HTML to Image in Golang

This page describes how to convert web pages and HTML to images in Golang using the Pdfcrowd API. The API is easy to use and the integration takes only a few of lines of code.

Samples

Installation

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

We also offer other installation options.

Authentication

Authentication is needed in order to use the Pdfcrowd API. The credentials used for accessing the API are your Pdfcrowd username and the API key.

You can try out the API without registration 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

Enter a web page or upload an HTML file to get an image preview and integration 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. You can also interactively explore the API in the API Playground.

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 store the result into the "image" variable
    image, err := client.ConvertUrl("http://www.example.com")

    // check for the conversion error
    handleError(err)

    // at this point the "image" variable contains PNG raw data and
    // can be sent in an HTTP response, saved to a file, etc.
}

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")

    // create an output stream for the conversion result
    outputStream, err := os.Create("example.png")

    // check for a file creation error
    handleError(err)

    // close the output stream
    defer outputStream.Close()

    // run the conversion and write the result into the output stream
    err = client.ConvertUrlToStream("http://www.example.com", outputStream)

    // 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 store the result into the "image" variable
    image, err := client.ConvertFile("/path/to/MyLayout.html")

    // check for the conversion error
    handleError(err)

    // at this point the "image" variable contains PNG raw data and
    // can be sent in an HTTP response, saved to a file, etc.
}

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")

    // create an output stream for the conversion result
    outputStream, err := os.Create("MyLayout.png")

    // check for a file creation error
    handleError(err)

    // close the output stream
    defer outputStream.Close()

    // run the conversion and write the result into the output stream
    err = client.ConvertFileToStream("/path/to/MyLayout.html", outputStream)

    // 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())
    }
}
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 store the result into the "image" variable
    image, err := client.ConvertString("<html><body><h1>Hello World!</h1></body></html>")

    // check for the conversion error
    handleError(err)

    // at this point the "image" variable contains PNG raw data and
    // can be sent in an HTTP response, saved to a file, etc.
}

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")

    // create an output stream for the conversion result
    outputStream, err := os.Create("HelloWorld.png")

    // check for a file creation error
    handleError(err)

    // close the output stream
    defer outputStream.Close()

    // run the conversion and write the result into the output stream
    err = client.ConvertStringToStream("<html><body><h1>Hello World!</h1></body></html>", outputStream)

    // 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")
    client.SetDebugLog(true)

    // 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)
    
    // print URL to the debug log
    fmt.Println("Debug log url:", client.GetDebugLogUrl())
    
    // print the number of available conversion credits in your account
    fmt.Println("Remaining credit count:", client.GetRemainingCreditCount())
    
    // print the number of credits consumed by the conversion
    fmt.Println("Consumed credit count:", client.GetConsumedCreditCount())
    
    // print the unique ID of the conversion
    fmt.Println("Job id:", client.GetJobId())
    
    // print the size of the output in bytes
    fmt.Println("Output size:", client.GetOutputSize())
}

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())
    }
}

Integration 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.

Template Rendering Examples

package main

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

func main() {
    // create the API client instance
    client := pdfcrowd.NewHtmlToPdfClient("{{ user_name }}", "{{ api_key }}")

    // configure the conversion
    client.SetDataString(`{
            "name": "World",
            "product": "Pdfcrowd API"
        }`)

    // run the conversion and write the result to a file
    err := client.ConvertStringToFile("Hello {{ name }} from {{ product }}", "output.pdf")

    // 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.NewHtmlToPdfClient("{{ user_name }}", "{{ api_key }}")

    // configure the conversion
    client.SetDataString(`<?xml version="1.0" encoding="UTF-8"?>
        <data>
          <name>World</name>
          <product>Pdfcrowd API</product>
        </data>`)

    // run the conversion and write the result to a file
    err := client.ConvertStringToFile("Hello {{ data.name }} from {{ data.product }}", "output.pdf")

    // 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.NewHtmlToPdfClient("{{ user_name }}", "{{ api_key }}")

    // configure the conversion
    client.SetDataString(`name: World
product: Pdfcrowd API`)

    // run the conversion and write the result to a file
    err := client.ConvertStringToFile("Hello {{ name }} from {{ product }}", "output.pdf")

    // 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.NewHtmlToPdfClient("{{ user_name }}", "{{ api_key }}")

    // configure the conversion
    client.SetDataString(`name,product
World,Pdfcrowd API`)

    // run the conversion and write the result to a file
    err := client.ConvertStringToFile("Hello {{ name }} from {{ product }}", "output.pdf")

    // 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())
    }
}

Error Handling

// 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

API Method Reference

Refer for details to the API Method Reference.