Question

我可以将图像上传到浏览器并将其转换为BLOB。之后，我尝试将它绘制到我的画布中，但它没有得到识别。我有一种感觉，这是我想念的小东西，但我看不到它。任何帮助都会很棒！

var resize_img  = 
function(){

    var file = document.getElementById("add_img").files;

    // add in file type checker

    // Create img element to PREVIEW
    var img = document.createElement("img");
    img.src = window.URL.createObjectURL(file[0]);


    // Draw image to CANVAS
    var canvas_e = document.getElementById("canvas_img");
    var ctx = canvas_e.getContext("2d");
    ctx.drawImage(img, 0, 0);

    //Resize Image
    var MAX_WIDTH = 800;
    var MAX_HEIGHT = 600;
    var width = img.width;
    var height = img.height;

    if (width > height) {
    if (width > MAX_WIDTH) {
        height *= MAX_WIDTH / width;
        width = MAX_WIDTH;
    }
    } else {
    if (height > MAX_HEIGHT) {
        width *= MAX_HEIGHT / height;
        height = MAX_HEIGHT;
    }
    }
    canvas_e.width = width;
    canvas_e.height = height;
    ctx.drawImage(img, 0, 0, width, height);


    //Push Data
    var dataurl = canvas_e.toDataURL("image/png");
    console.log(dataurl);

}

HTML

<!DOCTYPE html>
<html>
    <head>
        <meta content="text/html;charset=utf-8" http-equiv="Content-Type">
    <meta content="utf-8" http-equiv="encoding">
    <!-- CSS -->
    <link href="css/main.css" rel="stylesheet" type="text/css" >
    </head>
    <body>  
      <input type="file" id="add_img" onchange="resize_img()">
      <canvas id="canvas_img"></canvas> 
      <!-- JS -->
      <script src="js/main.js" type="text/javascript"></script> 
    </body>
</html>

Answer 1

将画布代码放在img.onload = function（）{....}

中

Blob图像不使用javascript进入Canvas

1 个答案: