How to get size of base64 string in javascript

A question was posed today: can I get the exact length in bytes of the input data, if I have a Base64 string? Base64 encodes three bytes to four characters. Base64 is a way to encode binary data in ascii data. The goal is to make it easier to transfer. Putting binary data inside an xml file, for example, could act weird, but a Base64 string acts just like normal text. To encode, it splits up the three bytes into 4 6-bit numbers. A 6-bit number can represent 64 possible value. Each possible value corresponds to an ascii character.

To calculate the length of the original data, you must count how many sets of 4 characters are in the Base64 string. For each of those sets, you know you have 3 bytes of original data.

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This is almost correct, except: what if the length of the data doesn't nicely line up to a multitude of 3? Then you cannot get a nice set of four 6-bit numbers. The answer is yes. Substring characterCount - 2, 2. The input is a set of bytes: [10, 12, 13, 14] The output is an ascii string.

Base64 uses 4 ascii characters to encode bits 3 bytes of data. So four characters of base64 represent 3 bytes of data. In that case you need to add padding. At least it works. Share this.Base64 is a group of similar binary-to-text encoding schemes that represent binary data in an ASCII string format by translating it into a radix representation. Base64 encoding schemes are commonly used when there is a need to encode binary data that needs to be stored and transferred over media that are designed to deal with ASCII.

This is to ensure that the data remain intact without modification during transport. In JavaScript there are two functions respectively for decoding and encoding base64 strings:. The algorithm used by atob and btoa is specified in RFCsection 4. Note that btoa expects to be passed binary data, and will throw an exception if the given string contains any characters whose UTF representation occupies more than one byte. For more details, see the documentation for btoa. Each Base64 digit represents exactly 6 bits of data.

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Sign up now. Sign in with Github Sign in with Google.You can do this by first drawing the image to a canvas, which provides a method to directly get the image as data URL :. I was reading this. How would I do something like this using javascript where I can browse for the image, and then it turns it into a data uri string? Where you would browse for the image, then it would give you the data uri. IMHO, it would be better to write a desktop utility in Java.

how to get size of base64 string in javascript

Or another language, and maybe on a server. Just not JavaScript. Other than pure document size, this is the 1 factor concerning how fast a page loads. The browser having to download the base64 image code in with the JavaScript code, will delay the loading of the page because no scripting can occur until after the script as fully completed downloading.

If you want a solution to rapidly load images, load them in parallel using Ajax requests instead. Can someone separate the javascript into the javascript part, and the html into the html part. It crashed my tab when trying the first time. Is there a filesize limit?

I chose to do it on a 4 megabyte picture. Can this be made using javascript? Can this be made to do: mp3 to base64 data uri? And why someone would do that, I have no idea. Why not?

how to get size of base64 string in javascript

Is there a way I can use that? What would the code be to do that?By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Software Engineering Stack Exchange is a question and answer site for professionals, academics, and students working within the systems development life cycle. It only takes a minute to sign up. Right now I have a website that uploads an image as a base64 string to my server.

This string is converted back into a bitmap and resized. However, I would like the least amount of memory to be consumed in my server, therefore I would like to restrict the file size of the images being uploaded without processing them. Edit: apologies for blatantly wrong info. Acording to this Wikipedia articleit will be a bit larger:.

Very roughly, the final size of Baseencoded binary data is equal to 1. You can use ContentLength property of the request to determine what the size is in bytes, although if you are uploading more then one image, it might be trickier. You can read the algorithm here Base 64 wiki. Sign up to join this community.

The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Know file size with a base64 string Ask Question. Asked 4 years, 9 months ago. Active 1 year, 2 months ago. Viewed 25k times. I do not have very clear what a base64 string is or how it is related to a file. Is there a way to know the file of a size without actually saving the file into an stream?

Luis Becerril Luis Becerril 1 1 gold badge 1 1 silver badge 3 3 bronze badges. Active Oldest Votes. Acording to this Wikipedia articleit will be a bit larger: Very roughly, the final size of Baseencoded binary data is equal to 1. Alexus Alexus 2, 11 11 silver badges 21 21 bronze badges. Harish Moyal Harish Moyal 71 1 1 silver badge 1 1 bronze badge. The Overflow Blog. Socializing with co-workers while social distancing.

Podcast Programming tutorials can be a real drag. Featured on Meta. Community and Moderator guidelines for escalating issues via new responseā€¦. Feedback on Q2 Community Roadmap. Related 0. Hot Network Questions. Question feed.Base64 is a group of similar binary-to-text encoding schemes that represent binary data in an ASCII string format by translating it into a radix representation.

Above is a technical definition of Base64 from Wikipedia. Let us take a scenario where a user is allowed to upload an image file in a web application. Now, we would like to add a file size limit that can be uploaded. So, we need to add a server-side validation. The stack that you use on server is not important in this case as this is a general topic, so, consider the concept and not the syntax of the code added to this post.

The first most important task is to ensure that the encoded string that we have received from the client is properly formed, i. You may have a method out of the box in your stack that can validate this. The second way you may think to do is to convert that string to bytes and get the length from it just to know the size. So, now the question is ā€” how can we calculate the size without even converting it to bytes? To understand the answer, I recommend you to read Base64 Wikiif you have time.

Let me explain you the algorithm above. The result from formula above also includes padding information. To get the actual n bytes without padding:. The padding is added to the string so as to make the encoded output a multiple of 4 characters.

Now, the result can be used for validation. For our example, we can now use result, that is length in bytes for validation. Net ASP.

How to Encode and Decode Strings with Base64 in JavaScript

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How to test Pipes in Angular? Software Design Patterns. Introduction to Dependency Inversion Principle. A beginners guide to Dependency Injection. How to upload any file to Azure Blob storage service? When to use Dependency Inversion Principle in application? How to calculate the size of a base64 encoded string? Scenario to calculate the size of a base64 encoded string Let us take a scenario where a user is allowed to upload an image file in a web application.

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Forum Sencha Touch 2. Results 1 to 3 of 3. Thread: Calculating image size based on its encode64 string. Thread Tools Show Printable Version. Answered: Calculating image size based on its encode64 string Hi all. I have a Sencha Touch app which I already packaged as an native app. I'm using the Camera native API in order to take images from camera or library, both of them and then send them to my server and store them there.

I want to validate the image size before to send it to the server side, but I'm kind of lost about how to calculate the original image size based on the encode64 string that the API returns me. Take a look at this piece of code: Code:. Best Answer Posted by mitchellsimoens. The length of the base64 string won't be the size of the image.

how to get size of base64 string in javascript

You need to decode the string so you get the binary using the window. Thank you very much Mitchell. It seems the atob method is exactly what I was looking for. Quick Navigation Sencha Touch 2. Direct Ext: 4. All times are GMT The time now is PM. All rights reserved. Stay Connected Join our mailing list Subscribe.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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how to get size of base64 string in javascript

Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I was unable to mark this post as duplicate as of this post exist on other stackexchange so wrote an answer here just as a wiki.

Learn more. How to get image File size from base 64 string in javascript? Asked 1 year, 5 months ago. Active 1 year, 5 months ago. Viewed 3k times. I have base64 data for the image. Mukund Kumar. Mukund Kumar Mukund Kumar File size or image dimensions?

If you want file size then: stackoverflow. Please read the question description first then mark it duplicate. Your question is a dupe anyway Also, you edited your question to say "file size" when it was originally just "size" and marked a dupe. Active Oldest Votes. Bhojendra Rauniyar. The Overflow Blog. Socializing with co-workers while social distancing. Podcast Programming tutorials can be a real drag.

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