I heard a lot about Baase64 Encoding for Images in Webdesign.
And i saw a lot of developers they use it for thier headlines with: data:image/png;base64,iVBORw0...
Is there any automatism (with javascript) behind?
Or have they all converted & inserted ? (could not belive)
Example: http://obox-inkdrop.tumblr.com/ (- Headlines)
First of all, the encoding has to be done on the server-side, be it :
automated with a script, that reads the original image file, and returns the base64 encoded string to inject it into the HTML that's being generated
or by hand, and directly placed into the HTML.
The base64 encoding cannot be done on the client-side, as the goal is to avoid sending the image file from the server to the browser (to minimize the number of HTTP requests).
Depending of the language that's used on the server-side, you'll probably find some function to do base64 encoding.
In PHP, you might be interested by base64_encode()
Related
I am new to XML. I have an XML document that I am inserting data manually. I wanted to know if it is possible to include an image in an XML file and not by using the file path. I have found something about encoding but I do not understand how this work and the option is not even available in the XML editor. After storing the images in the XML file, I will access it using javascript. Please provide further information on this matter.
An image is binary data, and the usual way to store binary data in an XML document is by encoding it in base64 (which turns it into ASCII characters). Libraries to convert from binary to base64, and back, are widely available, but the details depend very much on your programming environment. There are also online services where you can upload an image and get back its base64 representation: an example is here https://www.base64encode.net/base64-image-encoder
I am browsing the deck.gl repo. It ships with some examples with text files, for example this one. These files have a .txt extension, but aren't plain text:
!OohmwFjqwbMg#[?ADKJYXF#^?N?FAD
=wnmwFvvwbM_#WNg####C?C_#UA?AD#?Of#_#UTu#??BK?A??FUVP?#JF?AVP?#JF?AVPGTA?EL#?
=urmwF|swbM_#UFS##BK?C#C#A#E?CIGA?GE?CIGA#CF?#ABA#CJ##GR]Ud#wA\T?#DB?AXP?#DB?A\T
<aymwFnvwbMaAOKCA#OKPk#CCDKAADKAADKAADKAADKAAL_#fBjAIVCCEL
The examples also contain JavaScript files that look as though they are used to decode these files, for example this one for the file above.
What exactly is going on here? I assume this is a way of reducing the size of the data, but why not just rely on browser gzipping?
And why use a plain text extension when the file is clearly plain text? And why have a custom decoder at all?
It looks like a custom encoding that uses byte values to encode coordinates/GeoJSON features.
For example, this line from /dist-demo/data/building-data.txt:
!GqgmwFrhwbM}C}##K#IBO#IlBh#BOBMn#PHBGd#KC
is decoded using the decodePolyline() utility function into this array:
[
[0.00004,0.00001],
[40.70541,0.00002],
[40.7062,-74.01624],
[40.70619,-74.01593],
[40.70618,-74.01587],
[40.70616,-74.01582],
[40.70615,-74.01574],
[40.7056,-74.01569],
[40.70558,-74.0159],
[40.70556,-74.01582],
[40.70532,-74.01575],
[40.70527,-74.01584],
[40.70531,-74.01586],
[40.70537,-74.01605],
[40.70537,-74.01603]
]
which is substantially larger in JSON format.
So my guess would be that the main reason is to be able to use smaller data files that are still portable/cacheable. It's still line-based clear text, so it's diffable as well.
Also, these files are still compressible. I assume that a full JSON file is not only larger to begin with but also exhibits less favorable compression characteristics than this file. A quick test on building-data.txt shows a compression ratio of roughly 2:1 for gzip/deflate (139,089 bytes to 72,660 bytes compressed). The compression result for the same file in raw JSON won't be anywhere near that.
I have a REST service that returns a base64 representation of a file, could be any variety (assuming for now its application/pdf), and am wondering if there's a simple way to trigger the browser to save that base64 string into a file download that can be processed within JavaScript. I've looked at download.js but it doesn't seem to do what I intend it to do, unless its tied to a click event (something I really can't do here). Are there any other suggestions to implement this?
I have a simple PHP file which loads a file from my server, base64 encodes it and echoes it out.
Then I have a simple HTML page that uses jQuery to fetch this file, base64 decode it and do a checksum test. The checksum test is not working.
I md5'd the file in PHP after encoding it and md5'd it in javascript before decoding it and the checksums matched (So nothing went wrong during transit). However, the pre encoding and post decoding checksums do NOT match.
I am using webtoolkit.base64.js for decoding it in JavaScript. The file is a binary file (A ZIP archive).
Is there a problem with the decoding library or something else I'm not aware of that could cause this issue? Could it be a problem with the MD5 library I'm using (http://pajhome.org.uk/crypt/md5/md5.html)
Summary
Your MD5 library is OK, your base64 library is broken.
Both your JavaScript Base64 library and MD5 library are not working correctly.
I have created and verified a ZIP file of 15097 bytes.
MD5 sum: a9de6b8e5a9173140cb46d4b3b31b67c
I have base64-encoded this file: http://pastebin.com/2rfdTzYT (20132 bytes).
Verify the length of the base64 file at pastebin, using the following JavaScript snippet:
document.querySelector('.de1').textContent.replace(/\s/g,'').length;
Base64-decode the file properly using atob, and verify the size:
window.b64_str = document.querySelector('.de1').textContent.replace(/\s/g,'');
console.log( atob(window.b64_str).length ); /* 15097 */
I verified that both files were exactly equal using the Hexdump JavaScript library, and the xxd UNIX command (available as EXE file for Windows).
Using your Base64 decoder, I get a string with the size of 8094. That is not 15097!
During my tests, I discovered that the atob method returned incorrect bytes after certain byte sequences, including carriage returns. I have not yet found a solution to this.
Your MD5 library is OK.
I may be misunderstanding the question, but if I'm not I've run into something like this before. The javascript library you're using doesn't do binary. What php encodes is going to be a bunch of 1's and 0's but what the javascript spits out is going to be text. If you want a binary string you'll have to convert the resulting text to binary, then it should be the same as your original file.
I'll cut right to the chase. Right now I am developing a web based application. It has a PHP REST based architecture that serves up XML documents. On many of these documents attributes are hex encoded picture strings.
On the client side jQuery AJAX fetches an XML document with a picture in it. I need to display said picture in some <img> tags. However my knowledge on such methods is lacking so here I am asking for help.
Goal:
JavaScript String variable in hex or base64 >>> HTML displayed image.
Cross browser is required, or a hack for the ones that do not support it is fine.
Thanks,
Gunnar
Encode the images using base64 and write them out in a CDATA string into your XML with this format:
data:[<MIME-type>][;charset="<encoding>"][;base64],0123456789abcdefg...
When constructing your document, use this string as your src
<img src="data:image/png;base64,0123456789abcdefg..." />
Is it possible to use a php file just for rendering the image? That php file could write some base64 encoded values via
echo base64_decode($_GET['data']);
while you embed images like
<img src="http://host/yourPhpFileForDecode.php?data=base64encoded.../>