无法下载HTML画布上的图像 [英] Image On HTML Canvas Can't Be Downloaded

问题描述

我有HTML画布，可以很好地显示图像.

I have HTML canvas and it work fine to display image.

我有这个jQuery代码来下载图像:

And I have this jquery code to download the image :

$(".img-download").click(function(){
    var data = canvas.toDataURL();
    download.href = data; -- I tried this to download image, but PNG file generated cannot be opened in photoshop or any other image manipulation apps
    alert (data); -- then, I tried to see what's actually the data content
});

这是我的下载按钮:

<a href="" class="img-download btn btn-lg btn-default" download="image.png">Download</a>

data的内容如下:

data:image/png;base64,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...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

为什么成功生成PNG文件，但为什么无法打开?为什么PNG文件已损坏?

why it generate PNG file successfully, but why it can't be opened? why the PNG file is corrupt?

更新:这是我完整的jquery脚本

UPDATE : here's my complete jquery script

    $(".pepe-thumbnail").click(function(){
        var pepe_src = $(this).attr("src");
        $("#canvasimg").attr("src", pepe_src);
    });

    var canvas = document.getElementById("canvas");
    ctx = canvas.getContext("2d");

    var deviceWidth = window.innerWidth;;

    canvasWidth = deviceWidth - 40;
    canvasHeight = deviceWidth - 40;

    canvas.width = canvasWidth;
    canvas.height = canvasHeight;

    if (canvas.width > 500 || canvas.height > 500){
        canvas.width = 560;
        canvas.height = 500;    
    }

    var img = document.getElementById("canvasimg");
    //imgx = canvas.width/2 - img.width/2;
    //imgy = canvas.height/2 - img.height/2;

    imgx = 0;
    imgy = 0;

    function runLoop(){             
        ctx.lineWidth  = 8;
        ctx.font = "26pt Lato";
        ctx.strokeStyle = "black";
        ctx.fillStyle = "white";
        ctx.textAlign = "center";
        ctx.lineJoin = "round";

        var text1 = document.getElementById("canvastext-top").value;
        //text1 = text1.toUpperCase();

        var text2 = document.getElementById("canvastext-bottom").value;
        //text2 = text2.toUpperCase();

        x = canvas.width/2;
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        ctx.drawImage(img, imgx, imgy, canvas.width, canvas.height);

        ctx.strokeText(text1, x, 50);
        ctx.fillText(text1, x, 50);

        ctx.strokeText(text2, x, (canvas.height - 40));
        ctx.fillText(text2, x, (canvas.height - 40));

        window.setTimeout(runLoop, 14);
    };
    runLoop();

    $(".img-download").click(function(){
        var data = canvas.toDataURL();
        alert (data);
    });

推荐答案

尝试一下:

$(".img-download").click(function(){
    var data = canvas.toDataURL();
    $(this).attr("href",data)
  $(this).attr("download","imgName.png");
}); 

参考:使用JS Jquery下载画布图像

这篇关于无法下载HTML画布上的图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！