如何从数组中的图像源创建Canvas图像？

问题描述

我想从来自我的ajax请求的数组中的多个图像创建一个Canvas图像;为此我尝试运行循环，但 drawImage 不适用于循环。

I want to create a Canvas image from multiple images in an array coming from my ajax request; for that purpose i try to run the loop but drawImage does not works with the loop.

然后我尝试了函数，并在循环中调用该函数，但同样的事情发生 drawImage 不适用于此

Then i try a function, and called that function in a loop but same thing happens drawImage does not works with this

下面我有提到了所有带有loop&功能的代码之一一个目前正在工作的 drawImage 中的静态信息。

below i have mentioned all the code one with the function one with the loop & one with static information in drawImage which is currently working.

如果你们中的任何人，我真的很感激请指导我如何解决此问题。

静态drawImage代码哪个正常工作

function loadImages(sources, callback, imagesrc) {
        var images = {};
        var loadedImages = 0;
        var numImages = 0;

        for(var src in sources) {
          numImages++;
        }

        for(var src in sources) {
          images[src] = new Image();
          images[src].onload = function() {
            if(++loadedImages >= numImages) {
              callback(images);
            }
          };
          images[src].src = sources[src];
        }


 }

      var canvas = document.getElementById('product-image');

      canvas.height = (jQuery(window).height()) -120;
      canvas.width = canvas.height * 0.75;
      var heightscreen = (jQuery(window).height()) -120;
      var canvasheight = heightscreen;
      var canvaswidth = canvas.height * 0.75;
      canvaswidthdiv4 = 0;
      var widthNeeded = canvasheight * 0.75;

      var context = canvas.getContext('2d');

// THIS IS A DUMMY ARRAY SAME AS COME IN AJAX RESPONSE
        var sources =
        {
        Slim_Fit: "http://localhost/plugindev/wp-content/uploads/2015/08/slimFit.png",
        Inside_Colar: "http://localhost/plugindev/wp-content/uploads/2015/08/maincolar.png",
        Outside_Colar: "http://localhost/plugindev/wp-content/uploads/2015/08/outer_collar1.png",
        Main_Colar: "http://localhost/plugindev/wp-content/uploads/2015/08/inner_collar11.png"
        };



      loadImages(sources, function(images)
      {

        context.drawImage(images.Slim_Fit, canvaswidthdiv4, 55, widthNeeded, canvasheight);
        context.drawImage(images.Inside_Colar, canvaswidthdiv4, 55, widthNeeded, canvasheight);
        context.drawImage(images.Outside_Colar, canvaswidthdiv4, 55, widthNeeded, canvasheight);
        context.drawImage(images.Main_Colar, canvaswidthdiv4, 55, widthNeeded, canvasheight);

      });

以下是我用于功能但不起作用的修正

 loadImages(sources, function(images)
  {
jQuery.each( sources, function( key, value ) {

 DrawImage(key, images );

  });

  });

function DrawImage(keyname,images){

context.drawImage(images.keyname, canvaswidthdiv4, 55, widthNeeded, canvasheight);
        }

以下是我使用循环绘制时的修正，但这是不工作

 loadImages(sources, function(images)
  {
jQuery.each( sources, function( key, value ) {

 context.drawImage(images.key, canvaswidthdiv4, 55, widthNeeded, canvasheight);

  });

  });

请帮忙！

推荐答案

注意，出现问题的 js 会将先前绘制的图像上的每个图像绘制到 canvas 第二，第三，第四个参数 .drawImage loadImages ？

Note, js at Question appear drawing each image over previously drawn image onto canvas at second, third, fourth arguments to .drawImage within loadImages ?

loadImages(sources, function(images)
      {
        context.drawImage(images.Slim_Fit, canvaswidthdiv4, 55, widthNeeded, canvasheight);
        context.drawImage(images.Inside_Colar, canvaswidthdiv4, 55, widthNeeded, canvasheight);
        context.drawImage(images.Outside_Colar, canvaswidthdiv4, 55, widthNeeded, canvasheight);
        context.drawImage(images.Main_Colar, canvaswidthdiv4, 55, widthNeeded, canvasheight);

      });

请注意来源

// THIS IS A DUMMY ARRAY SAME AS COME IN AJAX RESPONSE
        var sources =
        {
        Slim_Fit: "http://localhost/plugindev/wp-content/uploads/2015/08/slimFit.png",
        Inside_Colar: "http://localhost/plugindev/wp-content/uploads/2015/08/maincolar.png",
        Outside_Colar: "http://localhost/plugindev/wp-content/uploads/2015/08/outer_collar1.png",
        Main_Colar: "http://localhost/plugindev/wp-content/uploads/2015/08/inner_collar11.png"
        };

是对象，不是数组

js 可以缩短为单个 .forEach（）循环;在 .forEach .drawImage 时根据需要调整 canvas 的位置$ c>回调

js could be shortened to single .forEach() loop ; adjusting position on canvas as needed at call to .drawImage within .forEach callback

var canvas = document.getElementById("product-image");
/*
canvas.height = (jQuery(window).height()) - 120;
canvas.width = canvas.height * 0.75;
var heightscreen = (jQuery(window).height()) - 120;
var canvasheight = heightscreen;
var canvaswidth = canvas.height * 0.75;
canvaswidthdiv4 = 0;
var widthNeeded = canvasheight * 0.75;
*/

var context = canvas.getContext('2d');

var images = ["http://lorempixel.com/50/50/cats"
              , "http://lorempixel.com/50/50/nature"
              , "http://lorempixel.com/50/50/animals"
              , "http://lorempixel.com/50/50/sports"
];

images.forEach(function(src, index) {
  var img = new Image;
  img.onload = function() {
    context.drawImage(this, index * this.width, index * this.width)
  }
  img.src = src
})

<canvas id="product-image" width="400px" height="400px"></canvas>

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