Question

嘿，我真的希望有人帮助我。所以，基本上我只是尝试我的画布技巧。我想制作一个射击游戏，我在一堆表情符号上拍摄不同的y轴点，不同的高度，并在x轴上以不同的速度滑动。

我有一些emogi图像，我将它们重命名为enumrable。我努力的地方是在弧内显示图像。此外，我希望整个图像以10 x 10 /等显示，而不仅仅是溢出它。

我真的希望有人帮助我，谢谢。

var canvas = document.querySelector('canvas');
var ctx = canvas.getContext('2d');
var height = canvas.height = window.innerHeight;
var width = canvas.width = window.innerWidth;
function random(min, max) {
    var num = Math.floor(Math.random() * (max - min)) + min;
    if (num === 0) {
       return 2;
    }
    return num;
}
function Target(x, y, velX, radius, image) {
    this.x = x;
    this.y = y;
    this.velX = velX;
    //this.velY = velY;
    this.radius = radius;
    this.image = image;
}
Target.prototype.update = function () {
    if (this.x + this.radius >= width) {
        this.velX = -this.velX;
    }
    if (this.x + this.radius <= width) {
        this.velX = -this.velX;
    }
    /*if (this.y + this.radius >= height) {
        this.velY = -this.velY;
    }
    if (this.y + this.radius >= 0) {
        this.velY = -this.velY;
    }*/
    this.x += this.velX;
    //this.y += this.velY; 
};
Target.prototype.draw = function () {
    ctx.beginPath();
    ctx.arc(this.x, this.y, this.radius, 0, 2 * Math.PI, true);
    ctx.fillStyle = ctx.createPattern(this.image, 'no-repeat');
    ctx.fill();


    this.update();
};


//var target1 = new Target(30, 40, 20, 20);
function loop() {
    ctx.fillRect(0, 0, width, height);
    var targets = [];
    var img = new Image();
    while (targets.length < 25) {
        img.src = './images/emogi' + random(1, 6) + '.jpg';
        img.repeat = 'no-repeat';
        img.maxHeight = 10;
        img.maxWidth = 10;
        var target = new Target(
            random(100, 500),
            random(100, 500),
            random(10, 30),
            20,
            img
        );
        targets.push(target);
    }
    for (var i =0; i< targets.length; i++) {
        target[i].draw();
        target[i].update();
    }
    requestAnimationFrame(loop);

}
loop();

Answer 1

您的问题是您没有看到图像。发生这种情况是因为您开始加载图像然后立即绘制它。画画时，没有图像。它尚未加载！

要修复它，您必须预加载所有图像

示例

Let images = {
    “emoji”: {}
};

function loadImages() {
    return new Promise((resolve, reject) => {
        // initiate loading
        // wait for all to load
        // resolve promise
    });
}

loadImages.then(startGame);

您可能会发现这个问题很有帮助 Javascript/HTML5 using image to fill canvas

试图将图像放在画布上的弧内 - javascript

1 个答案: