最近，我偶然發(fā)現(xiàn)了一個(gè)我無(wú)法克服的問(wèn)題。 我試圖在網(wǎng)站上編碼一個(gè)固定大小的畫布(400px x 400px ),但假設(shè)這個(gè)畫布有784像素(28px x 28px ),這樣我可以稍后將其轉(zhuǎn)換為numpy大小的數(shù)組(1，784)。 我試圖通過(guò)改變css、js或html中畫布的大小來(lái)做到這一點(diǎn)。目前我所知道的是，css只對(duì)& quot真實(shí)& quot畫布的大小，所以我希望我需要與js代碼的東西。

這是我的代碼

HTML:

<div class="field">
   <canvas id="canvas" width="28" height="28" ></canvas>
</div>

JS:

const canvas = document.getElementById("canvas");

canvas.width  = 400;
canvas.height = 400;
let context = canvas.getContext("2d");
context.fillStyle = "white";
context.fillRect(0,0,400,400);
console.log(canvas.clientHeight)
let draw_color = "black";
let draw_width = "14";
let is_drawing = false;
let start_background_color = "white";


canvas.addEventListener("touchstart",start,false);
canvas.addEventListener("touchmove",draw,false);
canvas.addEventListener("mousedown",start,false);
canvas.addEventListener("mousemove",draw,false);

canvas.addEventListener("touchend",stop,false);
canvas.addEventListener("mouseup",stop,false);
canvas.addEventListener("mouseout",stop,false);

function start(event){
    is_drawing = true;
    context.beginPath();
    context.moveTo(event.clientX - canvas.offsetLeft,
                    event.clientY-canvas.offsetTop);
    event.preventDefault();
}

function draw(event){
    if(is_drawing){
        context.lineTo(event.clientX - canvas.offsetLeft,
                        event.clientY-canvas.offsetTop)
        context.strokeStyle = draw_color;
        context.lineWidth = draw_width;
        context.lineCap = "round";
        context.lineJoin = "round";
        context.stroke();

    }
    event.preventDefault();
}

function stop(event){
    if(is_drawing){
        context.stroke();
        context.closePath();
        is_drawing=false;
    }
    event.preventDefault();
}

CSS:

#canvas{
    border:10px red;
    cursor: pointer;
    padding-left: 0;
    padding-right: 0;
    margin-left: auto;
    margin-right: auto;
    display: block;
    margin-top: 100px;
    margin-bottom: 0px;
}
.field{
  padding: 10px 10px 10px 10px;
  border: 10px red;

帆布照片