Working With Palettes and Colors
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TPDesign4 Touch Panel Design Program
Working with Transparent Backgrounds
When you are applying an icon to a button, chances are that you will want to take advantage of
TPDesign4's ability to handle transparencies in bitmaps. Typically, transparency in bitmaps is used
for the background color, to accommodate layering of bitmap images without trying to match
colors across layers.
Bitmap images are always created in the shape of a rectangle, because they are raster images.
However, by assigning "transparent" as the background color, you can effectively change the shape
of the image. For example, if you have a button with a bitmap image (FIG. 29),
and you apply an icon that doesn't use transparent as the background color, you'll wind up with
something like this (FIG. 30):
Obviously you don't want that unsightly box framing the icon! You need to edit the icon's fill color
and make the background color transparent. With a transparent background color, the icon actually
retains its original rectangular shape, but will display without the background (FIG. 31):
Check the documentation for your image-editing program to learn about applying transparency to
your bitmaps. Generally speaking, you will apply a fill to the areas that you want to appear
transparent (in most cases the background), and select transparent as the fill color, just like you
would for any other color in the palette.
When using bitmaps with transparencies in TPDesign4, there are a few key concepts to understand:
 Of all the image file formats supported by TPDesign4, only one accommodates
transparency as a color: PNGs.
FIG. 29 A button with a bitmap image
FIG. 30 An icon that doesn't use transparent as the background color
FIG. 31 Icon with a transparent background color
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