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[svg-developers] access to data underlying feDisplacementMap?

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  • ddailey
    Is it possible to read pixel values (RGBA) in SVG? The feDisplacementMap filter primitive does something very cool which is to use the pixel values from
    Message 1 of 5 , Aug 1 7:09 AM
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      Is it possible to read pixel values (RGBA) in SVG? The feDisplacementMap
      filter "primitive" does something very cool which is to use the pixel values
      from image A to distort image B. Hence at some lower level those pixel
      values are made accessible to SVG so that the filter primitive might do its
      work. I'm thinking of something like the getTotalLength and getPointAtLength
      methods associated with Bezier curves in the <path> object -- those loci
      need to be known anyhow for the browser to be able to render the path, so
      why not let them be obtainable by the SVG developer? (Just for fun I applied
      a displacement map to a path and then interrogated its points after it had
      been distorted, but so far as SVG seemed to know, its coordinates were still
      the same).
    • Andreas Neumann
      Hi, getting color values at a given pixel position is currently not possible. We are discussing this for SVG version 1.2 full as there are already many use
      Message 2 of 5 , Aug 1 8:55 AM
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        Hi,

        getting color values at a given pixel position is currently not possible.

        We are discussing this for SVG version 1.2 full as there are already many use cases. Its not
        in the upcoming SVG tiny spec, though.

        Andreas

        --- In svg-developers@yahoogroups.com, "ddailey" <ddailey@...> wrote:
        >
        > Is it possible to read pixel values (RGBA) in SVG? The feDisplacementMap
        > filter "primitive" does something very cool which is to use the pixel values
        > from image A to distort image B. Hence at some lower level those pixel
        > values are made accessible to SVG so that the filter primitive might do its
        > work. I'm thinking of something like the getTotalLength and getPointAtLength
        > methods associated with Bezier curves in the <path> object -- those loci
        > need to be known anyhow for the browser to be able to render the path, so
        > why not let them be obtainable by the SVG developer? (Just for fun I applied
        > a displacement map to a path and then interrogated its points after it had
        > been distorted, but so far as SVG seemed to know, its coordinates were still
        > the same).
        >
      • ddailey
        ... Thanks for the info Andreas. regards, David
        Message 3 of 5 , Aug 1 12:23 PM
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          > Hi,
          >
          > getting color values at a given pixel position is currently not possible.
          >
          > We are discussing this for SVG version 1.2 full as there are already many
          > use cases. Its not
          > in the upcoming SVG tiny spec, though.
          >
          > Andreas

          Thanks for the info Andreas.

          regards,
          David
        • Christophe Strobbe
          Hi Andreas, ... Do you have a pointer for this (a use case or a requirement)? I can t seem to find this in http://www.w3.org/TR/SVG2Reqs/ or
          Message 4 of 5 , Aug 2 7:38 AM
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            Hi Andreas,

            At 17:55 1/08/2006, Andreas wrote:

            >Hi,
            >
            >getting color values at a given pixel position is currently not possible.
            >
            >We are discussing this for SVG version 1.2 full as there are already many
            >use cases. Its not
            >in the upcoming SVG tiny spec, though.

            Do you have a pointer for this (a use case or a requirement)? I can't seem
            to find this in http://www.w3.org/TR/SVG2Reqs/ or
            http://www.w3.org/TR/2004/WD-SVG12-20041027/.

            Regards,

            Christophe


            --
            Christophe Strobbe
            K.U.Leuven - Departement of Electrical Engineering - Research Group on
            Document Architectures
            Kasteelpark Arenberg 10 - 3001 Leuven-Heverlee - BELGIUM
            tel: +32 16 32 85 51
            http://www.docarch.be/


            Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
          • Andreas Neumann
            ... already many ... can t seem ... Hi Christophe, here is one: http://www.w3.org/TR/2004/WD-SVG12-20041027/dom.html the getPixel() method on an SVGImage. I
            Message 5 of 5 , Aug 2 8:08 AM
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              > >We are discussing this for SVG version 1.2 full as there are
              already many
              > >use cases. Its not
              > >in the upcoming SVG tiny spec, though.
              >
              > Do you have a pointer for this (a use case or a requirement)? I
              can't seem
              > to find this in http://www.w3.org/TR/SVG2Reqs/ or
              > http://www.w3.org/TR/2004/WD-SVG12-20041027/.

              Hi Christophe,

              here is one:
              http://www.w3.org/TR/2004/WD-SVG12-20041027/dom.html

              the getPixel() method on an SVGImage.

              I haven't investigated that in detail though, what it actually does.

              Once the WG is working on SVG 1.2 full again, it will be revisited.

              If it turns out to be a feature that is very complex and unreliable
              to implement (as Thomas said), it may be skipped, though.

              Andreas
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