1. Palette Problem
Hi All!
I've a little problem using palette in Eu using Read_bitmpap() : How
to Change a palette of a Bmp ? :
I want to use only one palette but my Bmps don't have the same pal, And I
don't know how to display 2 Bmp with differents pals at the same time on
Screen. Can you help me a bit please ?
Gwen
2. Re: Palette Problem
> I've a little problem using palette in Eu using Read_bitmpap() : How
> to Change a palette of a Bmp ? :
> I want to use only one palette but my Bmps don't have the same pal, And I
> don't know how to display 2 Bmp with differents pals at the same time on
> Screen. Can you help me a bit please ?
There are a number of possible 'solutions' .. I'll list them all:
* Match the associated rgb-value (in the palette) of pic 1 with those found
in pic 2 and change the color-index-values in
one the two pictures accordingly.
* Use a true-color video mode
* Download paintbrush pro or some other image program and have it match the
palettes for you
* Use a good graphics library that matches such indexes for you.
The first can be done using any of the few libraries available for this. (I
can remember one by Lucius Hilley, am not sure
though)
The second can be done by Neil (Pete's), and in theory you _could_ use
TrueEU (Hawke's / Christopher-Street). (but then
again, I can also go around jumping around in my room with a shoe in my mouth
.. 
.. yet I suggest Neil anyway.
The third: go to http://www.jasc.com
The fourth: Neil again. (when in an palette mode, it matches new loaded
pictures with the current palette automatically)
Ralf N.
3. Re: Palette Problem
Message text written by Gwen:
>I've a little problem using palette in Eu using Read_bitmpap() : How
to Change a palette of a Bmp ? :
I want to use only one palette but my Bmps don't have the same pal, And I=
don't know how to display 2 Bmp with differents pals at the same time on
Screen. Can you help me a bit please ?<
Only one palette can be active, so if you try to show two images with
different palettes at the same time, the colors of one will be wrong. Th=
e
easiest solution is to convert one image to the palette of the other. I
wrote some palette utilities for just this purpose, which are posted on t=
he
RDS web page (recent contributions). HTH.
Colin
4. Re: Palette Problem
Hello Colin:
This is Lucius, Remapping palettes does work great MOST of the time but
after working with several images I have found several problems with it.
1. If it does work and work well you would want to save a copy of the image
with the new palette. Remapping on the fly is a little slow.
2. 1 reason it may not work is that you have an image that has abundance of
1 color in the palette. Example: an image of Lava would have a palette
consumed with different shades of red. And an image of the sky would
have many blues. These 2 images won't simply remap very well from their
palette to the others palette. You may have to Build a new palette that
is a partial mixture of the 2 and remap both images to it.
3. I doubt Colin took this into account but I may be wrong. I know I took
it into account when writing my rountines and gave up before solving
the problem of drastically different palettes. I think Pete Eberlein
wrote some excellent routines in this area. NOT SURE.
Lucius L. Hilley III
On Thu, 13 May 1999 10:24:43 -0400, Colin Taylor <cetaylor at COMPUSERVE.COM>
wrote:
>Message text written by Gwen:
>>I've a little problem using palette in Eu using Read_bitmpap() : How
>to Change a palette of a Bmp ? :
>I want to use only one palette but my Bmps don't have the same pal, And I
>don't know how to display 2 Bmp with differents pals at the same time on
>Screen. Can you help me a bit please ?<
>
>Only one palette can be active, so if you try to show two images with
>different palettes at the same time, the colors of one will be wrong. The
>easiest solution is to convert one image to the palette of the other. I
>wrote some palette utilities for just this purpose, which are posted on the
>RDS web page (recent contributions). HTH.
>
>Colin
5. Re: Palette Problem
Gwenakl Joret wrote:
>I've a little problem using palette in Eu using Read_bitmpap() : How
>to Change a palette of a Bmp ? :
The routine readBitmapFromFile() returns the bitmap portion (or an error
code) of the requested bitmap. It reads the requested bitmap, then maps the
bitmap's palette to the current palette. Finally, it replaces the references
in the bitmap from it's original pal to the current pal.
