delphi - Take screenshot of specific part of screen -

i'm trying take screenshot of specific part of screen. here coordinates of part of screen want 'cut' :

left : 442 top : 440 right : 792 bottom : 520

that is, rectangle of width 350px , height of 80px. don't know how use copyrect achieve task, instead i'm getting blank image. here code :

function screenshot: boolean; var   bild : tbitmap;   c: tcanvas;   rect_source, rect_destination : trect; begin    c := tcanvas.create;    bild := tbitmap.create;    c.handle := getwindowdc(getdesktopwindow);    try      rect_source := rect(0, 0, screen.width, screen.height);      rect_destination := rect(442,440,792,520);      bild.width := 350;      bild.height := 80;      bild.canvas.copyrect(rect_destination, c, rect_source);      bild.savetofile('c:\users\admin\desktop\screen.bmp');        releasedc(0, c.handle);      bild.free;      c.free;    end; end; 

what doing here copying whole screen , draw @ coordinate rect(442,440,792,520); in new bitmap... off canvas.

the coordinate rect(442,440,792,520) correspond part want source bitmap. want copy "inside" new bitmap, within rect rect(0,0,350,80)

you can adjust rect :

 rect_source := rect(442,440,792,520);  rect_destination := rect(0,0,350,80); 

the rest of code seems correct.