Javascript 父元素是否使用“引用”;显示:无“;是否导致未加载子imgs?
目前,我正在使用画布使用javascript动态生成灰度图像。 灰度代码如下所示:Javascript 父元素是否使用“引用”;显示:无“;是否导致未加载子imgs?,javascript,jquery,html,css,canvas,Javascript,Jquery,Html,Css,Canvas,目前,我正在使用画布使用javascript动态生成灰度图像。 灰度代码如下所示: // Grayscale w canvas method function grayscale(src) { var canvasUrl = false; try { var canvas = document.createElement('canvas'); var ctx = canvas.getContext('2d'); var i
// Grayscale w canvas method
function grayscale(src)
{
var canvasUrl = false;
try
{
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
var imgObj = new Image();
imgObj.src = src;
canvas.width = imgObj.width;
canvas.height = imgObj.height;
ctx.drawImage(imgObj, 0, 0);
var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);
for(var y = 0; y < imgPixels.height; y++){
for(var x = 0; x < imgPixels.width; x++){
var i = (y * 4) * imgPixels.width + x * 4;
var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
imgPixels.data[i] = avg;
imgPixels.data[i + 1] = avg;
imgPixels.data[i + 2] = avg;
}
}
ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
canvasUrl = canvas.toDataURL();
}
catch(err)
{
canvasUrl = false;
}
return canvasUrl;
}
基于这里的相关问题,一般的解决方案似乎是使用$(window).load(func)
以运行灰度生成代码
然而,这就是我正在做的:
<script type="text/javascript">
var animateTime = 250;
// On window load. This waits until images have loaded which is essential
$(window).load(function(){
// Fade in images so there isn't a color "pop" document load and then on window load
$(".item img").animate({opacity:1},animateTime);
// clone image
$('.item img').each(function(){
var el = $(this);
el.css({"position":"absolute"}).wrap("<div class='img_wrapper' style='display: inline-block'>").clone().addClass('img_grayscale').css({"position":"absolute","z-index":"998","opacity":"0"}).insertBefore(el).queue(function(){
var el = $(this);
el.parent().css({"width":el.css("width"),"height":el.css("height")});
el.dequeue();
});
this.src = grayscale(this.src);
if(!this.src)
alert('An error occurred.'); // handle the occasional DOM error...
});
// Fade image
$('.item img').mouseover(function(){
$(this).parent().find('img:first').stop().animate({opacity:1}, animateTime);
})
$('.img_grayscale').mouseout(function(){
$(this).stop().animate({opacity:0}, animateTime);
});
$('.item').mouseover(function() {
$(this).children('h3').css('display', 'block');
$(this).children('h3').stop().animate({opacity:1}, animateTime);
});
$('.item').mouseout(function() {
$(this).children('h3').css('display', 'none');
$(this).children('h3').stop();
$(this).children('h3').css('opacity', '0');
});
$("#loading").css('display', 'none'); // hide the loading GIF
$(".outer_content_container").css('display', 'block');
$(".outer_content_container").animate({opacity:1}, animateTime*4);
});
</script>
var animateTime=250;
//窗口加载。这将等待图像加载完成,这是必不可少的
$(窗口)。加载(函数(){
//淡入图像,这样就不会加载彩色“弹出”文档,然后再加载窗口
$(“.item img”).animate({opacity:1},animateTime);
//克隆图像
$('.item img')。每个(函数(){
var el=$(本);
css({“位置”:“绝对”}).wrap(“”.clone().addClass('img_grayscale').css({“位置”:“绝对”,“z索引”:“998”,“不透明度”:“0”}).insertBefore(el).queue(函数(){
var el=$(本);
el.parent().css({“宽度”:el.css(“宽度”),“高度”:el.css(“高度”)});
el.dequeue();
});
this.src=灰度(this.src);
如果(!this.src)
警报('发生错误');//处理偶尔出现的DOM错误。。。
});
//淡入图像
$('.item img').mouseover(函数(){
$(this.parent().find('img:first').stop().animate({opacity:1},animateTime);
})
$('.img_grayscale').mouseout(函数(){
$(this.stop().animate({opacity:0},animateTime);
});
$('.item').mouseover(函数(){
$(this).children('h3').css('display','block');
$(this.children('h3').stop().animate({opacity:1},animateTime);
});
$('.item').mouseout(函数(){
$(this).children('h3').css('display','none');
$(this.children('h3').stop();
$(this).children('h3').css('opacity','0');
});
$(“#加载”).css('display','none');//隐藏加载GIF
$(“.outer_content_container”).css('display','block');
$(“.outer\u content\u container”).animate({opacity:1},animateTime*4);
});
这让我想到:我在包含图像的父
div
上设置“display:none;”是否会导致浏览器根本不加载图像并继续调用window.onload?因为您有竞争条件,所以在加载图像之前不会设置图像的宽度和高度。使用onload事件了解何时可以读取尺寸
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
var imgObj = new Image();
imgObj.onload = function() {
//do the processing here
};
imgObj.src = src;
什么是加金
imgObj.src = src;
在该行之前,使用图像加载方法并将函数的其余部分包装在其中
imgObj.addEventListener("load", function() {
canvas.width = imgObj.width;
canvas.height = imgObj.height;gagein
ctx.drawImage(imgObj, 0, 0);
var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);
for(var y = 0; y < imgPixels.height; y++){
for(var x = 0; x < imgPixels.width; x++){
var i = (y * 4) * imgPixels.width + x * 4;
var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
imgPixels.data[i] = avg;
imgPixels.data[i + 1] = avg;
imgPixels.data[i + 2] = avg;
}
}
ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
canvasUrl = canvas.toDataURL();
}, false);
imgObj.addEventListener(“加载”,函数(){
canvas.width=imgObj.width;
canvas.height=imgObj.height;gagein
ctx.drawImage(imgObj,0,0);
var imgPixels=ctx.getImageData(0,0,canvas.width,canvas.height);
对于(变量y=0;y
设置图像“src”属性不会导致立即加载图像数据。您必须等待图像对象本身的“加载”事件。谢谢您的回答!似乎不再发生了。:)
imgObj.src = src;
imgObj.addEventListener("load", function() {
canvas.width = imgObj.width;
canvas.height = imgObj.height;gagein
ctx.drawImage(imgObj, 0, 0);
var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);
for(var y = 0; y < imgPixels.height; y++){
for(var x = 0; x < imgPixels.width; x++){
var i = (y * 4) * imgPixels.width + x * 4;
var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
imgPixels.data[i] = avg;
imgPixels.data[i + 1] = avg;
imgPixels.data[i + 2] = avg;
}
}
ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
canvasUrl = canvas.toDataURL();
}, false);