Algorithm to create a bitmap/canvas image from binary 1's and 0's to visually see the data in JavaScript?
Question
Let's say I have 20,164 binary digits in a standard JavaScript string, for example:
var data = '101010101010101010101010100110001011010101101' ...
What I want to do is see a visual representation of these digits by converting it to a bitmap or perhaps HTML5 canvas image. So if I loop through all the bits and it comes across a 1 it will draw a black pixel, and a 0 the pixel will be white.
So I'm guessing I'll need a 142 x 142 pixel grid something which looks like this:
What's an algorithm or way to do this in JavaScript? All I need to do is display it on the web page so maybe creating a basic bitmap or canvas or SVG image will be fine.
Many thanks
3 answers
solution1
7 ACCPTED 2013-07-10 22:07:23
You're exactly correct with the HTML5 canvas idea. You could try something like the following if you don't want to do base64 data.
Javascript (with no error checking):
var string = "1010101...";
var ctx = document.getElementById("canvas").getContext('2d');
ctx.fillStyle = "#FFF"; // Fill with white first
ctx.fillRect(0, 0, 142, 142);
ctx.fillStyle = "#000";
for (var i = 0; i < 142; i++) { // Loop through each character
for (var j = 0; j < 142; j++) {
if (string[i*142+j] == '1') // If the character is one,
ctx.fillRect(i, j, 1, 1 ); // fill the pixel with black
}
}
HTML:
<body>
<canvas width=142 height=142 id="canvas"></canvas>
</body>
If you use this, you should make sure to check that the length of the string is the length you are expecting.
solution2
5 2013-07-10 22:03:37
you can do something like
var canvas = document.getElementById("c");
var ctx = canvas.getContext("2d");
var image = new Image();
image.src ="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAIAAAACDbGyAAAAAXNSR0IArs4c6QAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9oMCRUiMrIBQVkAAAAZdEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIEdJTVBXgQ4XAAAADElEQVQI12NgoC4AAABQAAEiE+h1AAAAAElFTkSuQmCC";
image.onload = function() {
ctx.drawImage(image, 0, 0);
};
solution3
2 2013-07-10 22:13:24
You may also include the image directly in the HTML without using JS:
Example:
<img alt='' src='data:image/gif;base64,R0lGODlhBgASALMAAOfn5+rq6uvr6+zs7O7u7vHx8fPz8/b29vj4+P39/f///wAAAAAAAAAAAAAAAAAAACwAAAAABgASAAAIMAAVCBxIsKDBgwgTDkzAsKGAhxARSJx4oKJFAxgzFtjIkYDHjwNCigxAsiSAkygDAgA7'/>
But the image must be in a correct format: jpg, tiff, png, etc. not just as a bitmap. You may easily convert a bitmap to formats like BMP.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.