FIXED: PathAway Map Manager colour depth problem

Questions and problems regarding PathAway Map Manager

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FIXED: PathAway Map Manager colour depth problem

Postby PD » Thu Aug 04, 2005 2:48 pm


I downloaded PathAway trial and I was trying to import a jpg satellite picture into Map Manager. I have the coordinates of the corners so I did a calibration and everything is ok. Of course, being a 2400 pixel image, the 16 bit colour representation occupies around 8MB of space, and it's not really needed, an 8 bit representation would be fine, so I tried to downsample the colour depth to 8 bit in Map Manager.

The problem arises here - changing from 16 bit to 8 bit basically destroys all detail in the map.

At first I thought it was the dithering algorithm in Map Manager so I used IrfanView (a freeware image viewer) to reduce the colour depth from the original 24 bit in the jpg to 8 bit. The picture was fine, with some dithering but perfect colourwise. I then tried to import it into Map Manager choosing 8 bit colour (since it already had no more than 256 colours, it shouldn't need to change the colours further). I obtained basically the same result - the colours were all changed and the map was unuseable.

Is this expected behaviour, meaning that maps that have more than 256 colours in the original photo will always have to be imported under 16 bit colour even if one can use external programs to sucessfully convert the photos to 8 bit colour ?

Thanks for any help,


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Joined: Sat May 28, 2005 12:45 pm

8Bit Import Bug

Postby zamzon » Mon Oct 03, 2005 4:18 pm

Dear Scott,

I found the very same, when importing 8Bit BMP files into Mapmanager 3.1. I will send you an example map and a picture showing the differences in two running MMs.

Please explain this behaviour and provide a workaround (except using 16 Bit, this will not fit even on my 4GB CF card).

Thank you.

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Joined: Sat May 28, 2005 12:45 pm

Postby zamzon » Mon Oct 03, 2005 4:44 pm

Dear Scott,

I tryed to import the 8Bit files with 16Bit and then change the color depth inside MM. This gives even worse results: Completely wrong colours. This is ununsabel IMHO.

Then I wondered what 'Resample Original' does. After reading the manual I would suggest to name the menu command: 'Reread Picture' or 'Reread Bitmap', cause this is, what it does.

Thank you.


Importing 4-bit palette maps

Postby mumon » Mon Oct 24, 2005 4:47 am

I definitely didn't understand too, then I found a phrase on Pathaway Map Manager manual:

If you choose a color depth such as 8-bit and 4-bit, then for optimal color conversion, you can use the PathAway color Palette in your image editor before generating your map. The color palette files are called PW4BitColor.pal, and PW8BitColor.pal, and are stored in the Map Manager installation folder (Usually “Program Files\PathAway GPS 3”).

and I got it.

For some reason, the 4 and 8 bit palettes are fixed; you can't use an optimized one.
So you have to tell your conversion program that you intend to use a specific palette, then apply it. If you import an already reduced colors map in Pathaway Map Manager, it will convert your original optimized palette in the built-in one, giving awful results: if you import from a true colors map, it will reduce colors in a fast but poor way, giving only slightly better results. You can do far better with a specific image manipulation program; in my case, I've tried with GIMP ( So I:
    Copied the .pal files from Pathaway directory to the the GIMP palette directory;
    Since GIMP cannot directly use the .pal files, I had to convert them (pretty straightforward, change extension from .pal to .gpl then, with text editor, change the first few lines by copying from another .gpl file);
    Open GIMP, load the map image, select image->mode->indexed
    Choose "Custom Palette"; scroll to PW4BitColor or PW8BitColor; disable "remove unused colors";
    Go! Then save image as .bmp
    Import as usual in Pathaway Map Manager. You will notice the image will be exactly as in image manipulation program, despite the result won't be as good as with an optimized palette.

I have no idea of why Pathaway cannot use the imported file's own palette; maybe it's for compatibility with low-colors devices; only the author can tell...

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Postby TheSnake » Mon Jun 12, 2006 8:00 pm

Any update on this problem anyone ?

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Joined: Thu Nov 24, 2005 3:16 pm

Re: PathAway Map Manager colour depth problem

Postby jpgrohn » Sat Oct 21, 2006 1:53 pm

PD wrote:Hi,

The problem arises here - changing from 16 bit to 8 bit basically destroys all detail in the map.


I make my maps this way. ( I think that this most easy way)

First I get my map images to .jpg or other form (.pdf/.bmp/.tiff)

Then I "print" them by using PDFCreator (open source) to 256 colour (8 bit) .png file.
Then I crop map with Ms Office Picture Manager if I need and save map to .png again.

After that I import map.png to Map Manager and calibrate it with 4 corners. (known points/wgs84)

Map resolution/size can change by selecting paper size letter/A4/A2 and selecting dpi's in PDFCreator.

PDFCreator "do well" colours converting to 8 bit.


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Postby Scott » Wed Apr 18, 2007 8:48 pm

We have made some significant improvements to the color conversion to 8-bit. Please try some of these maps again and let me know how they work for you.

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