[prev in list] [next in list] [prev in thread] [next in thread] 

List:       imagemagick-user
Subject:    [magick-users] extract hexagonal regions with compose Src works
From:       Günter_Bachelier <guba () VI-ANEC ! de>
Date:       2008-08-14 9:32:52
Message-ID: 48A3FBC4.7090805 () VI-ANEC ! de
[Download RAW message or body]

Hello Anthony,

>   convert image1.png  image2.png \
>           mask.png -compose Src -composite \
>           result.png


First experiments are showing that with some minor adjustments
this seems to work: First I made a black background image for
image2 ($black) the same size as $extraction_mask (white hexagon
on black background) and

$img->Composite(image=>$black, mask=>$extraction_mask, compose=>'Src', 
gravity=>'Center'); 

delivers first the opposite from from what I want: extracted was the region
outside the white hexagon not inside. So I negate the $extraction_mask
(black hexagon on white background) and now the intended
region inside the hexagon is extracted.
Thank you very much for your help!!


Guenter






Anthony Thyssen schrieb:
> =?ISO-8859-1?Q?G=FCnter_Bachelier?= on  wrote...
> | Hello,
> |
> | I want to extract specific hexagonal regions with freestanding
> | structures from images (p3m1 tiles and patterns) like
> |
> | http://www.vi-anec.de/Trance-Art/IM-examples/p3m1_extraction/extraction_type_1.jpg
> | http://www.vi-anec.de/Trance-Art/IM-examples/p3m1_extraction/extraction_type_2.jpg
> |
> | I have tried to make this by drawing an extraction mask
> | (with matte=>'false') and use compose=>'CopyOpacity'
> | but the image remains unchanged after the operation.
> | See PerlMagick code in
> |
> | http://www.vi-anec.de/Trance-Art/IM-examples/p3m1_extraction/Test_p3m1_extraction.PLX
> |
> | I would appreciate any help because I need such an extraction
> | method also for some other symmetry group tiles and patterns.
> | Thank you very much!
> |
> |
> Sorry fro the late reply but I didn't think of an aswer until late last
> night.
>
> Are you trying to JUST extract the masked region, or will you overlay
> that extraction over another image!
>
> Either way the   3 imae Alpha Composite Masking should NOT have the
> alpha channel limitation of CopyOpacity, and can be used to either extract
> or blend two images.
>
>    convert image1.png  image2.png \
>            mask.png -compose Src -composite \
>            result.png
>
> This should do a bleaned overlay of image2.png (Src) with image1 (dest)
> according to the mask image.
>
> See Using a Mask to Limit Composed Area
>   http://www.imagemagick.org/Usage/compose/#mask
> Also see Masked Alpha Composition
>     http://www.imagemagick.org/Usage/channels/#masked_compose
>
> No alpha channel is needed for this thpe of operation.
>
> If one of the images (say images2.png) is an empty (null:) image
> and the -compose method is  'Clear'  then you can use the mask to
> 'clear' or make transparent areas of the first image (assuming it has
> an alpha channel).
>
> For example
>     convert image.png  null:  -compose Clear -composite  result.png
>
> The second image in this case does not matter at all, it is nor
> referenced by the 'Clear'  Duff-Porter composition method.
> However the first image MUST have an alpha/matte channel our you will
> get black instead of transparent.
>
> Ways of converting a greyscale mask image into a shaped mask image
> with transparency (for duff-porter style operations) is given in
>    http://www.imagemagick.org/Usage/channels/#shapes
>
> The simplest way is actually to -combine the gray-scale image using
> a   -channel A    the other color connels will then default to the
> background color, though that does not matter if you only plan to use a
> shape mask as a 'cookie cutter'.
>
> NOTE:  I would also read the   Dst_In and Dst_Out composition operators
> and how these to operators are designed so that you 'blend' or 'plus'
> (addition) the resulting images together to get a seamless result.
>
> See http://www.imagemagick.org/Usage/compose/#dstin
> which uses one cookie cutter image, to get the 'in' and 'out' parts
> of another image, then 'Plus' re-joins the images back into the original
> image.  An internal test of IM checks that this result is seamless.
>
> That is the alpha channel comes out to perfect opacity, no
> semi-transparency, or extra overlay (super-opacity), just as you would
> get for a perfect blend of two cookie-cut images.
>
>
>   Anthony Thyssen ( System Programmer )    <A.Thyssen@griffith.edu.au>
>  -----------------------------------------------------------------------------
> You're traveling through another dimension -- a dimension not only of sight and
> sound but of mind. A journey into a wonderous land whose boundaries are that of
> imagination.  That's a signpost up ahead: your next stop: the Twilight Zone!
>  -----------------------------------------------------------------------------
>      Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/
>
>   

_______________________________________________
Magick-users mailing list
Magick-users@imagemagick.org
http://studio.imagemagick.org/mailman/listinfo/magick-users
[prev in list] [next in list] [prev in thread] [next in thread]