Image opacity, transprency and overlay

Dear all,

I encountered a problem to overlay the image produced by Maple.

I would like to overlay the image to google map.

The image should be opaque to let the user still can see the original google map.

However, i cannot find the function in Maple to set opacity for the output image. There is functions to set transparency, but it is not what I like to have.

Here is the code

with(plots):
interface(plotdevice):
plotsetup(gif, plotoutput = "d:\\2009.gif",plotoptions="transparent=true"):
Data := op(1, fscanf("d:\\datalist2009.txt", "%{500,270,3}fa")):
lseq := [seq([seq(Data[i, j, 3], j = 1 .. 270)], i = 1 .. 500)]:
a := listdensityplot(lseq, colorstyle = HUE, style = PATCHNOGRID, transparency = .4, axes = none):
b := listcontplot(lseq, axes = none):
display(a, b, scaling = constrained);
 

There are two questions:

1. If i set  plotoptions="transparent=true", the transparency setting in listdensityplot doesnt take effect. However, if i remove the 'plotoptions="transparent=true"', the images will look transprent (but not opaque, that means the image still cover the underlying google map)

2. If i execute the following code using "cmaple.exe" from command line,

with(plots):
interface(plotdevice):
plotsetup(gif, plotoutput = "d:\\2009.gif"):
Data := op(1, fscanf("d:\\datalist2009.txt", "%{500,270,3}fa")):
lseq := [seq([seq(Data[i, j, 3], j = 1 .. 270)], i = 1 .. 500)]:
a := listdensityplot(lseq, colorstyle = HUE, style = PATCHNOGRID, transparency = .4, axes = none):
b := listcontplot(lseq, axes = none):
display(a, b, scaling = constrained);

Even the transparency setting in listdensityplot doesnt work.

Can anyone help on this?