converting png to gif

[moneywasher]

When I convert png images with a white background ( as example: screenshots of webpages) to the gif format (256 colors) bcoz of it's lower filesize, than it's always ends with a dirty gray instead of a clean white background. So why XnView is not able to reproduce pure white gif images? White is beside of black, the main image in every little color system.

[xnview]

the png is 256colors?

[moneywasher]

no, of course not. The png's are full color images (32bit ... I guess) from a screenshot program for taken copies of webpages.
You mean, the png's should be converted from 32bit to 8bit (256 colors), before to save them as gif's?
Okay, I will try it.

[moneywasher]

Ok, I tried and it works. It shows a clean white color on the gif images. ... but the converting of a png from 32 to 8bit is mega slowly, when the png image is as example, some MB by filesize. And it uses a lot of my CPU in this long wait.