实现图片灰度效果
Created by Jerry Wang, last modified on Jul 31, 2014
[外鏈圖片轉存失敗(img-LKOoy4ic-1568514966835)(https://user-images.githubusercontent.com/5669954/27214416-9d938e3e-526c-11e7-8be6-8c372d53d2f3.png)]
2. 創建一個新的page ( with flow logic).
html code如下:
<%@page language="abap"%> <%@extension name="htmlb" prefix="htmlb"%> <html> <head> <script> window.onload = function() { var canvas = document.getElementById("myCanvas"); var image = document.getElementById("imageSource"); // re-size the canvas deminsion canvas.width = image.width; canvas.height = image.height; // get 2D render object var context = canvas.getContext("2d"); context.drawImage(image, 0, 0); var canvasData = context.getImageData(0, 0, canvas.width, canvas.height); alert(canvasData.width.toString()); alert(canvasData.height.toString()); // gray filter for ( var x = 0; x < canvasData.width; x++) { for ( var y = 0; y < canvasData.height; y++) { // Index of the pixel in the array var idx = (x + y * canvasData.width) * 4; var r = canvasData.data[idx + 0]; var g = canvasData.data[idx + 1]; var b = canvasData.data[idx + 2]; // calculate gray scale value var gray = .299 * r + .587 * g + .114 * b; // assign gray scale value canvasData.data[idx + 0] = gray; // Red channel canvasData.data[idx + 1] = gray; // Green channel canvasData.data[idx + 2] = gray; // Blue channel canvasData.data[idx + 3] = 255; // Alpha channel // add black border if(x < 8 || y < 8 || x > (canvasData.width - 8) || y > (canvasData.height - 8)) { canvasData.data[idx + 0] = 0; canvasData.data[idx + 1] = 0; canvasData.data[idx + 2] = 0; } } } context.putImageData(canvasData, 0, 0); // at coords 0,0 }; </script> </head> <body> <h2>Hello World!</h2> <img id="imageSource" src="map.png" alt="Canvas Source" /> <canvas id="myCanvas" >Gray Filter</canvas> </body> </html> 3. 測試效果如下: 代碼來自http://www.html5cn.org/article-5005-1.html要獲取更多Jerry的原創文章，請關注公眾號"汪子熙":
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