Anti aliased lines not working for palette based images

Hi,

I am not able to draw the anti aliased lines for palette based images. I
followed the exact example given at this link:
http://www.libgd.org/Drawing#void_gdImageSetAntiAliased.28gdImagePtr_im.2C_int_c.29_.28FUNCTION.29

History of the problem I am facing:
Our site is serving palette based images (without anti aliasing) from long
time. We wanted to introduce true type fonts, I switched to true type image.
Also made the lines anti aliased. It increased the size of the image from
2KB to 8KB. If I use the palette based image for drawing true type fonts,
size gets reduced to 2.5KB but line is not getting anti aliased.

Also,  I tried saving the true type image as palette based image (indexed
based), though it reduced the size but reduction was just 1KB! Any thing I
am missing? I used the function gdImageTrueColorToPalette

Regards
Prashant