134 lines
3.7 KiB
C#
134 lines
3.7 KiB
C#
using System;
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using Cairo;
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class Knockout
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{
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void OvalPath (Context ctx, double xc, double yc, double xr, double yr)
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{
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Matrix m = ctx.Matrix;
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ctx.Translate (xc, yc);
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ctx.Scale (1.0, yr / xr);
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ctx.MoveTo (xr, 0.0);
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ctx.Arc (0, 0, xr, 0, 2 * Math.PI);
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ctx.ClosePath ();
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ctx.Matrix = m;
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}
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void FillChecks (Context ctx, int x, int y, int width, int height)
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{
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int CHECK_SIZE = 32;
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ctx.Save ();
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Surface check = ctx.Target.CreateSimilar (Content.Color, 2 * CHECK_SIZE, 2 * CHECK_SIZE);
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// draw the check
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Context cr2 = new Context (check);
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cr2.Operator = Operator.Source;
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cr2.Color = new Color (0.4, 0.4, 0.4);
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cr2.Rectangle (0, 0, 2 * CHECK_SIZE, 2 * CHECK_SIZE);
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cr2.Fill ();
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cr2.Color = new Color (0.7, 0.7, 0.7);
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cr2.Rectangle (x, y, CHECK_SIZE, CHECK_SIZE);
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cr2.Fill ();
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cr2.Rectangle (x + CHECK_SIZE, y + CHECK_SIZE, CHECK_SIZE, CHECK_SIZE);
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cr2.Fill ();
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//cr2.Destroy ();
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// Fill the whole surface with the check
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SurfacePattern check_pattern = new SurfacePattern (check);
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check_pattern.Extend = Extend.Repeat;
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ctx.Source = check_pattern;
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ctx.Rectangle (0, 0, width, height);
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ctx.Fill ();
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check_pattern.Destroy ();
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check.Destroy ();
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ctx.Restore ();
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}
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void Draw3Circles (Context ctx, int xc, int yc, double radius, double alpha)
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{
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double subradius = radius * (2 / 3.0 - 0.1);
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ctx.Color = new Color (1.0, 0.0, 0.0, alpha);
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OvalPath (ctx, xc + radius / 3.0 * Math.Cos (Math.PI * 0.5), yc - radius / 3.0 * Math.Sin (Math.PI * 0.5), subradius, subradius);
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ctx.Fill ();
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ctx.Color = new Color (0.0, 1.0, 0.0, alpha);
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OvalPath (ctx, xc + radius / 3.0 * Math.Cos (Math.PI * (0.5 + 2 / 0.3)), yc - radius / 3.0 * Math.Sin (Math.PI * (0.5 + 2 / 0.3)), subradius, subradius);
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ctx.Fill ();
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ctx.Color = new Color (0.0, 0.0, 1.0, alpha);
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OvalPath (ctx, xc + radius / 3.0 * Math.Cos (Math.PI * (0.5 + 4 / 0.3)), yc - radius / 3.0 * Math.Sin (Math.PI * (0.5 + 4 / 0.3)), subradius, subradius);
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ctx.Fill ();
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}
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void Draw (Context ctx, int width, int height)
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{
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double radius = 0.5 * Math.Min (width, height) - 10;
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int xc = width / 2;
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int yc = height / 2;
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Surface overlay = ctx.Target.CreateSimilar (Content.ColorAlpha, width, height);
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Surface punch = ctx.Target.CreateSimilar (Content.Alpha, width, height);
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Surface circles = ctx.Target.CreateSimilar (Content.ColorAlpha, width, height);
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FillChecks (ctx, 0, 0, width, height);
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ctx.Save ();
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// Draw a black circle on the overlay
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Context cr_overlay = new Context (overlay);
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cr_overlay.Color = new Color (0.0, 0.0, 0.0);
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OvalPath (cr_overlay, xc, yc, radius, radius);
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cr_overlay.Fill ();
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// Draw 3 circles to the punch surface, then cut
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// that out of the main circle in the overlay
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Context cr_tmp = new Context (punch);
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Draw3Circles (cr_tmp, xc, yc, radius, 1.0);
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//cr_tmp.Destroy ();
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cr_overlay.Operator = Operator.DestOut;
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cr_overlay.SetSourceSurface (punch, 0, 0);
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cr_overlay.Paint ();
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// Now draw the 3 circles in a subgroup again
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// at half intensity, and use OperatorAdd to join up
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// without seams.
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Context cr_circles = new Context (circles);
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cr_circles.Operator = Operator.Over;
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Draw3Circles (cr_circles, xc, yc, radius, 0.5);
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// cr_circles.Destroy ();
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cr_overlay.Operator = Operator.Add;
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cr_overlay.SetSourceSurface (circles, 0, 0);
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cr_overlay.Paint ();
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// cr_overlay.Destroy ();
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ctx.SetSourceSurface (overlay, 0, 0);
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ctx.Paint ();
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overlay.Destroy ();
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punch.Destroy ();
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circles.Destroy ();
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}
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static void Main ()
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{
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new Knockout ();
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}
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Knockout ()
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{
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Surface s = new ImageSurface (Format.ARGB32, 400, 400);
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Context ctx = new Context (s);
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Draw (ctx, 400, 400);
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s.WriteToPng ("knockout.png");
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}
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}
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