Convert HTML to Raster Image

EVO PDF Client for .NET Core

EVO HTML to PDF Converter also allows you to easily convert in just a few lines of code HTML pages and HTML strings to raster images in PNG, JPG or BMP format. In this section you can learn about the basic settings of the converter.

You can choose the HTML document to convert which can be:

A HTML page from a given URL. The URL must be accessible from the computer where the converter runs. If the page requires authentication or if you are using a proxy server to access Internet then you have to set the converter properties accordingly as described in documentation. The method you can use in this case is HtmlToImageConverterConvertUrlToImageTiles(String, ImageType)
A HTML string. When you convert a HTML string you also have the option to specify a base URL that will be used by converter to resolve the relative URLs found in the HTML string to fully qualified URLs. If your HTML string uses only fully qualified URLs then this parameter is not necessary The method you can use in this case is HtmlToImageConverterConvertHtmlToImageTiles(String, String, ImageType)

The basic options you can set are grouped in a few categories.

HTML Viewer Options

HTML Viewer Width. This option is the equivalent in converter of the browser window width. The property you can set in your code to control the browser window width is HtmlToImageConverterHtmlViewerWidth. When the browser window width is changed the HTML content displayed inside the window can have a different layout and something similar happens when you change the HTML Viewer width of the converter. At a given viewer width, the converter will capture by default the whole height of the HTML content, but you can set the HTML Viewer height to capture only the top part of the HTML page
HTML Viewer Height. This option is the equivalent in converter of the browser window height and can be used to limit the conversion to the top part of the HTML page. If this property is not set the entire page will be converted. The property you can set in your code to control the browser window height is HtmlToImageConverterHtmlViewerHeight

Image Options

Image Format. This option allows you select the output image format. You can choose between PNG, JPG and BMP. You can choose the image frmat when you save an image tile of System.DrawingImage type to a file or stream
Transparent Background. This option allows you choose if the image background is transparent or not. This option has effect only when you save the image tile of System.DrawingImage type to PNG image. The property you can set in your code to background transparency is HtmlToImageConverterTransparentBackground

Navigation Options

Navigation Timeout. This option represents the maximum time to wait for a web page to be loaded by converter. If the web page cannot be loaded in this time interval the converter will throw an exception. The property you can set in your code for this option is HtmlToImageConverterNavigationTimeout.
Delay Conversion. This option represents an additional time to wait after the HTML page was loaded to allow the asynchronous operations to finish before starting to capture the HTML content. If you cannot estimate the additional time to wait then you have the option to manually trigger the conversion. The property you can set in your code for this option is HtmlToImageConverterConversionDelay.

Code Sample - Convert HTML to Raster Image

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Http;

// Use EVO PDF Namespace
using EvoPdfClient;

namespace EvoHtmlToPdfDemo.Controllers.HTML_to_PDF.HTML_to_Image
{
    public class Convert_HTML_to_ImageController : Controller
    {
        [HttpPost]
        public ActionResult ConvertHtmlToImage(IFormCollection collection)
        {
            // Get the server options
            string serverIP = collection["textBoxServerIP"];
            uint serverPort = uint.Parse(collection["textBoxServerPort"]);
            string servicePassword = collection["textBoxServicePassword"];
            bool useServicePassword = servicePassword.Length > 0;
            bool useTcpService = collection["ServerType"] == "radioButtonUseTcpService";
            string webServiceUrl = collection["textBoxWebServiceUrl"];

            // Create the HTML to Image converter object
            HtmlToImageConverter htmlToImageConverter = null;
            if (useTcpService)
                htmlToImageConverter = new HtmlToImageConverter(serverIP, serverPort);
            else
                htmlToImageConverter = new HtmlToImageConverter(true, webServiceUrl);

            // Set optional service password
            if (useServicePassword)
                htmlToImageConverter.ServicePassword = servicePassword;

            // Set license key received after purchase to use the converter in licensed mode
            // Leave it not set to use the converter in demo mode
            htmlToImageConverter.LicenseKey = "4W9+bn19bn5ue2B+bn1/YH98YHd3d3c=";

            // Set HTML Viewer width in pixels which is the equivalent in converter of the browser window width
            htmlToImageConverter.HtmlViewerWidth = int.Parse(collection["htmlViewerWidthTextBox"]);

            // Set HTML viewer height in pixels to convert the top part of a HTML page 
            // Leave it not set to convert the entire HTML
            if (collection["htmlViewerHeightTextBox"][0].Length > 0)
                htmlToImageConverter.HtmlViewerHeight = int.Parse(collection["htmlViewerHeightTextBox"]);

            // Set if the created image has a transparent background
            htmlToImageConverter.TransparentBackground = SelectedImageFormat(collection["imageFormatComboBox"]) == ImageType.Png ? collection["transparentBackgroundCheckBox"].Count > 0 : false;

            // Set the maximum time in seconds to wait for HTML page to be loaded 
            // Leave it not set for a default 60 seconds maximum wait time
            htmlToImageConverter.NavigationTimeout = int.Parse(collection["navigationTimeoutTextBox"]);

            // Set an adddional delay in seconds to wait for JavaScript or AJAX calls after page load completed
            // Set this property to 0 if you don't need to wait for such asynchcronous operations to finish
            if (collection["conversionDelayTextBox"][0].Length > 0)
                htmlToImageConverter.ConversionDelay = int.Parse(collection["conversionDelayTextBox"]);

            byte[][] imageTiles = null;

            if (collection["HtmlPageSource"] == "convertUrlRadioButton")
            {
                string url = collection["urlTextBox"];

                // Convert the HTML page given by an URL to a set of Image objects
                imageTiles = htmlToImageConverter.ConvertUrlToImageTiles(url, SelectedImageFormat(collection["imageFormatComboBox"]));
            }
            else
            {
                string htmlString = collection["htmlStringTextBox"];
                string baseUrl = collection["baseUrlTextBox"];

                // Convert a HTML string with a base URL to a set of Image objects
                imageTiles = htmlToImageConverter.ConvertHtmlToImageTiles(htmlString, baseUrl, SelectedImageFormat(collection["imageFormatComboBox"]));
            }

            // Save the first image tile to a memory buffer

            byte[] outImageBuffer = imageTiles[0];

            string imageFormatName = collection["imageFormatComboBox"][0].ToLower();

            // Send the image file to browser
            FileResult fileResult = new FileContentResult(outImageBuffer, "image/" + (imageFormatName == "jpg" ? "jpeg" : imageFormatName));
            fileResult.FileDownloadName = "HTML_to_Image." + imageFormatName;

            return fileResult;
        }

        private ImageType SelectedImageFormat(string selectedValue)
        {
            switch (selectedValue)
            {
                case "Png":
                    return ImageType.Png;
                case "Jpg":
                    return ImageType.Jpeg;
                case "Bmp":
                    return ImageType.Bmp;
                default:
                    return ImageType.Png;
            }
        }
    }
}