chromedp screenshot example

fullscreenshot.go

package main

import (
	"context"
	"io/ioutil"
	"log"
	"math"
	"time"

	"github.com/chromedp/cdproto/emulation"
	"github.com/chromedp/cdproto/page"
	"github.com/chromedp/chromedp"
)

func main() {
	// create chrome instance
	ctx, cancel := chromedp.NewContext(
		context.Background(),
		chromedp.WithLogf(log.Printf),
	)
	defer cancel()

	// create a timeout
	ctx, cancel = context.WithTimeout(ctx, 15*time.Second)
	defer cancel()

	var img []byte
	err := chromedp.Run(ctx,
		chromedp.Navigate(`https://golang.org/pkg/time/`),
		chromedp.WaitVisible(`body > footer`), // wait for footer element is visible (ie, page is loaded)
		FullScreenshot(90, &img),
	)
	if err != nil {
		log.Fatal(err)
	}
	if err := ioutil.WriteFile("fullScreenshot.png", img, 0644); err != nil {
		log.Fatal(err)
	}
}

func FullScreenshot(quality int64, result *[]byte) chromedp.Action {
	return chromedp.ActionFunc(func(ctx context.Context) error {
		// get layout metrics
		_, _, contentSize, err := page.GetLayoutMetrics().Do(ctx)
		if err != nil {
			return err
		}

		width, height := int64(math.Ceil(contentSize.Width)), int64(math.Ceil(contentSize.Height))

		// force viewport emulation
		err = emulation.SetDeviceMetricsOverride(width, height, 1, false).
			WithScreenOrientation(&emulation.ScreenOrientation{
				Type:  emulation.OrientationTypePortraitPrimary,
				Angle: 0,
			}).
			Do(ctx)
		if err != nil {
			return err
		}

		// capture screenshot
		*result, err = page.CaptureScreenshot().
			WithQuality(quality).
			WithClip(&page.Viewport{
				X:      contentSize.X,
				Y:      contentSize.Y,
				Width:  contentSize.Width,
				Height: contentSize.Height,
				Scale:  1,
			}).Do(ctx)
		if err != nil {
			return err
		}
		return nil
	})
}

contentSize is nil with recent versions of chromerdp / chromium