How to do redusing color and alpha for PNG RGBA32bit to RGBA

[yush125]

Here is document and sample about redusing color RGBA32bit color to RGBA8bit with high quality.
http://www.webtech.co.jp/imesta/psp/f_alpha_blend.html

Here is sample picture.


And this is my command and result picture "orijinal_after.png"

Code: Select all

convert "orijinal.png" -ordered-dither o8x8,8,8,8 "orijinal_after.png"

Result of 32bit to 8bit color with using IM.

It has bit more noisy than Optpix imesta's one.

If you know more better option , tell me about that.

[fmw42]

You are dithering which will add the dither pattern. I suspect that is not what you want to do.

try

convert image.png PNG8:result.png

[glennrp]

You are dithering which will add the dither pattern. I suspect that is not what you want to do.

try

convert image.png PNG8:result.png

PNG8 does quick-and-dirty color reduction and will produce severe banding.

Code: Select all

convert image.png -colors 255 result.png

will do better. Or, if you want a 1-bit alpha channel, use png8: after reducing
the colors:

Code: Select all

convert image.png -colors 255 png8:result.png

[anthony]

The ordered dither only provides a uniform colormap. As a consequence no all colors in that map is being used for that image.

You can increase the color counts until you get about 255 colors in the reulting image.
An example of doing this is in Video to GIF animation
http://www.imagemagick.org/Usage/video/#gif

Look for "Higher Quality Ordered Dithered Video"

[yush125]

Hi,everyone.

fmw42,glennrp,anthony Thank you for answering.

That's a very helpful for me.

And I did as following your advice.
Here is result.It's quite better than my first.Almost I satisfied with that.



Thank you very much.

yush125