Alpha not working in Imager 0.99 [rt.cpan.org #97404]

[tonycoz]

Migrated from rt.cpan.org#97404 (status was 'open')

Requestors:

• jt@plainblack.com

Attachments:

• alpha-test.png
• alpha.pl

From jt@plainblack.com on 2014-07-22 15:40:15
:

I tried getting alpha transparencies working following the instructions here: http://imager.perl.org/docs/Imager/Color.html

However, no matter what I do, the alpha channel doesn�t seem to work. I may be doing something wrong, or it may be broken. I thought I should report it to find out.

I�ve attached some sample code and a sample output image.

From tonyc@cpan.org on 2014-07-24 13:21:44
:

On Tue Jul 22 11:40:15 2014, jt@plainblack.com wrote:
> I tried getting alpha transparencies working following the
> instructions here: http://imager.perl.org/docs/Imager/Color.html
> 
> However, no matter what I do, the alpha channel doesn�t seem to work.
> I may be doing something wrong, or it may be broken. I thought I
> should report it to find out.
> 
> I�ve attached some sample code and a sample output image.

It's more a missing feature.

By default, box(), and most other methods, replace the underlying pixel rather than combining with it.

If you sample had used a 4 channel image, the blue part of the image would have been translucent.

This is something I plan to change, someday, but there are other issues I want to fix first.

You can use fill objects (and Imager's shortcut for fill objects) to do transparent fills:

  $image->box(fill => { solid => $color, combine => "normal" },
              xmin => 150, ymin => 150, xmax => 250, ymax => 250)
      or die $image->errstr;

Note that setting "filled" to non-zero as you did causes the "fill" parameter to be ignored.

Tony