JS實現馬賽克圖片效果

吞石魚發表於2018-08-28
JS

整體邏輯：獲取oldImg圖片的畫素資訊，以5*5為單位，在5*5單位中取到一個隨機畫素並賦值給5*5中的所有畫素點，加以迴圈，以實現馬賽克效果。

<!DOCTYPE html>
<html>

    <head>
        <meta charset="UTF-8">
        <title></title>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
            }

            body {
                background-color: grey;
                text-align: center;
            }

            #myCanvas {
                background-color: rgba(250, 0, 0, 0.3);
            }
        </style>
    </head>

    <body>
        <canvas id="myCanvas" width="500" height="400"></canvas>
    </body>
    <script type="text/javascript">
        window.onload = function() {
            var myCanvas = document.getElementById('myCanvas');
            var painting = myCanvas.getContext('2d');
              //生成一個圖片節點
            var imgNode = new Image();
            imgNode.src = '1.jpg';
            //呼叫函式
            drawImg(imgNode);

            function drawImg(imgNode) {
                //圖片載入後執行馬賽克實現語句：5個一組取到隨機畫素賦給新圖裡的五個一組
                imgNode.onload = function() {
                    painting.drawImage(imgNode, 0, 0, 250, 400);

                    var size = 5;
                    //獲取老圖所有畫素點
                    var oldImg = painting.getImageData(0, 0, 250, 400)
                    //建立新影像素物件
                    var newImg = painting.createImageData(250, 400)

                    for(var i = 0; i < oldImg.width; i++) {
                        for(var j = 0; j < oldImg.height; j++) {
                            //從5*5中獲取單個畫素資訊
                            var color = getPxInfo(oldImg, Math.floor(i * size + Math.random() * size), Math.floor(j * size + Math.random() * size))

                            //寫入單個畫素資訊
                            for(var a = 0; a < size; a++) {
                                for(var b = 0; b < size; b++) {
                                    //                            (a,b)
                                    setPxInfo(newImg, i * size + a, j * size + b, color);
                                }
                            }

                        }

                    }
                    painting.putImageData(newImg, 250, 0)
                }
            }

            //讀取單個畫素資訊
            function getPxInfo(imgDate, x, y) {
                var colorArr = [];

                var width = imgDate.width;

                colorArr[0] = imgDate.data[(width * y + x) * 4 + 0]
                colorArr[1] = imgDate.data[(width * y + x) * 4 + 1]
                colorArr[2] = imgDate.data[(width * y + x) * 4 + 2]
                colorArr[3] = imgDate.data[(width * y + x) * 4 + 3]

                return colorArr;

            }

            //寫入單個畫素資訊
            function setPxInfo(imgDate, x, y, colors) {
                //（x,y） 之前有多少個畫素點  ==  width*y + x
                var width = imgDate.width;

                imgDate.data[(width * y + x) * 4 + 0] = colors[0];
                imgDate.data[(width * y + x) * 4 + 1] = colors[1];
                imgDate.data[(width * y + x) * 4 + 2] = colors[2];
                imgDate.data[(width * y + x) * 4 + 3] = colors[3];

            }

        }
    </script>

</html>

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