>I am having a problem with some bitmaps. I am not sure why, but since
>we have upgraded to MI 5.0 we get a white background on some images. The
>odd thing is that even if I set it to transparent, it will not be
>transparent. Some others will still change to transparent....is there a
>reasonable explanation for this?
After looking at the bitmaps Glen was kind enough to send us, and checking
with our developers, I have the dubious honor of reporting that yes, we
did introduce a bug in transparent raster image handling with MI Pro 5.0
Here's the situation:
1. MI Pro has supported transparency only in 8-bit color mode to date.
2. MI Pro uses a 256 color palette to display raster images in 8-bit
color.
3. MI Pro, before 5.0, kept track of the index of the transparent
color, not the transparent color itself.
4. To support surface thematic grids, MI Pro 5.0 stores the actual
transparent color value.
5. When MI Pro 5.0 prepares to draw a raster image with transparency,
still in 8-bit color only, it converts that color value back into
a palette index by searching the palette.
6. Unfortunately, MI Pro can find the wrong index if that color is
in the palette more than once. This can happen, for example, if
the image does not require all 256 possible entries and the rest
of the palette is filled with some default color.
7. The known work-arounds include:
a. use a 3rd-party tool to edit the image and change the color
of the pixels in the region that needs to be transparent to
another color that is not already in the palette.
b. use a 3rd-party tool that supports editing the palette
directly, and make sure that the color of the pixels in the
region that needs to be transparent is listed in the palette
only once.
>We have run into the same exact issue, and came to the
>conclusion that MapInfo rewrote the translator between 4.5 and 5.0 for
>.wmfs and .bmps and now does not handle the translation/saving process
>the same way. Additionally, the size of the file will be significantly
>different between the two (MUCH bigger). We're waiting on a "bug fix"
>for this, but in the meantime have resorted to running the workspace
>back through a version of 4.5 to convert.
Cindy, this sounds like a different issue. We did upgrade the 3rd-party
library in 5.0 that MI Pro uses for writing out images. We also now
default the image size to the size of the layout page instead of the
size of the layout window. Besides the size of the files, what else is
coming out differently?
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