Using FPVectorial.
lazarus / 39-Graphics

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cov · 2013-04-12 06:50

How do you use FPVectorial?

I want to display a SVG file on a TImage.

Is this possible?

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felipemdc · 2013-04-12 07:06

Yes, it is possible thought the SVG support is not very advanced at
the moment. Luckly I am working on it at the moment, so I think that
in 1 month or so the SVG reader should be getting much better in the
following weeks and months.

In general you should study the example project, it is in Lazarus-ccr
subversion in the folder applications/fpvviewer

To render a SVG image you should do something like this:

var
  Vec: TvVectorialDocument;
begin
  Vec := TvVectorialDocument.Create;
  try
    Vec.ReadFromFile(editFileName.FileName);
    Vec.GetPage(0).DrawBackground(Drawer.Drawing.Canvas);
    Vec.GetPage(0).Render(
      Drawer.Drawing.Canvas,
      0,
      Drawer.Drawing.Height,
      1,
      -1);
    Drawer.Invalidate;
  finally
    Vec.Free;
  end;

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cov · 2013-04-12 08:07

Yes, I have been looking at the VPViewer project (downloaded from
svn).

I'm not clear of how to draw on the TImage canvas.

I've cut-and-pasted your code above and get a SIGSEGV error on
Vec.GetPage(0).DrawBackground(Drawer.Drawing.Canvas);

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felipemdc · 2013-04-12 09:03

You have to post all your code, I can guess with so little
information.

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cov · 2013-04-12 11:49

Code: [Select]procedure TForm1.FormShow(Sender: TObject);
var
  Vec: TvVectorialDocument;
  CanvasSize: TPoint;
begin
    with OpenDialog1 do
      if Execute then
      begin
        Vec := TvVectorialDocument.Create;
        try
          Vec.ReadFromFile(FileName);
         
Vec.GetPage(0).DrawBackground(Drawer.Drawing.Canvas);//<-SIGSEGV here
          Vec.GetPage(0).Render(
              Drawer.Drawing.Canvas,
              0,
              Drawer.Drawing.Height,
              1,
              -1);
          Drawer.Invalidate;
        finally
          Vec.Free;
        end;
      end;
end;  
That's it.

Just copied-and-pasted your code, effectively.

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felipemdc · 2013-04-12 11:53

It should not compile at all, since you probably have no Drawer object
in your code. You need to substitute "Drawer.Drawing.Canvas" with your
destination Canvas. What is the name of your TImage control? Try
something like MyImage.Picture.Bitmap.Canvas and
MyImage.Picture.Bitmap.Height respectively for the Canvas and the
Height

Also, creating a dialog in OnShow does not look a good idea, I'd
rather place a button to run this code.

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cov · 2013-04-12 12:19

Great!

That's what I was asking, thank you!

I'll give that a go...

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cov · 2013-04-12 12:58

Thanks, Felipe; that works.

Code: [Select]  Image1.Canvas.Brush.Color:=clWhite;
  Image1.Canvas.FillRect(0,0,Image1.Width,Image1.Height);
  Vec.ReadFromFile(sFname);
  Vec.GetPage(0).DrawBackground(Image1.Canvas);
  Vec.GetPage(0).Render(
              Image1.Canvas,
              0,
              Image1.Height,
              1,
              -1);
  Image1.Invalidate; //<- Not sure what this does...

The Image Canvas needs to be filled with white before the SVG is drawn
otherwise it appears to be filled with black and (as the image appears
to be drawn with a black pen only) no image appears.

Also the SVG appears to be mostly drawn off screen, no matter what
size the Image Canvas is (2 screenshots attached)

1. Is there a way to control the placement of the SVG image?

2. Is it possible to control the colour of the pen so that the image
is rendered in it's original colours?

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felipemdc · 2013-04-12 13:03

Quote from: cov on April 12, 2013, 02:58:33 pm1. Is there a way to
control the placement of the SVG image?

Yes, that's what the 2nd and 3rd parameters are for. Try for example:

  Vec.GetPage(0).Render(
              Image1.Canvas,
              0,
              Image1.Height - 200,

Quote2. Is it possible to control the colour of the pen so that the
image is rendered in it's original colours?
Use the latest subversion fpvectorial. I fixed a problem with SVG
colors some days ago.

If this doesn't solve the problem, please attach the SVG file.

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cov · 2013-04-12 14:12

Thanks Felipe.

Code: [Select]  Vec.GetPage(0).Render(Image1.Canvas,0,0,1,-1);   
Seems to work. How do you resize the image? It's awfully small.

I've downloaded the SVN from today: the pen is still black although
the image should be in colour.