Some obvious points:
1. You need to set the graphics_mode before calling the function.
2. Resolutions with more colors take longer to convert
3. It works in all graphics modes, but higher modes have more colors, so map
better
To speed things up, I can suggest the following:
1. Pete has an assembly version of this on his home page - runs faster!
2. Reduce the colors in the bitmap you are reading, if you can.
3. If you always use the same bitmaps, map them all to the same palette:
- read all the bitmaps mapped to the same palette
- save the bitmaps with the new palette
Once they are converted over, you can use the regular Euphoria tools
again.
Hope this helps!
-- David Cuny
include image.e
procedure abortErr( sequence msg, sequence args )
-- display an error message and abort
printf( 1, msg, args )
abort( 0 )
end procedure
function abs( atom a )
-- return absolute value
if a > 0 then
return a
else
return -a
end if
end function
function convertToPalette( sequence sourcePal )
-- convert the color list to palette indexes
atom err, diff, best
sequence destPal, colorIndex
-- get palette
destPal = get_all_palette()
-- adjust source
sourcePal = floor( sourcePal/4 )
-- build holder for results
colorIndex = repeat( 0, length( sourcePal ) )
-- look at each entry
for i = 1 to length( sourcePal ) do
-- set the last best match as impossibly bad
best = #FFFFFF
-- look through the palette
for entry = 1 to length( destPal ) do
-- error amount for this entry
err = 0
-- for each {rgb}
for rgb = 1 to 3 do
-- error is difference between the two
diff = abs( sourcePal[i][rgb] - destPal[entry][rgb] )
err = err + diff
end for
-- better match than prior best match?
if err < best then
-- save error amount
best = err
-- store the palette index
colorIndex[i] = entry
end if
end for
end for
return colorIndex
end function
function readBitmapFromFile( sequence fName )
-- load a bitmap from the current file, and map to current palette
integer index
sequence replace
object res
-- attempt to read bitmap
res = read_bitmap( fName )
if integer( res ) then
-- return the error message
return res
end if
-- adjust the current palette
replace = convertToPalette(res[1])
-- replace values with references to new palette
for i = 1 to length( res[2] ) do
for j = 1 to length( res[2][i] ) do
-- get index
index = res[2][i][j]
-- get actual color
index = replace[index+1]-1
-- replace
res[2][i][j] = index
end for
end for
-- return bitmap
return res[2]
end function
6. Re: Palette Problem
Message text written by Lucius:
>Hello Colin:
This is Lucius, Remapping palettes does work great MOST of the time bu=
t
after working with several images I have found several problems with it.
1. If it does work and work well you would want to save a copy of the ima=
ge
with the new palette. Remapping on the fly is a little slow.
2. 1 reason it may not work is that you have an image that has abundance =
of
1 color in the palette. Example: an image of Lava would have a palette=
consumed with different shades of red. And an image of the sky would
have many blues. These 2 images won't simply remap very well from the=
ir
palette to the others palette. You may have to Build a new palette th=
at
is a partial mixture of the 2 and remap both images to it.
3. I doubt Colin took this into account but I may be wrong. I know I too=
k
it into account when writing my rountines and gave up before solving
the problem of drastically different palettes. I think Pete Eberlein
wrote some excellent routines in this area. NOT SURE.
Lucius L. Hilley III
<
If the palettes are very different, both images can be remapped to a comm=
on
palette such as a windoze or web palette or even a mac palette. Remappin=
g
on the fly is very fast for small images. For better-looking results, th=
e
images can be dithered to a new palette which is also fairly fast (usuall=
y
less tha 1 second for a 320x240 image on my machine).
Colin
7. Re: Palette Problem
Hi all
I tried a lot of functions to remap a palette, it works quite well !
Thanx for your help !
(Unfortunaly I need among other things to remap a clouds pic --> palette is
almost blue 
Gwen
