[magick-users] Fw: -compose

[Anthony Thyssen]

On Fri, 26 Dec 2008 23:11:32 -0800
magick-users-bounces at imagemagick.org wrote:

| So I was doing a book layout, putting small pages on a big page.
| 
| The idea is that page fragments, formatted to fit small page sizes 
| already, or easily cropped from something containing it, would be placed 
| in various spots on the big page.
| 
| Some pages are to be composed of multiple pages.  Note c004.tif and 
| c005.tif below... they are both contributing to the same small page, but 
| do not both contain black stuff at the same places.
| 
| All is bitonal black and white, so it seems like -compose multiply would 
| let one merge these various pages, and it seems to work in some smaller 
| cases I had done, where I build all the pages separately and merge them, 
| but then that took lots of memory, so I thought I'd -flatten as I go.... 
| but then c004.tif doesn't get included... apparently it gets overlaid by 
| c005.tif, even the white parts.
| 
| Does -compose only persist for one -flatten?  I thought as a setting, it 
| would persist until it was changed.
| 
The problem is that -compose is for some file formats a image meta-data
setting, as so reading an image overrides the existing setting.

I myself have had problems with this, and I think these problem will persist
until Image magick as a formal (internal) notion of a 'global' override
verses the image meta-data value.

My own thinking is that global values should override any and all meta-data
values unless left unset or the user purposefully unsets the global override
using +value.

Similarly if the user wants to specifically set the image meta data value the
-set operator should be used.

However IM has no true notion of a global override, verses image meta-data.
Compose in particular is only seen by the alpha composition operator simply as
image meta-data.

Until the library is changed to a data-structure that consists of
an 'image'  with pointers to 'image-meta-data' and 'global-overrides',
with library routines to get the appropriate settings. I doubt the confusion
will have any resolution anytime soon.



  Anthony Thyssen ( System Programmer )    <A.Thyssen at griffith.edu.au>
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  Error reading from device Brain - (A)bort, (R)etry, (G)et a coke?
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     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/



  Anthony Thyssen ( System Programmer )    <A.Thyssen at griffith.edu.au>
 -----------------------------------------------------------------------------
  Losing one glove is certainly painful, but nothing compared to the pain,
  of losing one, throwing away the other, and finding the first one again.
                                                             -- Piet Hein
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     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/