The screenshot generated by FullScreenshot() from the chromedp package is too blurry, how can I improve it?-Golang-php.cn

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The screenshot generated by FullScreenshot() from the chromedp package is too blurry, how can I improve it?

Feb 14, 2024 pm 02:48 PM

chromedp 包中的 FullScreenshot() 生成的屏幕截图太模糊，我该如何改进？

php editor Yuzi has a question about the chromedp package that needs to be answered. The question is about the screenshot generated using FullScreenshot() being too blurry and an improved approach is needed. When using the chromedp package, the quality of the generated screenshots may not be as expected, which may be due to some incorrect configuration or parameter settings. Here are some possible improvements to help you get clearer screenshots.

Question content

As the title says, here is the result and my code. BTW, I'm using a very low-end machine.

func main() {

    chromectx, _ := chromedp.newcontext(context.background())
    emulation.setdevicemetricsoverride(1920, 1080, 1.0, false).do(chromectx)

    var width, height int64
    var b []byte
    err := chromedp.run(chromectx,
        chromedp.emulateviewport(10, 10),
        chromedp.navigate(`the content of the file is in the code block below.html`),
        chromedp.evaluateasdevtools(`document.documentelement.scrollwidth`, &amp;width),
        chromedp.emulateviewport(width, 10),
        chromedp.evaluateasdevtools(`document.documentelement.scrollheight`, &amp;height),
        chromedp.emulateviewport(width, height),
        chromedp.fullscreenshot(&amp;b, 100),
    )
    if err != nil {
        log.fatal(err)
    }
    err = ioutil.writefile(&quot;test.png&quot;, b, 0777)
    if err != nil {
        log.fatal(err)
    }

}

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&lt;!DOCTYPE html&gt;
&lt;head&gt;
&lt;meta charset=&quot;utf-8&quot;&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;div id=&quot;main&quot;&gt;
# 123
123
$\sin(x)=\sum_{n=0}^{\infty} \frac{(-1)^n}{(2n+1)!}x^{2n+1} \sin(x)=\sum_{n=0}^{\infty} \frac{(-1)^n}{(2n+1)!}x^{2n+1} \sin(x)=\sum_{n=0}^{\infty} \frac{(-1)^n}{(2n+1)!}x^{2n+1} \sin(x)=\sum_{n=0}^{\infty} \frac{(-1)^n}{(2n+1)!}x^{2n+1}$
&lt;/div&gt;

&lt;script src=&quot;https://cdn.jsdelivr.net/npm/[email&#160;protected]/dist/markdown-it-latex2img.min.js&quot;
    crossorigin=&quot;anonymous&quot;&gt;&lt;/script&gt;
&lt;script src=&quot;https://cdn.jsdelivr.net/npm/[email&#160;protected]/dist/markdown-it.min.js&quot;
    crossorigin=&quot;anonymous&quot;&gt;&lt;/script&gt;
&lt;script&gt;
    var main = document.getElementById(&quot;main&quot;);
    var md = window.markdownit({ html: true });
    md.use(window.markdownitLatex2img, { style: &quot;filter: opacity(75%);transform:scale(0.75);text-align:center&quot; });
    var result = md.render(main.innerHTML);
    main.innerHTML = result;
&lt;/script&gt;
&lt;/body&gt;

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I thought maybe there was a dpi setting? Or is it because my machine is too weak? Unfortunately, I don't have any more resources to explore the truth. So please help me, how can I make the screenshot clearer?

Solution

It has nothing to do with the configuration of your machine. Increasing devicescalefactor will make the image look better. See demo below:

package main

import (
    &quot;context&quot;
    &quot;log&quot;
    &quot;os&quot;

    &quot;github.com/chromedp/cdproto/emulation&quot;
    &quot;github.com/chromedp/chromedp&quot;
)

func main() {
    ctx, cancel := chromedp.newcontext(context.background(), chromedp.withdebugf(log.printf))
    defer cancel()

    var width, height int64
    var b []byte
    err := chromedp.run(ctx,
        chromedp.emulateviewport(10, 10),
        chromedp.navigate(`the content of the file is in the code block below.html`),
        chromedp.evaluateasdevtools(`document.documentelement.scrollwidth`, &amp;width),
        chromedp.actionfunc(func(ctx context.context) error {
            return chromedp.emulateviewport(width, 10).do(ctx)
        }),
        chromedp.evaluateasdevtools(`document.documentelement.scrollheight`, &amp;height),
        chromedp.actionfunc(func(ctx context.context) error {
            return chromedp.emulateviewport(width, height, func(sdmop *emulation.setdevicemetricsoverrideparams, steep *emulation.settouchemulationenabledparams) {
                sdmop.devicescalefactor = 3
            }).do(ctx)
        }),
        chromedp.fullscreenshot(&amp;b, 100),
    )
    if err != nil {
        log.fatal(err)
    }
    err = os.writefile(&quot;test.png&quot;, b, 0o777)
    if err != nil {
        log.fatal(err)
    }
}

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A larger devicescalefactor will produce a larger image:

$ file *.png
7e9rfcQO.png: PNG image data, 797 x 144, 8-bit/color RGBA, non-interlaced
test.png:     PNG image data, 2391 x 432, 8-bit/color RGBA, non-interlaced

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Other notes:

In your code, emulation.setdevicemetricsoverride(1920, 1080, 1.0, false).do(chromectx) returns a chromedp.errinvalidcontext error. It can be removed completely.
In your code, all calls to chromedp.emulateviewport are passed with the parameters width: 0 and height: 0. This should be wrapped in chromedp.actionfunc to get the updated width and height.

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