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How to create simple way to rotate region Turn on/off line numbers in source code. Switch to Orginial background IDE or DSP color Comment or reply to this aritlce/tip for discussion. Bookmark this article to my favorite article(s). Print this article
03-Jun-03
Category
VCL-General
Language
Delphi 7.x
Views
67
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Publisher:
DSP, Administrator
Reference URL:
DKB
			Author: Nik Ozniev 

Simple function returning rotated region. Pprocedure doing the same with source 
region.

Answer:

It's the simple function returning new region rotated to the angle that you want 
around the source region. Source region doesn't change. 

The second procedure does the same with source region without creating new region. 

I hope this will be useful. 
Comments are provided along the code 
1   
2   function _RotateRgn(ARgn: HRGN; ADegree: Real): HRGN;
3   var
4     wXFORM: XFORM; // transformation structure, see Windows API
5     kRgnD: DWord; // count of RGNDATA structures in region
6     RgnData: PRgnData; // pointer to region data
7     Rt: TRect;
8     kX, kY: Integer;
9   begin
10    if (ARgn = 0) or (ADegree = 0) then
11      Exit;
12  
13    // Get region's surrounding rectangular
14    GetRgnBox(ARgn, Rt);
15  
16    // Move source region so that the centre of its surrounding rectangular
17    // goes to the left top corner of a window
18    kX := Rt.Left + (Rt.Right - Rt.Left) div 2;
19    kY := Rt.Top + (Rt.Bottom - Rt.Top) div 2;
20    OffsetRgn(ARgn, -kX, -kY);
21  
22    // Fill XFORM according to task (rotate region)
23    FillChar(wXFORM, SizeOf(wXFORM), #0);
24    wXFORM.eM11 := Cos(ADegree / 180 * pi);
25    wXFORM.eM12 := -Sin(ADegree / 180 * pi);
26    wXFORM.eM21 := -wXFORM.eM12;
27    wXFORM.eM22 := wXFORM.eM11;
28  
29    // Prepare buffer to store region data
30    kRgnD := GetRegionData(ARgn, 0, nil);
31    GetMem(RgnData, SizeOf(RGNDATA) * kRgnD);
32    // ..and fill the buffer with region's data
33    GetRegionData(ARgn, kRgnD, RgnData);
34    // ..move source region to its initial position
35    OffsetRgn(ARgn, kX, kY);
36  
37    // Create output region using data in the buffer and transformation wXFORM
38    Result := ExtCreateRegion(@wXFORM, kRgnD, RgnData^);
39    // Move output region on a place of source region
40    OffsetRgn(Result, kX, kY);
41    FreeMem(RgnData);
42  end;
43  
44  procedure _RotateRgnEx(var ARgn: HRGN; ADegree: Real);
45  var
46    wXFORM: XFORM; // transformation structure, see Windows API
47    kRgnD: DWord; // count of RGNDATA structures in region
48    RgnData: PRgnData; // pointer to region data
49    Rt: TRect;
50    kX, kY: Integer;
51  begin
52    if (ARgn = 0) or (ADegree = 0) then
53      Exit;
54  
55    // Get region's surrounding rectangular
56    GetRgnBox(ARgn, Rt);
57  
58    // Move source region so that the centre of its surrounding rectangular
59    // goes to the left top corner of a window
60    kX := Rt.Left + (Rt.Right - Rt.Left) div 2;
61    kY := Rt.Top + (Rt.Bottom - Rt.Top) div 2;
62    OffsetRgn(ARgn, -kX, -kY);
63  
64    // Fill XFORM according to task (rotate region)
65    FillChar(wXFORM, SizeOf(wXFORM), #0);
66    wXFORM.eM11 := Cos(ADegree / 180 * pi);
67    wXFORM.eM12 := -Sin(ADegree / 180 * pi);
68    wXFORM.eM21 := -wXFORM.eM12;
69    wXFORM.eM22 := wXFORM.eM11;
70  
71    // Prepare buffer to store region data
72    kRgnD := GetRegionData(ARgn, 0, nil);
73    GetMem(RgnData, SizeOf(RGNDATA) * kRgnD);
74    // ..and fill the buffer with region's data
75    GetRegionData(ARgn, kRgnD, RgnData);
76    // ..delete source region
77    DeleteObject(ARgn);
78  
79    // Create new region using data in the buffer and transformation wXFORM
80    ARgn := ExtCreateRegion(@wXFORM, kRgnD, RgnData^);
81    // Move output region to the origin place
82    OffsetRgn(ARgn, kX, kY);
83    FreeMem(RgnData);
84  end;


			
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