在画布上创建/绘制多个图像 html5.

Question

我想知道我做错了什么，因为我正在制作一个记忆游戏，但图像无法在我的画布上绘制。

    var ctx; 
    var cardBacks = "Resources/monster.png"; //shows back of card when turned over
    var faces = []; 
    var tiles = [];
    var Tile;
    var columns = 5;
    var rows = 4;
    function createTile(x,y){
        this.x = x;
        this.y = y;
        this.width = 70;
        ctx.drawImage(cardBacks, this.x, this.y, this.width, this.width);
    }
    function initialize(){
        ctx = document.getElementById("myCanvas").getContext("2d");
        for (var i = 0; i < columns; i++) {
            for (var j = 0; j < rows; j++) {
                tiles.push(createTile(i * 78 + 10, j * 78 + 40));
            }
        }
    }

Answer 1

尝试使用加载回调函数编写此代码。

var ctx;
var cardBacks = new Image();
cardBacks.src = "Resources/monster.png"; //shows back of card when turned over
cardBacks.onload = function() {
    ctx.drawImage(cardBacks, this.x, this.y, this.width, this.width);
}
var faces = [];
var tiles = [];
var Tile;
var columns = 5;
var rows = 4;
function createTile(x, y) {
    this.x = x;
    this.y = y;
    this.width = 70;
}
function initialize() {
    ctx = document.getElementById("myCanvas").getContext("2d");
    for (var i = 0; i < columns; i++) {
        for (var j = 0; j < rows; j++) {
            tiles.push(createTile(i * 78 + 10, j * 78 + 40));
        }
    }
}

Answer 2

您需要在画布上绘制HTML图像元素，而不是URL。我想你可以做到

var cardBacks = new Image();
cardBacks.src = "Resources/monster.png";

下面是一个示例：https://jsfiddle.net/yarhqskx/
这是多个（添加加载）： https://jsfiddle.net/yarhqskx/7/