Javascript 无法在画布上绘制矩形
我正在用白色背景色在画布上画一幅图像。我想在图像上画一个边框,但我无法这样做。这是我的密码:Javascript 无法在画布上绘制矩形,javascript,html,canvas,Javascript,Html,Canvas,我正在用白色背景色在画布上画一幅图像。我想在图像上画一个边框,但我无法这样做。这是我的密码: var canvas = parent.document.createElement('canvas'); canvas.width = image.width; canvas.height = image.height; var context = canvas.getContext('2d'); context.fillStyle = "black"; context.font = "50px Ar
var canvas = parent.document.createElement('canvas');
canvas.width = image.width;
canvas.height = image.height;
var context = canvas.getContext('2d');
context.fillStyle = "black";
context.font = "50px Arial";
//context.fillText(chartId, canvas.width-200, 50);
context.drawImage(image, 0, 0);
context.fillStyle = "#000000";
context.rect(0,0,canvas.width,canvas.height);
context.globalCompositeOperation = "destination-over";
context.fillStyle = "#FFFFFF";
但是我下载这张图片时没有看到任何边框。你忘了画你的直肠
context.stroke();
看起来,您没有执行
context.stroke()
操作?缺少两件事
context.stroke()代码>绘制矩形后
context.beginPath()开始绘制rect()
代码>。这是为了避免下一个笔划也影响您绘制的第一个矩形
canvas.width = image.width;
canvas.height = image.height;
var context = canvas.getContext('2d');
context.fillStyle = "black";
context.font = "50px Arial";
//context.fillText(chartId, canvas.width-200, 50);
context.drawImage(image, 0, 0);
context.fillStyle = "#000000";
context.beginPath();
context.rect(0,0,canvas.width,canvas.height);
context.stroke();
context.globalCompositeOperation = "destination-over";
context.fillStyle = "#FFFFFF";