Dst... example for Delphi

Calculate the values to zoom in by 10 percent and center the image.

Lead1.AutoScroll := False;
Lead1.DstWidth := (Lead1.DstWidth * 110) div 100;
Lead1.DstHeight := (Lead1.DstHeight * 110) div 100;
Lead1.DstTop := (Lead1.Height - Lead1.DstHeight) div 2;
Lead1.DstLeft := (Lead1.Width - Lead1.DstWidth) div 2; 
{Set the clipping area to the same as the destination rectangle}
Lead1.DstClipWidth := Lead1.DstWidth;
Lead1.DstClipHeight := Lead1.DstHeight;
Lead1.DstClipTop := Lead1.DstTop;
Lead1.DstClipLeft := Lead1.DstLeft; 
{Redisplay the image}
Lead1.ForceRepaint;