Largest contentful paint is one big gatsby-background-image and very slow

问题

For those stumbling on this question wondering how to improve their lighthouse score in general, I posted an answer on this topic on another question with lots of general tips.

I'm running PageSpeed insights and my biggest problem is the largest contentful paint, at about 8-10 seconds. Below they list my largest contentful paint element

Largest Contentful Paint element 1 element found
This is the largest contentful element painted within the viewport. Learn More
Element

This is the a paragraph that appears above here    
<section class="mainBgImage gbi--716926567-eDXcajFRMpQ2F1s7wNgLk1" style="background-position:center top;background-repeat:no-repeat;background-size:cover;position:relative;opacity:0.99" role="img">

This element is an image that spans my whole website in the background. It was originally a 1.2 MB png that i load using ...GatsbyImageSharpFluid_withWebp_noBase64 with a maxWidth of 1950.

This is the code for how I render it

    import BackgroundImage from 'gatsby-background-image';

    ...

      <BackgroundImage
        Tag="section"
        role="img"
        className='mainBgImage'
        fadeIn={false}
        // style={{objectFit: 'contain',  width: '100%' }}
        style={{
          opacity: 0.03,
          backgroundPosition: "center top",
          
        }}
        fluid={wheatImgProps}
      >
          {children}
      </BackgroundImage>

And this is the static graphql query

    const data = useStaticQuery(graphql
        `query LayoutQuery {
          wheatImg: file(
            extension: {regex: "/(jpg)|(jpeg)|(png)/"},
            name: {eq: "wheat-background"}
          ) {
            childImageSharp {
              fluid(maxWidth: 1950) {
                ...GatsbyImageSharpFluid_withWebp_noBase64
              }
            }
          }
        }
        `
      )

回答1:

Turns out the solution was to split my background image into 2. One for "above the fold"(Whats visible without scrolling) and one for "below the fold". I also found this image compressor website to be one of the most helpful and straight forward when it came to reducing my file size.

I then created an absolutely positioned div which looked like

const BGImg = ({img, className}:{img:FluidObject, className?:string}) => (
    <Img
        Tag="section"
        className={className}
        durationFadeIn={250}
          
        style={{
            opacity: 0.03,
            minWidth:"100%",
            objectFit: 'cover',
            objectPosition: "center top",
        }}
        fluid={img}
    />
)

...

<div id='layout'>
    <div id='bgImageContainer'>
        <BGImg img={above_the_fold_bg} />
        <BGImg img={below_the_fold_bg}  />
    </div>
...

with styling that looked like

#bgImageContainer{
    position: absolute;
    z-index: -999;
    min-width:100%;
    min-height:100%;
    display:flex;
    flex-direction: column;
    justify-content: flex-end;
    align-self: stretch;
}

#layout{
    overflow: hidden;
    position: relative;
}

来源：https://stackoverflow.com/questions/62892416/largest-contentful-paint-is-one-big-gatsby-background-image-and-very-slow

标签

gatsby

pagespeed

sharp

pagespeed-insights

gatsby-image