You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: Form1Impl.go
    path of file: ./repos/govcl/samples/intfTest
    
    the code of the file until where you have to start completion: // 在这里写你的事件

package main

import (
	"github.com/ying32/govcl/vcl"
	"github.com/ying32/govcl/vcl/rtl"
	"github.com/ying32/govcl/vcl/types"
)

//::private::
type TFor
    
func (f *TForm1) OnButton1Click(sender vcl.IObject) {
	// 屏幕截图
	dc := rtl.GetDC(0)         // windows桌面
	defer rtl.ReleaseDC(0, dc) // 一定要释放
	bmp := vcl.NewBitmap()
	defer bmp.Free()
	bmp.LoadFromDevice(dc)
	f.Image1.Picture().Assign(bmp)
}