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From Guess Who <davej...@yahoo.com>
Subject Re: Rasterized Image Pixels not aligned with SVG Source
Date Wed, 29 Oct 2003 20:09:03 GMT
Actually, I'm not sure how to use viewPort in this
example.  Should I specify the viewbox to be (0,0,
612,792)?  

How would I use the transcoder code with the viewbox?

One reason I don't use the viewbox is because I will
be using this program to handle svgdocs with more than
one page (more than one <g> tag). I intend to
enumerate through each <g> tag and transcode an image
for each group specifying a aoi that corresponds to
each rect.  Can I do this with viewbox? 

I compared the coords differences at the top and the
bottom coord and they are both off by about 8 pixels. 
The xcoords are not off at all. 

I am using a borderlayout and I am adding a canvas
(that draws the image) to the center.  I think if I
pad the canvas at the top with 8 pixels, I can
workaround the problem.  

The fact that the xcoords are fine, but the ycoords
are off by a fixed amount, makes me think that my
problem is the placement of the image in the canvas,
even though i place it at 0,0. 

--- Thomas DeWeese <Thomas.DeWeese@Kodak.com> wrote:
> Guess Who wrote:
> 
> > Yes actually there is a lot more to the story. I'm
> not
> > using the rasterizer, I'm using the transcoder. 
> > 
> > I am getting the rect width from the doc which is
> 612.
> > 
> > I need to scale the image down to 500 width so I
> get
> > the "scale factor" = 500/612 = .817
> 
>    Hmm is there a reason that using the 'viewBox'
> attribute
> on the outermost SVG wouldn't do what you want?
> (auto
> scale to fit viewing conditions).
> 
>    The code looks reasonable.
> 
> > Now when I view the image in an applet using awt,
> I
> > capture some elementary mouse events.  When I
> place
> > the mouse pointer on the upper-leftmost corner of
> the
> > upper-leftmost text letter in the awt image, I get
> a Y
> > coord of about 61.  Now when we look at the svg
> code
> > the uppermost text is positioned at about 84 and
> with
> > the scaleFactor, it translates to about 69.  It is
> off
> > by  69-61 = 8 pixels. 
> 
>    How certain are you that you are properly
> interpreting the
> mouse coords?  Does the error seem to 'scale' so
> it's larger
> at the right/bottom compared with left/top?
> 
> > I think you are right and I am probably using the
> > transcoding process wrong, but I'm not sure what
> to
> > do... 
> 
>    I would try using viewBox rather than mucking
> with the
> AOI.
> 
> > 
> > Thanks for your help with this.
> > 
> > --- Thomas DeWeese <Thomas.DeWeese@Kodak.com>
> wrote:
> > 
> >>Guess Who wrote:
> >>
> >>David? :)
> >>
> >>
> >>>I'm having a little trouble with images that were
> >>>transcoded with batik.  In particular, I'm
> working
> >>>with svg documents that contain almost all text
> >>>elements.  When the doc is transcoded into an
> >>
> >>image,
> >>
> >>>coords of the text that appears in the image
> don't
> >>>seem to correspond with the coords specified in
> >>
> >>the
> >>
> >>>svg doc. 
> >>>
> >>>I've already taken into account the aspectratio
> in
> >>>testing the coords' congruency.  
> >>>
> >>>Aspectratio = imgwidth/svg:aoiwidth
> >>
> >>    Actually the proper name for this is the
> 'scale
> >>factor'.
> >>The Aspect ratio is typically the width/height (or
> >>vice versa).
> >>
> >>
> >>>the aoi that i'm using is the rect element just
> >>
> >>inside
> >>
> >>>the page group.
> >>
> >>   Well that is the same as the default area of
> the
> >>SVG
> >>so the scale factor here should be 1 (as is when I
> >>tested it).
> >>
> >>
> >>>For instance, xcoord:image  = xcoord:svgdoc *
> >>>aspectratio
> >>>
> >>>Correct me if I am wrong about the above calcs. 
> >>
> >>Here
> >>
> >>>is the svg doc...
> >>
> >>   In the future using an attachment works much
> >>better as often
> >>things get munged by line-wrapping.  Also how are
> >>you generating
> >>the image?  When I use the svgrasterizer I get
> text
> >>exactly where
> >>I think it should be:
> >>
> >>./build.sh svgrasterizer -a 0,0,612,792 text.svg
> >>
> >>   But since your image seems to be scaled somehow
> I
> >>must assume
> >>you are not using the default w/h for rendering.
> >>
> >>
> >>
> >>
> > 
> >
>
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> > 
> > 
> > 
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> 
> 
> 
>
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