L-VIS User Manual
83
LOYTEC
Version 6.2
LOYTEC electronics GmbH
line-art graphics, which contain large areas of uniform color. In such areas, dithering to the
exact color would not look as good as just picking one color from the VGA palette which is
closest to the intended color. If this is required, it is best to design the graphics using the
VGA palette and saving them in 256-color indexed format, like for example 8-bit BMP or
GIF. It is important to make sure that the palette used by the graphic tool is in fact the VGA
palette, otherwise the image will still need dithering.
8.7.4 Transparency
Transparency is handled in different ways, depending on the color mode of the project and
the properties of the image. In VGA projects, all images are displayed using VGA colors
only and transparency is defined by selecting a color index from the VGA palette. All
pixels using this color index are considered transparent if transparent background is turned
on. In true color projects, transparency is more complicated. Several cases exist:
The image contains transparency information (alpha channel data). In this case,
transparency is defined separately for each pixel in an additional set of data
embedded in the image file (the alpha channel). All pixels of the image will be
drawn according to their RGB color values from the main image data and the
opacity values from the alpha channel, independent of the
transparent
background
option.
The image does not contain any transparency information and uses colors which
are not part of the VGA color palette. In this case, all pixels are drawn fully
opaque, because there is no alpha channel data available and the specification of
a transparent color by VGA color index is not possible. This is the case for JPG
or BMP files and
also for resized VGA images
.
The image does not contain any transparency information, but uses only colors
from the VGA palette. In this case, transparency can be defined by VGA color
index in the same way as in VGA projects.
The LCD preview will show the image in the same way as the device, so the behavior of
transparency can be checked there. Also, pointing the mouse over an image in the image
manager will show a tool tip containing more information about the loaded image. In this
tool tip, it will be noted if the image contains alpha channel data and what the original
image format was.
8.7.5 Animations
Animation is supported via animated GIF and true color MNG files. MNG animations are
preprocessed by the configuration software when used in projects for VGA devices, such
that both formats may be used independent of the target device model. Note that for true
color devices, the MNG format is preferred as it avoids color dithering artifacts.
NOTE:
Keep in mind that playing animations can result in a significant use of both memory and
CPU time. Also, there is no special handling for animations which contain only one frame.
Use a still image file format like JPG or PNG for images which are not true animations.
8.7.6 Supported File Types
The following image file types are supported:
Bitmaps (*.bmp)
Icons (*.ico)
Joint Photographic Experts Group / JPEG (*.jpg)
Tagged Image File Format / TIFF (*.tif)
