Download Image Base64 Javascript
Suzy Mcintire
The example code works for URL HTML images, but not inline base64 images, so I was wondering if there was a way to directly upload the base64 images to Ghost, rather than save them as a file, upload them to ghost, and then delete them!
Is there a way to convert the s3 image URL to base64 in nodejs? I need to send an email with the user profile. S3 link expires within a week. So, I need to convert the s3 image URL to base64. This is My code so far. But this is not working.
So I have an html.Img component in my Dash app that displays an image based on user input. Since some precomputation is required for the initial image to be created, it is saved as a local file temporarily to encode into a base64 string readable by the html.Img component:
I want to provide the option for the user to download any of these images at any time using a button and the dcc.Download() option. How would I go about recreating the PNG file from the base64 string to be sent to the dcc.Download for the user to download the image onto their system?
JavaScript has a convention for converting an image URL or a local PC image to a base64 string. This string can contain a variety of symbols and letters. In here it is explained how to make a canvas element, load an image into it, and use toDataURL to display the string representation. To obtain the base64 string representation, we will also use the file reader option.
In this case, it is created as a canvas element and its dimensions will be specified. The dataURL where the string representation will be stored. We will add random images from online sources and ensure the object to avoid security issues. 'Anonymous' as crossOrigin Finally, our callback function will pass the dataURL to the toDataURL function to notify the window that the base64 string for the corresponding image is ready for preview.
The data URI scheme is a uniform resource identifier (URI) scheme that provides a way to include data in-line in Web pages as if they were external resources. It is a form of file literal or here document. This technique allows normally separate elements such as images and style sheets to be fetched in a single Hypertext Transfer Protocol (HTTP) request, which may be more efficient than multiple HTTP requests,[1] and used by several browser extensions to package images as well as other multimedia content in a single HTML file for page saving.[2][3] As of 2022[update], data URIs are fully supported by most major browsers, and partially supported in Internet Explorer.[4]
Thus, within the overall URI syntax, a data URI consists of a scheme and a path, with no authority part, query string, or fragment. The optional media type, the optional base64 indicator, and the data are all parts of theURI path.
In this example, the image data is encoded with utf8 and hence the image data can broken into multiple lines for easy reading. Single quote has to be used in the SVG data as double quote is used for encapsulating the image source.
In this post, I want to address why in this day and age, this is almost always a very bad idea that has been carried over from years ago. Back then, web browsers had heavy limits on the number of concurrent connections they could send to the server. This meant an image heavy website would need to queue up requests and wait for the ones before to finish. Base64 provided a way of working around that by using an already open HTTP connection to deliver images embedded directly into the HTML or CSS. This effectively removed the need for an extra roundtrip the browser would need for each of the files.
To get to the answer why, we first need to establish what Base64 actually is. To put it simply, Base64 is an encoding schema used for representing binary data in a text format. This is useful when the storage or delivery medium does not support binary data such as when embedding an image into a database, CSS files or HTML. One must be careful to not mix up compression with encoding. While compression actually compresses data, encoding just defines a way how data is encoded, which brings us to the first issue.
When delivering images in Base64, the browser first needs to decode the Base64 encoded strings and then decode the images as well, which introduces an extra layer of unnecessary work. Base64 is very efficient, but count in the GZip or Brotli processing time that happens on the server to compress the response and the milliseconds quickly start adding up.
The third issue is perhaps the biggest performance killer, but perhaps not the most obvious at first glance. When a user accesses your website, the browser will automatically cache the images locally and then load them directly from your disk when visiting the same page again. Due to how Base64 works, the browser is unable to store the images locally so it will always need to fetch them from your server or CDN which creates extra load on your server as well as increases your bandwidth bill.
Another issue here is that if your images are embedded in your HTML code, content delivery networks such as BunnyCDN are not able to cache the files and they will always be returned from your origin server which might be thousands of kilometers away.
The reason for this is that sharing Base64 images is much harder due to the fact that they are not actually accessible via a public URL. This means that web crawlers and your users are unable to get links pointing back to your website, which makes sharing content much harder and can potentially hurt your "page rank" as well.
One such example would be very small images, where the Base64 string is actually smaller than the length of an URL string and HTTP request overhead when linking to an image file. Take for example a 1x1 pixel transparent PNG. Despite the original image being only 68 bytes in size, factoring in the HTTP headers etc, it actually ends up being bigger than the Base64 encoded string:
Although Chart.js was built for the frontend, it can be used in Node to generate Chart.js images thanks to several open-source projects. The most popular projects used for this purpose are ChartJsNodeCanvas and chartjs-node.
For instance email servers expect textual data, so ASCII is typically used. Therefore, if you want to send images or any other binary file to an email server you first need to encode it in text-based format, preferably ASCII. This is where Base64 encoding comes extremely handy in converting binary data to the correct formats.
In the above script we create a new buffer object and pass it our string that we want to convert to Base64. We then call the toString method on the buffer object that we just created and pass it "base64" as a parameter. The toString method with "base64" as parameter will return data in the form of Base64 string. Run the above code, you shall see the following output.
Decoding a Base64 string is quite similar to encoding it. You have to create a new buffer object and pass two parameters to its constructor. The first parameter is the data in Base64 and the second parameter is "base64". Then you simply have to call toString on the buffer object but this time the parameter passed to the method will be "ascii" because this is the data type that you want your Base64 data to convert to. Take a look at the following code snippet for reference.
As mentioned in the beginning of the article, the primary purpose of Base64 encoding is to convert binary data into textual format. Let us see an example where we will convert an image (binary data) into a Base64 string. Take a look at the following example.
Here you can see that we start with the Base64 data (which could've also been received from a socket or some other communication line) and we load it into a Buffer object. When creating the buffer we tell it that it's in base64 format, which allows the buffer to parse it accordingly for internal storage.
Base64 encoding is one of the most common ways of converting binary data into plain ASCII text. It is a very useful format for communicating between one or more systems that cannot easily handle binary data, like images in HTML markup or web requests.
A basic drive to convert a base64 string to an image might not agitate you like it would have been in the case of a reverse task. Most likely, you will not require to deal with the server-side for conversion.
After converting the base64 string, the image will be previewed in the web browser along with the dimensions as we have added the HTML DOM properties to manage to get the values. This is the minimalistic drive to get the job done.
It's not a good idea when you want your images and style information to be cached separately. Also if you encode a large image or a significant number of images in to your css file it will take the browser longer to download the file leaving your site without any of the style information until the download completes. For small images that you don't intend on changing often if ever it is a fine solution.
But it doesn't show up - not on the iPhone, nor two different versions of Outlook. The image is simply broken. We want to stick with base64 due to it already working with the web page and the ability to view an image if the user is offline.
An alternative approach may be to embed images in the email using the cid method. (Basically including the image as an attachment, and then embedding it). In my experience, this approach seems to be well supported these days.
760c119bf3