Re: Creating PNG file with transparency

Hello,

2008/10/9 Bob Friesenhahn <[email protected]>

>
> While most graphics programs use an alpha channel which represents the
> degree of transparency, GraphicsMagich has an opacity channel which
> represents the degree of opacity (inverse of transparency).  An opaque image
> has an opacity value of 0 and a completely transparent pixel has an opacity
> value of MaxRGB.  In the "0, 0, 0,255", the 255 indicates completely
> transparent.  Similarly, the "FF" is max range in the color specification
> and indicates completely transparent.
>
> PNG and GIF have the ability to assign a single color as being the
> "transparent".  This requires a colormapped image representation.
> GraphicsMagick has a special "PNG8" output option to support this binary
> transparency.
>
Thanks for your explanation.


>
>
>  A sample code would be nice if you are kind enough.
>>
>
> While I will not write the entire program for you, causing an image color
> to be transparent is quite easy to do via the 'transparent' method of the
> Image class.  For example
>
>  image.transparent("white");

Is this equivalent to

image.matteColor("white");  // ?


>
> will set any white color in the image to transparent.  You can explicity
> write PNG8 format like
>
>  image.write("PNG8:output.png").

I write:

image.magick("PNG8");
image.write("output.png");

Are they the same?


>
> You can also create a transparent white canvas image and draw or composite
> on top of it, but this may obtain full alpha transparency rather than simple
> binary transparency.
>
>
Do you mean something like:

Image image( "400x400", "white" );
// write some pixels with
// image.pixelColor
image.write( "output.png" );

-- 
Best Regards,
Nguyen Hung Vu ( Nguyễn Vũ Hưng )
vuhung16plus{remove}@gmail.dot.com
<vuhung16plus%7Bremove%[email protected]>, YIM: vuhung16 , Skype:
vuhung16dg
A brief profile: http://www.hn.is.uec.ac.jp/~vuhung/Nguyen.Vu.Hung.html

-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/

_______________________________________________
Graphicsmagick-core mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/graphicsmagick-core