HTML to Image in Golang

This page describes how to convert web pages and HTML to images in Golang using the cloud-based Pdfcrowd API. The API is easy to use and it takes only a few of lines of code to integrate it to your application. You can find general information about the converter on the HTML to Image API page.

Installation

The Golang API client library provides easy access to the Pdfcrowd API. No third-party libraries are required.

Install the client library from Github
go get github.com/pdfcrowd/pdfcrowd-go

We also offer other installation options.

Authentication

The credentials to access the API are your Pdfcrowd username and the API key. You can try out the API without registering using the following demo credentials:

  • Username: demo
  • API key: ce544b6ea52a5621fb9d55f8b542d14d

To get your personal API credentials, you can start a free API trial or buy the API license.

Getting Started

You can enter a web page or upload an HTML file to get an image output preview in our API playground. The playground allows you to interactively play with the API settings and autogenerates corresponding Golang code that you can copy and paste to your application.

Or you can choose from the examples below and adapt the code to your needs.

API Method Reference

Refer to the HTML to Image Golang Reference for a description of all API methods.

Code Examples

Here are a few Golang examples to get you started quickly with the API. See more examples. 

package main

import (
    "os"
    "fmt"
    "github.com/pdfcrowd/pdfcrowd-go"
)

func main() {
    // create the API client instance
    client := pdfcrowd.NewHtmlToImageClient("demo", "ce544b6ea52a5621fb9d55f8b542d14d")

    // configure the conversion
    client.SetOutputFormat("png")

    // run the conversion and write the result to a file
    err := client.ConvertUrlToFile("http://www.example.com", "example.png")

    // check for the conversion error
    handleError(err)
}

func handleError(err error) {
    if err != nil {
        // report the error
        why, ok := err.(pdfcrowd.Error)
        if ok {
            os.Stderr.WriteString(fmt.Sprintf("Pdfcrowd Error: %s\n", why))
        } else {
            os.Stderr.WriteString(fmt.Sprintf("Generic Error: %s\n", err))
        }

        // rethrow or handle the exception
        panic(err.Error())
    }
}
package main

import (
    "os"
    "fmt"
    "github.com/pdfcrowd/pdfcrowd-go"
)

func main() {
    // create the API client instance
    client := pdfcrowd.NewHtmlToImageClient("demo", "ce544b6ea52a5621fb9d55f8b542d14d")

    // configure the conversion
    client.SetOutputFormat("png")

    // run the conversion and write the result to a file
    err := client.ConvertFileToFile("/path/to/MyLayout.html", "MyLayout.png")

    // check for the conversion error
    handleError(err)
}

func handleError(err error) {
    if err != nil {
        // report the error
        why, ok := err.(pdfcrowd.Error)
        if ok {
            os.Stderr.WriteString(fmt.Sprintf("Pdfcrowd Error: %s\n", why))
        } else {
            os.Stderr.WriteString(fmt.Sprintf("Generic Error: %s\n", err))
        }

        // rethrow or handle the exception
        panic(err.Error())
    }
}
package main

import (
    "os"
    "fmt"
    "github.com/pdfcrowd/pdfcrowd-go"
)

func main() {
    // create the API client instance
    client := pdfcrowd.NewHtmlToImageClient("demo", "ce544b6ea52a5621fb9d55f8b542d14d")

    // configure the conversion
    client.SetOutputFormat("png")

    // run the conversion and write the result to a file
    err := client.ConvertStringToFile("<html><body><h1>Hello World!</h1></body></html>", "HelloWorld.png")

    // check for the conversion error
    handleError(err)
}

func handleError(err error) {
    if err != nil {
        // report the error
        why, ok := err.(pdfcrowd.Error)
        if ok {
            os.Stderr.WriteString(fmt.Sprintf("Pdfcrowd Error: %s\n", why))
        } else {
            os.Stderr.WriteString(fmt.Sprintf("Generic Error: %s\n", err))
        }

        // rethrow or handle the exception
        panic(err.Error())
    }
}

API Playground Examples

The API can be easily integrated into your environment. You can have our interactive API Playground autogenerate the integration code for you:

Common Customizations

The API lets you convert a web page, a local HTML file, or a string containing HTML. The result of the conversion can be stored to a local file, to a stream object or to a variable. See the conversion input section for more details.

The best way to start with the API is to choose one of the examples and once you get it working, you can further customize the code. You can find the most common customizations in the table below.

Image size Set image dimensions with setScreenshotWidth and setScreenshotHeight.
Image format Specify a different output image format with setOutputFormat.
Hide or remove elements You can use the following classes in your HTML code to hide or remove elements from the output:
  • pdfcrowd-remove - sets display:none!important on the element
  • pdfcrowd-hide - sets visibility:hidden!important on the element
Learn about other options.
Use @media print You can switch to the print version of the page (if it exists) with setUsePrintMedia.
Run custom JavaScript You can use setOnLoadJavascript or setCustomJavascript to alter the HTML contents with a custom JavaScript. In addition to the standard browser APIs, the custom JavaScript code can use helper functions from our JavaScript library .
Custom CSS styling You can alter CSS styling used during conversion with a custom JavaScript or using the pdfcrowd-body CSS class, which is automatically set on the HTML <body> element. You can, for example, set the H1 height to 48px by adding the following line to your CSS:
.pdfcrowd-body h1 { font-size: 48px; }

Template Rendering

The API enables rendering of HTML templates. The template syntax is based on the Jinja template rendering engine.

The most common constructs are:

  • Data rendering: Invoice: {{ invoice.number }}
  • For loop: {% for invoice in invoices %} ... {% endfor %}
  • If statement: {% if invoice.total > 100 %} ... {% endif %}
  • Data filter: {{ invoice.to.first_name|capitalize }}

The supported input data formats are JSON, XML, CSV and YAML. The data can be uploaded from a file or from a string variable.

Supported template filters: capitalize, center, default, escape, first, forceescape, format, indent, join, last, length, list, lower, replace, reverse, safe, slice, sort, string, striptags, title, trim, truncate, unique, upper, wordcount, wordwrap.

See template rendering examples.

Error Handling

It is recommended that you implement error handling to catch errors that the API may return, see the example code below. A list of status codes and their description can be found here. 

// call the API 

    // print error
    os.Stderr.WriteString(fmt.Sprintf("Pdfcrowd Error: %s\n", why))

    // print just error code
    os.Stderr.WriteString(fmt.Sprintf("Pdfcrowd Error Code: %v\n", why.getCode()))

    // print just error message
    os.Stderr.WriteString(fmt.Sprintf("Pdfcrowd Error Message: %v\n", why.getMessage()))

    // or handle the error in your way

Troubleshooting

  • Refer to the API Status Codes page if the API returns an error.
  • You can use setDebugLog and getDebugLogUrl to get detailed info about the conversion, such as load errors, load times, browser console output, etc.
  • Check the FAQ.
  • You can use our JavaScript library to resolve rendering problems, such as missing content or blank pages.
    Just use setCustomJavascript with libPdfcrowd.highlightHtmlElements method call to visualize all HTML elements. See the backgrounds example , borders example and helper JavaScript library documentation.
  • The maximum size of the created image is 65 megapixels. Larger images are cropped vertically.
  • Contact us if you need help or missing a feature.