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Re: How can I output a colored or gray raster image without deleting the existing content?

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markus.mail@kdwelt.de wrote:

> Hello,
> 
> I want to display a raster image on a specified area but the existing
> drawing in this area should be preserved (as much as it possible and makes
> sense).
> 
> With monochrome images this is no problem if you use "imagemask" (not
> "image"). Look at PLRM 4.10.6 (Masks): "Any portion of an image, whether
> black, white, color, or gray, completely obscures any marks that
> previously existed in the same place on the page. There is a special
> variant of a binary image, called a mask, whose properties are quite
> different. Whereas an image is opaque, a mask is partially transparent.
> The imagemask operator applies masks."
> 
> How can I do the same with "colorimage"? Analogous with above paragraph it
> would be something like "colorimagemask". Unfortunately this operator
> seems not to be available.
> 
> Any hints?
> 
> [P.S. On Postscript, imagemask is a somewhat special operator. It includes
> [both what to draw _and_ where to draw. On X11/GTK this is defined
> [separately: GDK_GC_SET_CLIP_MASK defines where to draw and
> [GDK_DRAW_GRAY_IMAGE or GDK_DRAW_RGB_IMAGE define what to draw. For
> [monochrome images you use GDK_DRAW_RECTANGLE after setting a color. This
> ["fills" the image area, but effects only places where the clipping mask
> [is true.]
> 
> Markus

In language level 3, this can be achieved by using 
a) the dictionary form of the image operator
and
b) using a type3 of type4 image dictionary

For the details see the PLRM (3rd ed.), section 4.10.6: Masked Images

Helge

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How can I output a colored or gray raster image without deleting the existing content? markus.mail@kdwelt.de - 2012-08-23 13:05 -0700
  Re: How can I output a colored or gray raster image without deleting the existing content? Helge Blischke <h.blischke@acm.org> - 2012-08-23 22:38 +0200
  Re: How can I output a colored or gray raster image without deleting the existing content? luser- -droog <mijoryx@yahoo.com> - 2012-08-23 19:29 -0700
    Re: How can I output a colored or gray raster image without deleting the existing content? markus.mail@kdwelt.de - 2012-08-24 10:46 -0700

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