Add support for making the image background transparent

[cjfields]

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Author Name: Nathan S. (Nathan S.)
Original Redmine Issue: 2365, https://redmine.open-bio.org/issues/2365
Original Date: 2007-09-13
Original Assignee: Lincoln Stein

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It would be nice to be able to make the background of the image transparent if required.

[cjfields]

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Original Redmine Comment
Author Name: Nathan S.
Original Date: 2007-09-13T07:57:05Z

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Adding the following method to Bio::Graphics::Panel

sub make_bgcolor_transparent {
my $self = shift;
my $gd = $self->gd;

$gd->transparent($self->bgcolor);
}

allows one to say something like:
my $panel = Bio::Graphics::Panel->new(
-length => 5000,
-width => 1000
-pad_left => 10,
-pad_right => 100,
-key_style => ‘between’, # between, bottom, left, right, none
-bgcolor => ‘pink’,
);
$panel->make_bgcolor_transparent;
print $panel->png;

This has the effect of turning the default bgcolor of the panel (white) in the whole image to be transparent - so beware of any glyphs you want to actually contain white. If this is the case, you should set the bgcolor of the panel to something obscure that you don’t want to use in any of the glyphs, such that when $panel->make_bgcolor_transparent() is called, only the obscure coloured background is made transparent in the image.

[cjfields]

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Original Redmine Comment
Author Name: Chris Fields
Original Date: 2007-09-24T13:32:47Z

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As mentioned on the mail list:

http://article.gmane.org/gmane.comp.lang.perl.bio.general/15904/match=graphics+transparency

there could be issues with SVG output and transparency, so if transparency is added as an option this should be probably be addressed in some way.

[cjfields]

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Original Redmine Comment
Author Name: Lincoln Stein
Original Date: 2007-09-24T14:30:49Z

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This sounds like a good enhancement and I’ll try to write support for it in a way that doesn’t cause bad side effects.

-Lincoln

[cjfields]

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Original Redmine Comment
Author Name: Chris Fields
Original Date: 2008-11-21T00:46:00Z

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Not sure how far along this one is. Nathan, any word?

[cjfields]

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Original Redmine Comment
Author Name: Nathan S.
Original Date: 2008-11-23T21:27:55Z

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(In reply to comment #4)

Not sure how far along this one is. Nathan, any word?

Sorry, I’ve been away from Bioperl for a while and I haven’t used this since my original post - however, the new subroutine (make_bgcolor_transparent) I suggested should still work and probably just needs to be implemented. Obviously, if you set the background colour to be transparent, you need to be sure that the rest of the graphic doesn’t contain that colour - otherwise it will be made transparent also.

Nath

[cjfields]

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Original Redmine Comment
Author Name: Chris Fields
Original Date: 2008-12-16T00:41:52Z

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Seems to have stalled. Pushing to 1.6.x; may be worth moving this and other related Bio::Graphics bugs to Lincoln’s Sourceforge bug database, since Bio::Graphics is now a separate CPAN release.

[cjfields]

Migrated from OBF Redmine.