Alpha channel issue
andyeder
Global Mapper UserTrusted User
Hi Mike,
I was looking into ways by which I could create a halo around text labels such that, for example, dark text would stand out against dark backgrounds. My solution was to simply produce two maps:
The "text labels only" map was exported as a PNG (with Alpha channel) so that it could be loaded into Photoshop for editing - i.e. adding a halo effect to the labels. It was then used as an overlay over the "map data only" map. This worked well up to a point.
I noticed that when my maps were <= 1:50k I suddenly lost the Alpha channel when exporting the labels map. This was the case with both PNG and GeoTIFF formats (I didn't try any others). The "Make Background (Void) Pixels Transparent" was checked as it was for maps > 1:50k).
I'm using Global Mapper v11.02 (64-bit) on Windows 7 Ultimate (64-bit).
Regards,
Andy
I was looking into ways by which I could create a halo around text labels such that, for example, dark text would stand out against dark backgrounds. My solution was to simply produce two maps:
- Map data only
- Text labels only
The "text labels only" map was exported as a PNG (with Alpha channel) so that it could be loaded into Photoshop for editing - i.e. adding a halo effect to the labels. It was then used as an overlay over the "map data only" map. This worked well up to a point.
I noticed that when my maps were <= 1:50k I suddenly lost the Alpha channel when exporting the labels map. This was the case with both PNG and GeoTIFF formats (I didn't try any others). The "Make Background (Void) Pixels Transparent" was checked as it was for maps > 1:50k).
I'm using Global Mapper v11.02 (64-bit) on Windows 7 Ultimate (64-bit).
Regards,
Andy
Comments
-
Andy,
That is odd, can you post one of your PNG files that loses the alpha value or email it to support@globalmapper.com? If you load the files back into Global Mapper is the alpha not there either? I'm just wondering if maybe you hit some kind of size limit for alpha-images in Photoshop and the alpha is being ignored beyond that point.
Thanks,
Mike
Global Mapper Support
support@globalmapper.com -
global_mapper wrote: »That is odd, can you post one of your PNG files that loses the alpha value or email it to support@globalmapper.com? If you load the files back into Global Mapper is the alpha not there either? I'm just wondering if maybe you hit some kind of size limit for alpha-images in Photoshop and the alpha is being ignored beyond that point.
Mike,
If I immediately load the files back into Global Mapper I find that the alpha information has been lost. I will shortly e-mail you one of the exported files that has lost the alpha channel.
Many thanks,
Andy -
Andy,
I think that I found the issue. I have placed a new build at http://www.globalmapper.com/global_mapper11.zip with a potential fix for you to try. Simply download that file and extract the contents into your existing v11.xx installation folder to give it a try. If you are using the 64-bit v11 version there is a new build at http://www.globalmapper.com/global_mapper11_64bit.zip .
Let me know if I can be of further assistance.
Thanks,
Mike
Global Mapper Support
support@globalmapper.com -
Hi Mike,
I've just tried the new 64-bit executable build and I'm happy to report that all appears to be working well (at least with the GeoTiff's I'm currently exporting to).
Many thanks for your prompt replies and the rapid bug fix - very much appreciated.
Regards,
Andy
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