http://www.quickpdf.org/forum/ Copyright (c) 2006-2013 Web Wiz Forums - All Rights Reserved. Tue, 09 Jun 2026 09:45:01 +0000 Fri, 03 Feb 2012 20:18:11 +0000 http://blogs.law.harvard.edu/tech/rss Web Wiz Forums 11.01 360 www.quickpdf.org/forum/RSS_post_feed.asp?TID=2124 http://www.quickpdf.org/forum/forum_images/QPDF_Forum_Title.png http://www.quickpdf.org/forum/ http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9061.html#9061 Author: edvoigt
Subject: 2124
Posted: 03 Feb 12 at 8:18PM

Hi,

there is something more to say. Because hatch or not hatch is a question of orientation.

My first example shows a normal drawn box and for clipping a path consisting of a circle and a hatch-box in it. Here the source:
  QP.SetOrigin(0);                 // Bottomleft
  QP.SetMeasurementUnits(1);       // Millimeter
  QP.SetPageDimensions(210, 297);

  QP.SetLineWidth(0.1);
  QP.SetLineColor(1, 0, 0);
  QP.SetFillColor(1, 1, 0);
  x0 := 25; x1 := 175;
  y0 := 170; y1 := 270;
  r := 70;
  // 1. draw without clipping
  QP.DrawBox(x0, y1, x1-x0, y1-y0, 1);
  QP.DrawCircle((x0+x1)/2, y1-r, r, 0);

  QP.SaveState; // for later use without clipping
  // 2. define clipping path
  QP.StartPath((x0+x1)/2, y1);
  QP.AddArcToPath((x0+x1)/2, y1-r, 360);  // the "normal" path for clipping
  // 3. hatch-box-building
  // hatch or not hatch is a question of orientation
  QP.MovePath(x0+20, y0+75); // upper left corner
  QP.AddLineToPath(x0+20, y0+50); // lower left
  QP.AddLineToPath(x0+50, y0+50); // lower right
  QP.AddLineToPath(x0+50, y0+75); // upper right
  QP.AddLineToPath(x0+20, y0+75); // close hatch, important!
  QP.SetClippingPath;
  // 4. draw clipped things
  // it will be drawn only inside the first circle and outside our hatchbox
  QP.DrawBox(x0, y1, x1-x0, y1-y0, 0);
  for i:=0 to 52 do QP.DrawLine(x1-i*5, y0, x1, y0+i*5);
  QP.SetFillColor(0, 1, 0);
  QP.DrawCircle(x0+50, y0+75, 10, 2);

  QP.LoadState; // stop clipping from here

  QP.SetLineColor(0, 0, 0);
  QP.DrawLine(x0, y0, (x0+x1)/2, y1);

The second example is more interessting. Using four lines two triangles are builded, but only one of them becomes to be hatch. 

That's so because of orientation during AddLineToPath-sequence.

Wandering from P1 over P2 to P3 upper triangle is ever on your right side. But the other Triangle is on the way from P3 over P4 to P1 on left side. Areas on right side are are parts of the path, but areas on left side dont't belong to path, they are hatches.

Source for this:
  x0 := 100; y1 := y0-50; y0 := 20;  r := 30;
  QP.SaveState; // for later use without clipping
  QP.StartPath(x0-r-5, y1+5);
//first a box as clipping area
  QP.AddLineToPath(x0+2*r, y1);
  QP.AddLineToPath(x0+2*r, y0-1);
  QP.AddLineToPath(x0-r, y0-1);
  QP.AddLineToPath(x0-r, y1);
// and now a special kind of half hatch
  QP.MovePath(x0, y1);
  QP.AddLineToPath(x0+r, y1);
  QP.AddLineToPath(x0-r, y0);
  QP.AddLineToPath(x0+r, y0);
  QP.AddLineToPath(x0, y1);
  QP.SetClippingPath;
  QP.DrawBox(x0-r, y1, 2*r, y1-y0, 1);
// show hatch construction
  QP.SetLineColor(0, 0, 0);
  QP.SetLineWidth(1.0);
  QP.DrawLine(x0, y1, x0+r, y1); // show the contour
  QP.DrawLine(x0+r, y1, x0-r, y0);
  QP.DrawLine(x0-r, y0, x0+r, y0);
  QP.DrawLine(x0+r, y0, x0, y1);

  QP.LoadState; // stop clipping now again
  QP.DrawText(x0, y1+2, 'P1');
  QP.DrawText(x0+r, y1+2, 'P2');
  QP.DrawText(x0-r, y0-5, 'P3');
  QP.DrawText(x0+r, y0-5, 'P4');

Cheers,
Werner


Edited by edvoigt - 03 Feb 12 at 8:20PM]]> Fri, 03 Feb 2012 20:18:11 +0000 http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9061.html#9061 http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9056.html#9056 Author: kaiken1987
Subject: 2124
Posted: 02 Feb 12 at 1:58PM

Thank you that worked for me very well.]]> Thu, 02 Feb 2012 13:58:03 +0000 http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9056.html#9056 http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9040.html#9040 Author: AndrewC
Subject: 2124
Posted: 01 Feb 12 at 8:25AM

Here is some code to draw a hollow star..

// Draw a hollow star

            QP.SetFillColor(1, 0, 0);
            QP.SetLineColor(0, 1, 0);

            QP.StartPath(100, 60);
            QP.AddLineToPath(306, 600);
            QP.AddLineToPath(512, 60);
            QP.AddLineToPath(20, 400);
            QP.AddLineToPath(592, 400);
            QP.ClosePath();

            QP.DrawPathEvenOdd(2);

            // Draw a hollow donut

            QP.NewPage();

            QP.SetFillColor(1, 0, 0);
            QP.SetLineColor(0, 1, 0);

            QP.StartPath(100, 200);
            QP.AddArcToPath(200, 200, 360);
            QP.MovePath(150, 200);
            QP.AddArcToPath(200, 200, 360);
            QP.ClosePath();
            QP.DrawPathEvenOdd(2);

]]> Wed, 01 Feb 2012 08:25:39 +0000 http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9040.html#9040 http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9038.html#9038 Author: kaiken1987
Subject: 2124
Posted: 31 Jan 12 at 2:56PM

I'm trying to find a way to draw filled polygons with holes in them, something like the widows GDI polypolygon function. The only way I've been able to figure out is to call GetCanvasDC, RenderToDC, use the polypolygon function and then call LoadFromCanvasDC. That seems terribly slow and inefficient and I assume the must be a better way then that.]]> Tue, 31 Jan 2012 14:56:59 +0000 http://www.quickpdf.org/forum/how-to-draw-hatches_topic2124_post9038.html#9038