An example of how to blur images using JavaScript-JS Tutorial-php.cn

An example of how to blur images using JavaScript

高洛峰

Release： 2017-01-16 09:36:03

Original

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Preface

As we all know, a complete image is composed of three channels: red, green, and blue. Thumbnails for the red, green, and blue channels are all displayed in grayscale. Use different gray scales to represent the proportion of "red, green, and blue" in the image. The pure white in the channel represents the highest brightness of this color light here, and the brightness level is 255.

Fuzzy method:

is to take out the R (G, B) of a pixel and the R (G, B) of its surrounding pixels, and then average it. Assign R (G, B) to this pixel; this completes the blurring;

Example:

1 2 3

4 5 6

7 8 9

For example, for this pixel 5, combine 5 pixels and the surrounding 8 pixels (1,2,3, 4,6,7,8,9), take the average of these 9 points and assign it to the 5 pixel point

R(5) = (R1+ R2+R3+R4+R5+R6+R7+R8+R9)/9;

G(5) = (G1+G2+G3+G4+G5+G6+G7+G8+ G9)/9;

B(5) = (B1+B2+B3+B4+B5+B6+B7+B8+B9)/9;

Rendering:

An example of how to blur images using JavaScript

Example code

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>ImgBase</title>
        <style type="text/css">
            .scream{
                width:400px;
                height:300px;
                position: absolute;
                top:60px;
                border: 1px solid;
            }
            #canvas{
                position: absolute;
                top:60px;
                left:500px;
                border: 1px dashed;
            }
        </style>
    </head>
    <body>
        <input type="file" onchange="loadImg()"/>
        <input type="button" value="模糊化" onclick="Fuzzy()"/>
        <br/><br/>
        <div class="scream">
            <img id="scream" width="400px" height="300px" alt="Image preview...">
        </div>
        <canvas id="canvas" width="400px;" height="300px;">
            your browser does not support canvas!
        </canvas>
         
        <script>
            function Fuzzy(){
                var c=document.getElementById("canvas");
             var ctx=c.getContext("2d");
             var imgData=ctx.getImageData(0,0,c.width,c.height);
             var img_w = imgData.width;
             var img_h = imgData.height;
              
             for(var w=1;w<(img_w-1);w++){
                for(var h=1;h<(img_h-1);h++){
                    //起始点
                    var i = (w+img_w*h)*4;
                    var R = imgData.data[i-1604]+imgData.data[i-1600]+imgData.data[i-1596]+imgData.data[i-4]+imgData.data[i]
                    +imgData.data[i+4]+imgData.data[i+1596]+imgData.data[i+1600]+imgData.data[i+1604];  //R(0-255)
                    var G = imgData.data[i-1603]+imgData.data[i-1599]+imgData.data[i-1595]+imgData.data[i-3]+imgData.data[i+1]
                    +imgData.data[i+5]+imgData.data[i+1597]+imgData.data[i+1601]+imgData.data[i+1605];  //G(0-255)
                    var B = imgData.data[i-1602]+imgData.data[i-1598]+imgData.data[i-1594]+imgData.data[i-2]+imgData.data[i+2]
                    +imgData.data[i+6]+imgData.data[i+1598]+imgData.data[i+1602]+imgData.data[i+1606];; //G(0-255)
                    var Alpha = imgData.data[i+3];  //Alpha(0-255)
             
                    imgData.data[i] = R/9;
                  imgData.data[i+1] = G/9;  
                  imgData.data[i+2] = B/9;  
                  imgData.data[i+3] = Alpha;    
                }
             }
             ctx.putImageData(imgData,0,0);
            }
        </script>
        <script>
            //canvas图像的宽高 
            var c_w = 400; var c_h = 300;
            //加载img图像
            function loadImg(){
                var img = document.getElementById("scream");
                var file = document.querySelector(&#39;input[type=file]&#39;).files[0];
                if(!/image\/\w+/.test(file.type)){
              alert("文件必须为图片！");
              return false;
             }
                var reader = new FileReader();
                reader.addEventListener("load", function () {
                 img.src = reader.result;
                }, false);
                 
                if(file) {
                    reader.readAsDataURL(file);
                    loadCanvas();
                }
            }
            //加载canvas图像
            function loadCanvas(){
                var c=document.getElementById("canvas");
                var ctx=c.getContext("2d");
                 
                var img = document.getElementById("scream");
                img.onload = function() {
                    ctx.drawImage(img,0,0,c_w,c_h);
                } 
            }
        </script>
    </body>
</html>

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Summary

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For more examples of JavaScript methods to achieve image blurring, please pay attention to the PHP Chinese website!