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Tutorial 3. Working with vector objects Next | Previous
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Creating non-rectangular windows
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In this example we will use vector objects to vectorize some image regions. Then we will use the regions obtained to create non-standard windows by using the SetWindowRgn API function.
First, we create a new project with two forms: Form1 and Form2. Then we remove Form2 from the auto-creation list (use the Project/Options menu, Forms tab, ‘>>’ button).
We next drop TZBitmapLink, TZImageBox and TZMarkerLayer (PixeLook palette page) onto Form1 and set the following properties in the Object Inspector (see Tutorial 1 for details of the TZBitmapLink component):
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ZBitmapLink1.MappingMode =mmDisk
ZBitmapLink1.Active = true
ZImageBox1.Align = alClient
ZImageBox1.BitmapLink = ZBitmapLink1
ZMarkerLayer1.Parent = ZImageBox1, this attaches the layer to ZImageBox1
ZMarkerLayer1.Active = true, this activates the layer, so that it can accept mouse messages
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As we will outline image regions, we need only closed vector objects. So we set the following elements of the ZMarkerLayer1.ObjectTypes property:
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otPoint = false
otLine = false
otPolygon = false
otRect = true
otVector = false
otCircle = true
otEllipse = true
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Then we create the Form1.OnCreate event handler, where the second form is created:
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procedure TForm1.FormCreate(Sender: TObject);
begin
Form2:=TForm2.Create(Self);
Form2.Show;
// place your own image here
ZBitmapLink1.FileName:='c:/padlock.bmp';
end;
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We now drop the standard TImage component onto Form2, and set the following properties in the Object Inspector:
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With these properties, Form2 will look like just an image (no caption or borders).
Using the Object Inspector we load the 'c:/padlock.bmp' image to the Form2.Image1.Picture object.
We then create the second piece of code (ZMarkerLayer1.OnMouseUp event handler) where the shape of Form2 is changed according to vector objects:
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procedure TForm1.ZMarkerLayer1MouseUp(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Double);
var P:array of TPoint;
Num:array of integer;
Point:TDPoint;
N,i,j:integer;
R:HRGN;
begin
with ZMarkerLayer1 do
begin
//Count a number of points in all vector objects
N:=0;
for i:=0 to Objects.Count-1 do
inc(N,Objects[i].SplineCount);
//Allocate an array for all points
SetLength(P,N);
// Allocate an array of integers, each of which specifies the number of points in one of the polygons
SetLength(Num,Objects.Count);
// Copy all points of vector objects to the array
N:=0;
for i:=0 to Objects.Count-1 do //iterate over all objects
begin
Num[i]:=Objects[i].SplineCount;
for j:=0 to Objects[i].SplineCount-1 do //iterate over all object's points
begin
Point:=Objects[i].Spline[j]; // get next point
P[N].X:=round(Point.X);
P[N].Y:=round(Point.Y);
inc(N);
end;
end;
// Create a Windows region from all vector objects
R:=CreatePolyPolygonRgn(P[0],Num[0],Objects.Count,ALTERNATE);
end;
//Change shape of Form2 according to new region
SetWindowRgn(Form2.Handle,R,true);
end;
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Now you can run the program and put a few vector objects onto the Form1. You will see that Form2 changes its shape according to the vector objects. You can select rectangles, circles, ellipses or polygons. A polygon can be smoothed using the context menu or the toolbar buttons. The following picture shows an example, where the region consists of 2 ellipses, 2 rectangles and 3 polygons:
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