Re: about platte

I use sample() in C++ code to make 'resize' instead of scale(), and the
result is much better, so
I think it's the algorithm of 'resize' that effects the result.

As you have mentioned, I tried different dither but it didn''t work.

2009/10/28 Anthony Thyssen <[email protected]>

> On Tue, 27 Oct 2009 19:44:42 +0800
> ZHOU Xiao-bo <[email protected]> wrote:
>
> | hi:
> |
> |     I found that when I resize and quantize a gif such as
> |
> |                  "http://img1.cache.netease.com/img09/logo/logo.gif"
> |
> |     using "convert logo.gif -resize 160x46 -colors 16 out.gif", I got a
> |     gif with bad quality.
> |
> |      But if I use "convert logo.gif -resize 160x46 tmp,gif"; and then
> |      "convert tmp.gif -colors 16 out.gif", the quality is much better.
> |
> |       I think it's because the platte has been changed when resizing.
> |       I found that platte of 'tmp.gif'  is much larger than that of
> | logo.gif.
> |       So, how can I get the better output image in c++ code?
> |        thanks a lot.
> |                                     ZHOU Xiaobo
> |
> Resize does not change the palette, it destroys the palette as it generate
> completely new colors as part of the process.
>
> The save to gif however restricted the colors to a new 256 color palette
> as part of the save.  This may be the cause of the improved result
>
> You could try the equivalent of
>   convert logo.gif -resize 160x46 -colors 256 -colors 16 out.gif
>
> Also you may like to try using a different dither,
>   -dither FloydSteinberg
> which may produce a better result for small images.
>
>
>  Anthony Thyssen ( System Programmer )    <[email protected]>
>
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