Gdiplus [48]: igpmatrix (iii) Matrix Rotation

A matrix rotation angle is associated with four data types: M11, M12, m21, and m22. The calculation formula is as follows:

 
┏ ┓ ┃ Cos (r) sin (r) 0 ┃-sin (r) Cos (r) 0 ┃ DX dy 1 ┃ ┗ ┛ // The r here is not the angle of the radian; The radian calculation method is: r = angle * PI/180.

  
 

The following two paragraphsProgramThe above formula is compared and tested:

// Var M: igpmatrix; begin M: = tgpmatrix. create; M. rotate (90); showmessagefmt ('% F % F', [M. elements. m11, M. elements. m12]); // 0.00 1.00 showmessagefmt ('% F % F', [M. elements. m21, M. elements. m22]); //-1.00 0.00 M. reset; M. rotate (-30); showmessagefmt ('% F % F', [M. elements. m11, M. elements. m12]); // 0.87-0.50 showmessagefmt ('% F % F', [M. elements. m21, M. elements. m22]); // 0.50 0.87end; // var R: single; M11, M12, m21, m22: single; Begin R: = 90 * PI/180; M11: = cos (r); M12: = sin (r); m21: =-sin (r); m22: = cos (r); showmessagefmt ('% F % F ', [M11, M12]); // 0.00 1.00 showmessagefmt ('% F % F', [m21, m22]); //-1.00 0.00 R: =-30 * PI/180; M11: = cos (r); M12: = sin (r); m21: =-sin (r); m22: = cos (r); showmessagefmt ('% F % F', [M11, M12]); // 0.87-0.50 showmessagefmt (' % F % F', [m21, m22]); // 0.50 0.87end;

  
 

Observe the rotation effect of a point (90 degrees from blue to red ):

Uses gdiplus; procedure merge (Sender: tobject); var graphics: igpgraphics; pen: igppen; brush: igpsolidbrush; matrix: igpmatrix; I: integer; Pt: tgppointf; begin clientwidth: = 300; clientheight: = 200; pen: = tgppen. create ($ ffe0e0e0); brush: = tgpsolidbrush. create ($ ff0000ff); graphics: = tgpgraphics. create (handle); // draw the coordinate system graphics. clear ($ ffffffff); for I: = 1 to clientwidth Div 10 do graphics. drawline (pen, tgppoint. create (I * 10, 0), tgppoint. create (I * 10, clientheight); for I: = 1 to clientheight Div 10 do graphics. drawline (pen, tgppoint. create (0, I * 10), tgppoint. create (clientwidth, I * 10); pen. color: = $ ffb0b0b0; graphics. drawline (pen, tgppoint. create (clientwidth Div 2, 0), tgppoint. create (clientwidth Div 2, clientheight); graphics. drawline (pen, tgppoint. create (0, clientheight Div 2), tgppoint. create (clientwidth, clientheight Div 2); // Pan coordinate system graphics. translatetransform (clientwidth Div 2, clientheight Div 2); graphics. pixeloffsetmode: = pixeloffsetmodehalf; graphics. drawellipse (pen,-2,-2, 5, 5); // if there is a vertex (80,-40), draw the vertex PT in blue. initialize (80,-40); graphics. drawline (pen, tgppointf. create (0, 0), Pt); graphics. fillrectangle (brush, PT. x-2, PT. y-2, 5, 5); // Rotate 90 degrees, redraw This vertex graphics with red. rotatetransform (90); graphics. pixeloffsetmode: = pixeloffsetmodehalf; brush. color: = $ ffff0000; graphics. drawline (pen, tgppointf. create (0, 0), Pt); graphics. fillrectangle (brush, PT. x-2, PT. y-2, 5, 5); end;
 
   
 

Rotating and transforming igpmatrix. Rotate () or igpgraphics. rotatetransform has a circle (0, 0;

Igpmatrix. rotateat () can rotate around a specified point, for example:

 
Uses gdiplus; Procedure tform1.formpaint (Sender: tobject); var graphics: igpgraphics; matrix: igpmatrix; pen: igppen; rect: tgprect; begin graphics: = tgpgraphics. create (handle); pen: = tgppen. create ($ ffd0d0d0, 2); rect. initialize (50, 30, 80, 80); graphics. clear ($ ffffffff); graphics. drawrectangle (pen, rect); matrix: = tgpmatrix. create; matrix. rotateat (45, tgppointf. create (rect. X + rect. width/2, rect. Y + rect. height/2); graphics. multiplytransform (matrix); pen. color: = $80ff0000; graphics. drawrectangle (pen, rect); end;