Creating
Handheld PC Wallpaper in Adobe Photoshop
| H/PC Colour Tables |
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| HPC Factor |
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CESD-S-0022Applies To:
- Windows CE for Handheld PC
Overview:
Following on from our last Wallpapers How-to (CESD-S-0013), which
covered how to create 2BP files for your Windows CE device. This
article covers how to create Wallpapers for a Handheld PC device
in Adobe Photoshop, as BitMap files, rendered specifically for the
display colour / shade depth that you are using.
This article is intended for creating .bmp files for use on the
Handheld PC. Allowing for more customisation than that provided
by the 2BP engine of Tascal Soft's bmp2bp. This article does not
allow for the saving of files with the .2bp compression suffix -
Please see CESD-S-0013 if you wish to render
.2bp files
This article makes provisions for 4 & 16 Shade Grey Scale devices,
as well as 16 and 256 colour devices. High Colour devices do not
benefit visually from rendering the image to a smaller colour palette.
This article is primarily based around the CESD-S-0022 File Colour
Tables file download.
How-to Guide:
The following how-to steps describe how to render
an image using a smaller Colour Palette in order to reduce the file
size of a BitMap graphic and customise its rendered appearance on
your device. It assumes that the user is familiar with Adobe Photoshop.
NB: For the benefit of non Photoshop users. Windows
Colour Palette files (.pal) are provided in the download as well
as Adobe Colour Table (.act) files. Other imaging applications may
be able to modify their output using either file.
This process has been written for Adobe Photoshop on the PC. It will be similar
for Photoshop on the Mac when importing the Act palettes.
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Extract the ACT files from the hpcf-hpc-col-tables.zip to
your hard drive and Launch Adobe Photoshop.
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Import the image you wish to convert:
If the Image is to become a desktop wallpaper
ensure that the images maximum size meets the screen size
of your device. The diagram below shows the necessary image
specification.
Full VGA:
640 x 454 + 26
Half VGA (Clam Shell):
640 x 214 + 26
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In order to manipulate the image into the
desired depth of colour you must change the Image Mode from
a True Colour image (usually RGB). To a image which uses a
mapped colour palette or Indexed Colour.
To begin the process of converting the image to Index Colour:
- Open the 'Image' menu
- Expand the 'Mode' option and Select 'Indexed Color...
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The Indexed Color configuration Window:
Indexed Colour allows you to specify up to 256 unique colours
for an image to be displayed in. One of which can be a transparency.
The reason for having indexed colour graphics is to reduce
the file size of a graphic, while retaining the overall image
quality for viewing on a low colour depth display.
Early PC's often up until 1995 and Handheld PC's up until Handheld PC
Professional was released. Did not have the ability to display High Colour
graphics, so using High or True Colour (16, 24 and 32 bit) graphics on
these devices is a waste of storage space.
Firstly you need to select the Colour Palette
that you wish to convert the image into.
From the 'Palette' drop box choose 'Custom...'
to open the Colour Table window.
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In the Colour Table window choose the 'Load...' button.
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Navigate to the location where you extracted the CESD-S-0022
Adobe Colour Tables.
Select the appropriate Colour Table for your device. For example the
HP 320lx has a 4 Shades Grey Scale display, so select the appropriate
profile for your target screen.
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Photoshop will load the profile, in the example the 16 Colour
profile has been loaded.
Index Colour profiles allow for a maximum of 256 colours,
which will be displayed in the 16 x 16 grid displayed below.
Click the 'OK' button to apply the profile to
the image
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As you can see, the example image has changed considerably.
Photoshop returns you to the Indexed Colour
screen to allow you to further configure the display options
of your image.
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The main configurable option here is the 'Dither'
drop box
Cycle between the 4 Dither options in the list. None, Diffusion,
Pattern and Noise. Each one produces a different variant of your image.
Depending on the complexity of the original image, different dither modes
will produce a different result.
The Diffusion option also allows further customisation
by selecting how heavy, as a percentage the dither is.
As a general rule, for photographic images,
the diffusion option produces the best results.
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Displayed below are renders of our example image in each
of the different dither formats.
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| Dither: None |
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| Dither: Diffusion |
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| Dither: Pattern |
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| Dither: Noise |
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Demonstration Image © BBC,
Snell & Wilcox
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Links:
Adobe Systems: http://www.adobe.com/
Snell & Wilcox Home Page: http://www.snellwilcox.com/internet/
BBC Home Page: http://www.bbc.co.uk/
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