The SVG file is here (too large to be uploaded).

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felipemdc · 2013-04-12 14:15

Quote from: cov on April 12, 2013, 04:12:43 pmSeems to work. How do
you resize the image? It's awfully small.
That's what the 4th and 5th parameters do. To enlarge it by 2x for
example do:

  Vec.GetPage(0).Render(Image1.Canvas,0,Image1.Height,2,-2);

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felipemdc · 2013-04-12 14:17

If this file was originally made with AutoCad you could try opening a
DXF version of it in fpvectorial for now. DXF and PostScript are the
best supported formats at the moment. I am working on improving the
SVG support.

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cov · 2013-04-12 14:36

Okay, If that will control the size, that would be great. Also should
give the cabability of being able to zoom in and out.

Is the colour enabled in the latest code? That would be quite
important. Perhaps the svn update didn't take?

Is it possible to change the colours? Maybe have the background as
black and the black lines drawn in white?

Using a DXF file wouldn't quite suit my purpose which is to have a
thumbnail so that the user can check if he has the right drawing. WMF
would be OK, though.

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felipemdc · 2013-04-12 14:50

Quote from: cov on April 12, 2013, 04:36:43 pmIs the colour enabled in
the latest code? That would be quite important. Perhaps the svn update
didn't take?
It is, but it seams that your image uses something else. SVG is really
huge ... there are 100s of ways of writing the same drawing in SVG.
And this complicates it a lot.

QuoteIs it possible to change the colours? Maybe have the background
as black and the black lines drawn in white?
Yes, check the "force background color" option in fpvviewer, thought I
wrote this option for DXF, so I'm not sure how it will work in SVG.

QuoteUsing a DXF file wouldn't quite suit my purpose which is to have
a thumbnail so that the user can check if he has the right drawing.
WMF would be OK, though.
I don't see why it would not be suitable. DXF is fully vectorial. Try
opening a DXF file with fpvviewer and use the mouse whell to zoom. You
can zoom-in/out as much as you want in DXF.

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cov · 2013-04-12 15:00

Okay, I'll try that.

The reason DXF isn't suitable is that an AutoCAD drawing can be
(usually is) split into an area called Modelspace with one or more
'Paperspace' views that will incorporate information such as
annotations, Drawing borders, titleblocks, revision information, etc
that won't necessarily be on the modelspace area.

The SVG file is a snapshot that takes the Paperspace view that was
last looked at (or the Modelspace, if the Drawing was saved in that
mode).

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cov · 2013-04-12 20:44

Hmmm.

Getting a SIGSEGV exception.

I've setup the Form.Image1 onShow:Code: [Select]    Vec :=
TvVectorialDocument.Create;
    Image1.Canvas.Brush.Color:=clWhite;
    Image1.Canvas.FillRect(0,0,Image1.Width,Image1.Height);
    Vec.ReadFromFile(tmpPath+'thumb.svg');
Then Form1.FormResize:Code: [Select]  scale:=Image1.Width/250;
  Vec.GetPage(0).DrawBackground(Image1.Canvas);
  Vec.GetPage(0).Render(
            Image1.Canvas,
            0,
            0,
            scale,
            -scale);
  Image1.Invalidate;
This gives a SIGSEGV in 'fpvectorial.pas' on line 4176 Code:
[Select]Result := TvVectorialPage(FPages.Items[AIndex]); 
How do you alter the size of the Image to match resizing of the Form?

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felipemdc · 2013-04-12 21:16

OnResize is probably being called after OnShow. Essential code should
be on OnCreate, not OnShow.

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zamtmn · 2013-04-14 19:57

felipemdc
QuoteThat's what the 4th and 5th parameters do. To enlarge it by 2x
for example do:
  Vec.GetPage(0).Render(Image1.Canvas,0,Image1.Height,2,-2);
To correctly display the drawing you need to know its overall
dimensions. It would be nice to have a calculation
ADestX,ADestY,AMulX,AMulY within the FPV library for a particular
ADest

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cov · 2013-04-25 12:14

Quote from: felipemdc on April 12, 2013, 09:06:05 amYes, it is
possible thought the SVG support is not very advanced at the moment.
Luckly I am working on it at the moment, so I think that in 1 month or
so the SVG reader should be getting much better in the following weeks
and months.

In general you should study the example project, it is in Lazarus-ccr
subversion in the folder applications/fpvviewer


Hi Felipe,

How are you getting on with your SVG implementation? Will it be able
to read the SVG file that I showed you?

I've put together a very basic parser which draws directly on the
Image TCanvas, and while it sort of works, it's not very slick.